TY  - JOUR
A1  - Abdalla, Hassan E.
A1  - Abramowski, Attila
A1  - Aharonian, Felix A.
A1  - Benkhali, Faical  Ait
A1  - Akhperjanian, A. G.
A1  - Andersson, T.
A1  - Angüner, Ekrem Oǧuzhan
A1  - Arrieta, M.
A1  - Aubert, Pierre
A1  - Backes, Michael
A1  - Balzer, Arnim
A1  - Barnard, Michelle
A1  - Becherini, Yvonne
A1  - Tjus, J. Becker
A1  - Berge, David
A1  - Bernhard, Sabrina
A1  - Bernlöhr, K.
A1  - Birsin, E.
A1  - Blackwell, R.
A1  - Boettcher, Markus
A1  - Boisson, Catherine
A1  - Bolmont, J.
A1  - Bordas, Pol
A1  - Bregeon, Johan
A1  - Brun, Francois
A1  - Brun, Pierre
A1  - Bryan, Mark
A1  - Bulik, Tomasz
A1  - Capasso, M.
A1  - Carr, John
A1  - Casanova, Sabrina
A1  - Chakraborty, N.
A1  - Chalme-Calvet, R.
A1  - Chaves, Ryan C. G.
A1  - Chen, Andrew
A1  - Chevalier, J.
A1  - Chretien, M.
A1  - Colafrancesco, Sergio
A1  - Cologna, Gabriele
A1  - Condon, B.
A1  - Conrad, Jan
A1  - Couturier, C.
A1  - Cui, Y.
A1  - Davids, I. D.
A1  - Degrange, B.
A1  - Deil, C.
A1  - Devin, J.
A1  - de Wilt, P.
A1  - Djannati-Ataie, A.
A1  - Domainko, W.
A1  - Donath, A.
A1  - Dubus, G.
A1  - Dutson, K.
A1  - Dyks, J.
A1  - Dyrda, M.
A1  - Edwards, T.
A1  - Egberts, Kathrin
A1  - Eger, P.
A1  - Ernenwein, J. -P.
A1  - Eschbach, S.
A1  - Farnier, C.
A1  - Fegan, S.
A1  - Fernandes, M. V.
A1  - Fiasson, A.
A1  - Fontaine, G.
A1  - Foerster, A.
A1  - Funk, S.
A1  - Fuessling, M.
A1  - Gabici, S.
A1  - Gajdus, M.
A1  - Gallant, Y. A.
A1  - Garrigoux, T.
A1  - Giavitto, G.
A1  - Giebels, B.
A1  - Glicenstein, J. F.
A1  - Gottschall, D.
A1  - Goyal, A.
A1  - Grondin, M. -H.
A1  - Grudzinska, M.
A1  - Hadasch, D.
A1  - Hahn, J.
A1  - Hawkes, J.
A1  - Heinzelmann, G.
A1  - Henri, G.
A1  - Hermann, G.
A1  - Hervet, O.
A1  - Hillert, A.
A1  - Hinton, James Anthony
A1  - Hofmann, W.
A1  - Hoischen, Clemens
A1  - Holler, M.
A1  - Horns, D.
A1  - Ivascenko, A.
A1  - Jacholkowska, A.
A1  - Jamrozy, M.
A1  - Janiak, M.
A1  - Jankowsky, D.
A1  - Jankowsky, F.
A1  - Jingo, M.
A1  - Jogler, T.
A1  - Jouvin, L.
A1  - Jung-Richardt, I.
A1  - Kastendieck, M. A.
A1  - Katarzynski, K.
A1  - Katz, U.
A1  - Kerszberg, D.
A1  - Khelifi, B.
A1  - Kieffer, M.
A1  - King, J.
A1  - Klepser, S.
A1  - Klochkov, D.
A1  - Kluzniak, W.
A1  - Kolitzus, D.
A1  - Komin, Nu.
A1  - Kosack, K.
A1  - Krakau, S.
A1  - Kraus, M.
A1  - Krayzel, F.
A1  - Krueger, P. P.
A1  - Laffon, H.
A1  - Lamanna, G.
A1  - Lau, J.
A1  - Lees, J. -P.
A1  - Lefaucheur, J.
A1  - Lefranc, V.
A1  - Lemiere, A.
A1  - Lemoine-Goumard, M.
A1  - Lenain, J. -P.
A1  - Leser, Eva
A1  - Liu, R.
A1  - Lohse, T.
A1  - Lorentz, M.
A1  - Lypova, I.
A1  - Marandon, V.
A1  - Marcowith, Alexandre
A1  - Mariaud, C.
A1  - Marx, R.
A1  - Maurin, G.
A1  - Maxted, N.
A1  - Mayer, Michael
A1  - Meintjes, P. J.
A1  - Meyer, M.
A1  - Mitchell, A. M. W.
A1  - Moderski, R.
A1  - Mohamed, M.
A1  - Mora, K.
A1  - Moulin, Emmanuel
A1  - Murach, T.
A1  - de Naurois, M.
A1  - Niederwanger, F.
A1  - Niemiec, J.
A1  - Oakes, L.
A1  - Odaka, H.
A1  - Ohm, S.
A1  - Ostrowski, M.
A1  - Oettl, S.
A1  - Oya, I.
A1  - Padovani, M.
A1  - Panter, M.
A1  - Parsons, R. D.
A1  - Arribas, M. Paz
A1  - Pekeur, N. W.
A1  - Pelletier, G.
A1  - Perennes, C.
A1  - Petrucci, P. -O.
A1  - Peyaud, B.
A1  - Pita, S.
A1  - Poon, H.
A1  - Prokhorov, D.
A1  - Prokoph, H.
A1  - Puehlhofer, G.
A1  - Punch, M.
A1  - Quirrenbach, A.
A1  - Raab, S.
A1  - Reimer, A.
A1  - Reimer, O.
A1  - Renaud, M.
A1  - Reyes, R. de los
A1  - Rieger, F.
A1  - Romoli, C.
A1  - Rosier-Lees, S.
A1  - Rowell, G.
A1  - Rudak, B.
A1  - Rulten, C. B.
A1  - Sahakian, V.
A1  - Salek, D.
A1  - Sanchez, David M.
A1  - Santangelo, A.
A1  - Sasaki, M.
A1  - Schlickeiser, R.
A1  - Schuessler, F.
A1  - Schulz, A.
A1  - Schwanke, U.
A1  - Schwemmer, S.
A1  - Settimo, M.
A1  - Seyffert, A. S.
A1  - Shafi, N.
A1  - Shilon, I.
A1  - Simoni, R.
A1  - Sol, H.
A1  - Spanier, F.
A1  - Spengler, G.
A1  - Spies, F.
A1  - Stawarz, L.
A1  - Steenkamp, R.
A1  - Stegmann, Christian
A1  - Stinzing, F.
A1  - Stycz, K.
A1  - Sushch, Iurii
A1  - Tavernet, J. -P.
A1  - Tavernier, T.
A1  - Taylor, A. M.
A1  - Terrier, R.
A1  - Tibaldo, L.
A1  - Tluczykont, M.
A1  - Trichard, C.
A1  - Tuffs, R.
A1  - van der Walt, J.
A1  - van Eldik, C.
A1  - van Soelen, B.
A1  - Vasileiadis, G.
A1  - Veh, J.
A1  - Venter, C.
A1  - Viana, A.
A1  - Vincent, P.
A1  - Vink, J.
A1  - Voisin, F.
A1  - Voelk, H. J.
A1  - Vuillaume, T.
A1  - Wadiasingh, Z.
A1  - Wagner, S. J.
A1  - Wagner, P.
A1  - Wagner, R. M.
A1  - White, R.
A1  - Wierzcholska, A.
A1  - Willmann, P.
A1  - Woernlein, A.
A1  - Wouters, D.
A1  - Yang, R.
A1  - Zabalza, V.
A1  - Zaborov, D.
A1  - Zacharias, M.
A1  - Zdziarski, A. A.
A1  - Zech, Alraune
A1  - Zefi, F.
A1  - Ziegler, A.
A1  - Zywucka, N.
T1  - HESS Limits on Linelike Dark Matter Signatures in the 100 GeV to 2 TeV Energy Range Close to the Galactic Center
JF  - Physical review letters
N2  - A search for dark matter linelike signals iss performed in the vicinity of the Galactic Center by the H.E.S.S. experiment on observational data taken in 2014. An unbinned likelihood analysis iss developed to improve the sensitivity to linelike signals. The upgraded analysis along with newer data extend the energy coverage of the previous measurement down to 100 GeV. The 18 h of data collected with the H.E.S.S. array allow one to rule out at 95% C.L. the presence of a 130 GeV line (at l = -1.5 degrees, b = 0 degrees and for a dark matter profile centered at this location) previously reported in Fermi-LAT data. This new analysis overlaps significantly in energy with previous Fermi-LAT and H.E.S.S. results. No significant excess associated with dark matter annihilations was found in the energy range of 100 GeV to 2 TeV and upper limits on the gamma-ray flux and the velocity weighted annihilation cross section are derived adopting an Einasto dark matter halo profile. Expected limits for present and future large statistics H.E.S.S. observations are also given.
Y1  - 2016
U6  - https://doi.org/10.1103/PhysRevLett.117.151302
SN  - 0031-9007
SN  - 1079-7114
VL  - 117
PB  - American Physical Society
CY  - College Park
ER  - 
TY  - JOUR
A1  - Abdalla, Hassan E.
A1  - Abramowski, Attila
A1  - Aharonian, Felix A.
A1  - Benkhali, Faiçal Ait
A1  - Akhperjanian, A. G.
A1  - Angüner, Ekrem Oǧuzhan
A1  - Arrieta, M.
A1  - Aubert, Pierre
A1  - Backes, Michael
A1  - Balzer, Arnim
A1  - Barnard, Michelle
A1  - Becherini, Yvonne
A1  - Tjus, Julia Becker
A1  - Berge, David
A1  - Bernhard, Sabrina
A1  - Bernlöhr, K.
A1  - Birsin, E.
A1  - Blackwell, R.
A1  - Bottcher, Markus
A1  - Boisson, Catherine
A1  - Bolmont, J.
A1  - Bordas, Pol
A1  - Bregeon, Johan
A1  - Brun, Francois
A1  - Brun, Pierre
A1  - Bryan, Mark
A1  - Bulik, Tomasz
A1  - Capasso, M.
A1  - Carr, John
A1  - Casanova, Sabrina
A1  - Chakraborty, N.
A1  - Chalme-Calvet, R.
A1  - Chaves, Ryan C. G.
A1  - Chen, Andrew
A1  - Chevalier, J.
A1  - Chretien, M.
A1  - Colafrancesco, Sergio
A1  - Cologna, Gabriele
A1  - Condon, B.
A1  - Conrad, Jan
A1  - Couturier, C.
A1  - Cui, Y.
A1  - Davids, I. D.
A1  - Degrange, B.
A1  - Deil, Christoph
A1  - deWilt, P.
A1  - Djannati-Atai, Arache
A1  - Domainko, Wilfried
A1  - Donath, Axel
A1  - Dubus, Guillaume
A1  - Dutson, Kate
A1  - Dyks, J.
A1  - Dyrda, M.
A1  - Edwards, T.
A1  - Egberts, Kathrin
A1  - Eger, P.
A1  - Ernenwein, J. -P.
A1  - Eschbach, S.
A1  - Farnier, C.
A1  - Fegan, Stuart
A1  - Fernandes, M. V.
A1  - Fiasson, A.
A1  - Fontaine, G.
A1  - Foerster, A.
A1  - Funk, S.
A1  - Füßling, Matthias
A1  - Gabici, Stefano
A1  - Gajdus, M.
A1  - Gallant, Y. A.
A1  - Garrigoux, T.
A1  - Giavitto, Gianluca
A1  - Giebels, B.
A1  - Glicenstein, J. F.
A1  - Gottschall, Daniel
A1  - Goyal, A.
A1  - Grondin, M. -H.
A1  - Grudzinska, M.
A1  - Hadasch, Daniela
A1  - Hahn, J.
A1  - Hawkes, J.
A1  - Heinzelmann, G.
A1  - Henri, Gilles
A1  - Hermann, G.
A1  - Hervet, Olivier
A1  - Hillert, A.
A1  - Hinton, James Anthony
A1  - Hofmann, Werner
A1  - Hoischen, Clemens
A1  - Holler, M.
A1  - Horns, D.
A1  - Ivascenko, Alex
A1  - Jacholkowska, A.
A1  - Jamrozy, Marek
A1  - Janiak, M.
A1  - Jankowsky, D.
A1  - Jankowsky, Felix
A1  - Jingo, M.
A1  - Jogler, Tobias
A1  - Jouvin, Lea
A1  - Jung-Richardt, Ira
A1  - Kastendieck, M. A.
A1  - Katarzynski, Krzysztof
A1  - Katz, Uli
A1  - Kerszberg, D.
A1  - Khelifi, B.
A1  - Kieffer, M.
A1  - King, J.
A1  - Klepser, S.
A1  - Klochkov, Dmitry
A1  - Kluzniak, W.
A1  - Kolitzus, D.
A1  - Komin, Nu.
A1  - Kosack, K.
A1  - Krakau, S.
A1  - Kraus, Michael
A1  - Krayzel, F.
A1  - Kruger, P. P.
A1  - Laffon, H.
A1  - Lamanna, G.
A1  - Lau, Jeanie
A1  - Lees, J. -P.
A1  - Lefaucheur, J.
A1  - Lefranc, V.
A1  - Lemiere, A.
A1  - Lemoine-Goumard, M.
A1  - Lenain, J. -P.
A1  - Leser, Eva
A1  - Lohse, Thomas
A1  - Lorentz, M.
A1  - Lui, R.
A1  - Lypova, Iryna
A1  - Marandon, Vincent
A1  - Marcowith, Alexandre
A1  - Mariaud, C.
A1  - Marx, R.
A1  - Maurin, G.
A1  - Maxted, N.
A1  - Mayer, Michael
A1  - Meintjes, Petrus Johannes
A1  - Menzler, U.
A1  - Meyer, Manuel
A1  - Mitchell, A. M. W.
A1  - Moderski, R.
A1  - Mohamed, M.
A1  - Mora, K.
A1  - Moulin, Emmanuel
A1  - Murach, T.
A1  - de Naurois, Mathieu
A1  - Niederwanger, F.
A1  - Niemiec, J.
A1  - Oakes, L.
A1  - Odaka, Hirokazu
A1  - Ohm, Stefan
A1  - Oettl, S.
A1  - Ostrowski, M.
A1  - Oya, I.
A1  - Padovani, Marco
A1  - Panter, M.
A1  - Parsons, R. D.
A1  - Arribas, M. Paz
A1  - Pekeur, N. W.
A1  - Pelletier, G.
A1  - Petrucci, P. -O.
A1  - Peyaud, B.
A1  - Pita, S.
A1  - Poon, Helen
A1  - Prokhorov, Dmitry
A1  - Prokoph, Heike
A1  - Puehlhofer, Gerd
A1  - Punch, Michael
A1  - Quirrenbach, Andreas
A1  - Raab, S.
A1  - Reimer, Anita
A1  - Reimer, Olaf
A1  - Renaud, M.
A1  - de los Reyes, R.
A1  - Rieger, Frank
A1  - Romoli, Carlo
A1  - Rosier-Lees, S.
A1  - Rowell, G.
A1  - Rudak, B.
A1  - Rulten, C. B.
A1  - Sahakian, V.
A1  - Salek, David
A1  - Sanchez, David A.
A1  - Santangelo, Andrea
A1  - Sasaki, Manami
A1  - Schlickeiser, Reinhard
A1  - Schussler, F.
A1  - Schulz, Andreas
A1  - Schwanke, U.
A1  - Schwemmer, S.
A1  - Seyffert, A. S.
A1  - Shafi, N.
A1  - Simoni, R.
A1  - Sol, H.
A1  - Spanier, Felix
A1  - Spengler, G.
A1  - Spiess, F.
A1  - Stawarz, Lukasz
A1  - Steenkamp, R.
A1  - Stegmann, Christian
A1  - Stinzing, F.
A1  - Stycz, K.
A1  - Sushch, Iurii
A1  - Tavernet, J. -P.
A1  - Tavernier, T.
A1  - Taylor, A. M.
A1  - Terrier, R.
A1  - Tluczykont, Martin
A1  - Trichard, C.
A1  - Tuffs, R.
A1  - van der Walt, Johan
A1  - van Eldik, Christopher
A1  - van Soelen, Brian
A1  - Vasileiadis, Georges
A1  - Veh, J.
A1  - Venter, C.
A1  - Viana, A.
A1  - Vincent, P.
A1  - Vink, Jacco
A1  - Voisin, F.
A1  - Voelk, Heinrich J.
A1  - Vuillaume, Thomas
A1  - Wadiasingh, Z.
A1  - Wagner, Stefan J.
A1  - Wagner, P.
A1  - Wagner, R. M.
A1  - White, R.
A1  - Wierzcholska, Alicja
A1  - Willmann, P.
A1  - Woernlein, A.
A1  - Wouters, Denis
A1  - Yang, R.
A1  - Zabalza, Victor
A1  - Zaborov, D.
A1  - Zacharias, M.
A1  - Zdziarski, A. A.
A1  - Zech, Andreas
A1  - Zefi, F.
A1  - Ziegler, A.
A1  - Zywucka, Natalia
T1  - Search for Dark Matter Annihilations towards the Inner Galactic Halo from 10 Years of Observations with HESS
JF  - Physical review letters
N2  - The inner region of the Milky Way halo harbors a large amount of dark matter (DM). Given its proximity, it is one of the most promising targets to look for DM. We report on a search for the annihilations of DM particles using gamma-ray observations towards the inner 300 pc of the Milky Way, with the H.E.S.S. array of ground-based Cherenkov telescopes. The analysis is based on a 2D maximum likelihood method using Galactic Center (GC) data accumulated by H.E.S.S. over the last 10 years (2004-2014), and does not show any significant gamma-ray signal above background. Assuming Einasto and Navarro-Frenk-White DM density profiles at the GC, we derive upper limits on the annihilation cross section <sigma nu >. These constraints are the strongest obtained so far in the TeV DM mass range and improve upon previous limits by a factor 5. For the Einasto profile, the constraints reach <sigma nu > values of 6 x 10(-26) cm(3) s(-1) in the W+W- channel for a DM particle mass of 1.5 TeV, and 2 x 10(-26) cm(3) s(-1) in the tau(+)tau(-) channel for a 1 TeV mass. For the first time, ground-based gamma-ray observations have reached sufficient sensitivity to probe <sigma nu > values expected from the thermal relic density for TeV DM particles.
Y1  - 2016
U6  - https://doi.org/10.1103/PhysRevLett.117.111301
SN  - 0031-9007
SN  - 1079-7114
VL  - 117
PB  - American Physical Society
CY  - College Park
ER  - 
TY  - JOUR
A1  - Abeysekara, A. U.
A1  - Archambault, S.
A1  - Archer, A.
A1  - Benbow, W.
A1  - Bird, R.
A1  - Biteau, Jonathan
A1  - Buchovecky, M.
A1  - Buckley, J. H.
A1  - Bugaev, V.
A1  - Byrum, K.
A1  - Cardenzana, J. V.
A1  - Cerruti, M.
A1  - Chen, Xuhui
A1  - Christiansen, J. L.
A1  - Ciupik, L.
A1  - Connolly, M. P.
A1  - Cui, W.
A1  - Dickinson, H. J.
A1  - Dumm, J.
A1  - Eisch, J. D.
A1  - Errando, M.
A1  - Falcone, A.
A1  - Feng, Q.
A1  - Finley, J. P.
A1  - Fleischhack, H.
A1  - Flinders, A.
A1  - Fortin, P.
A1  - Fortson, L.
A1  - Furniss, A.
A1  - Gillanders, G. H.
A1  - Griffin, S.
A1  - Grube, J.
A1  - Gyuk, G.
A1  - Huetten, M.
A1  - Hanna, D.
A1  - Holder, J.
A1  - Humensky, T. B.
A1  - Johnson, C. A.
A1  - Kaaret, P.
A1  - Kar, P.
A1  - Kelley-Hoskins, N.
A1  - Kertzman, M.
A1  - Kieda, D.
A1  - Krause, M.
A1  - Krennrich, F.
A1  - Lang, M. J.
A1  - Maier, G.
A1  - McArthur, S.
A1  - McCann, A.
A1  - Meagher, K.
A1  - Moriarty, P.
A1  - Mukherjee, R.
A1  - Nieto, D.
A1  - Ong, R. A.
A1  - Otte, A. N.
A1  - Park, N.
A1  - Pelassa, V.
A1  - Petrashyk, A.
A1  - Petry, D.
A1  - Pohl, Martin
A1  - Popkow, A.
A1  - Pueschel, Elisa
A1  - Quinn, J.
A1  - Ragan, K.
A1  - Ratliff, G.
A1  - Reyes, L. C.
A1  - Reynolds, P. T.
A1  - Reynolds, K.
A1  - Richards, G. T.
A1  - Roache, E.
A1  - Rulten, C.
A1  - Santander, M.
A1  - Sembroski, G. H.
A1  - Shahinyan, K.
A1  - Smith, A. W.
A1  - Staszak, D.
A1  - Telezhinsky, Igor O.
A1  - Tucci, J. V.
A1  - Tyler, J.
A1  - Vincent, S.
A1  - Wakely, S. P.
A1  - Weiner, O. M.
A1  - Weinstein, A.
A1  - Wilhelm, Alina
A1  - Williams, D. A.
A1  - Zitzer, B.
T1  - VERITAS and multiwavelength observations of the BL Lacertae object 1ES 1741+196
JF  - Monthly notices of the Royal Astronomical Society
N2  - We present results from multiwavelength observations of the BL Lacertae object 1ES 1741 + 196, including results in the very high energy gamma-ray regime using the Very Energetic Radiation Imaging Telescope Array System (VERITAS). The VERITAS time-averaged spectrum, measured above 180 GeV, is well modelled by a power law with a spectral index of 2.7 +/- 0.7(stat) +/- 0.2(syst). The integral flux above 180 GeV is (3.9 +/- 0.8(stat) +/- 1.0(syst)) x 10(-8) m(-2) s(-1), corresponding to 1.6 per cent of the Crab nebula flux on average. The multiwavelength spectral energy distribution of the source suggests that 1ES 1741+196 is an extreme-high-frequency-peaked BL Lacertae object. The observations analysed in this paper extend over a period of six years, during which time no strong flares were observed in any band. This analysis is therefore one of the few characterizations of a blazar in a non-flaring state.
KW  - astroparticle physics
KW  - relativistic processes
KW  - galaxies: individual: 1ES 1741+196=VER J1744+195
Y1  - 2016
U6  - https://doi.org/10.1093/mnras/stw664
SN  - 0035-8711
SN  - 1365-2966
VL  - 459
SP  - 2550
EP  - 2557
PB  - Oxford Univ. Press
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Abeysekara, A. U.
A1  - Archambault, S.
A1  - Archer, A.
A1  - Benbow, W.
A1  - Bird, R.
A1  - Buchovecky, M.
A1  - Buckley, J. H.
A1  - Byrum, K.
A1  - Cardenzana, J. V.
A1  - Cerruti, M.
A1  - Chen, Xuhui
A1  - Christiansen, J. L.
A1  - Ciupik, L.
A1  - Cui, W.
A1  - Dickinson, H. J.
A1  - Eisch, J. D.
A1  - Errando, M.
A1  - Falcone, A.
A1  - Fegan, D. J.
A1  - Feng, Q.
A1  - Finley, J. P.
A1  - Fleischhack, H.
A1  - Fortin, P.
A1  - Fortson, L.
A1  - Furniss, A.
A1  - Gillanders, G. H.
A1  - Griffin, S.
A1  - Grube, J.
A1  - Gyuk, G.
A1  - Huetten, M.
A1  - Hakansson, Nils
A1  - Hanna, D.
A1  - Holder, J.
A1  - Humensky, T. B.
A1  - Johnson, C. A.
A1  - Kaaret, P.
A1  - Kar, P.
A1  - Kelley-Hoskins, N.
A1  - Kertzman, M.
A1  - Kieda, D.
A1  - Krause, M.
A1  - Krennrich, F.
A1  - Kumar, S.
A1  - Lang, M. J.
A1  - Lin, T. T. Y.
A1  - Maier, G.
A1  - McArthur, S.
A1  - McCann, A.
A1  - Meagher, K.
A1  - Moriarty, P.
A1  - Mukherjee, R.
A1  - Nieto, D.
A1  - Ong, R. A.
A1  - Otte, A. N.
A1  - Park, N.
A1  - Perkins, J. S.
A1  - Petrashyk, A.
A1  - Pohl, Martin
A1  - Popkow, A.
A1  - Pueschel, Elisa
A1  - Quinn, J.
A1  - Ragan, K.
A1  - Ratliff, G.
A1  - Reynolds, P. T.
A1  - Richards, G. T.
A1  - Roache, E.
A1  - Santander, M.
A1  - Sembroski, G. H.
A1  - Shahinyan, K.
A1  - Staszak, D.
A1  - Telezhinsky, Igor O.
A1  - Tucci, J. V.
A1  - Tyler, J.
A1  - Vincent, S.
A1  - Wakely, S. P.
A1  - Weiner, O. M.
A1  - Weinstein, A.
A1  - Williams, D. A.
A1  - Zitzer, B.
T1  - A SEARCH FOR BRIEF OPTICAL FLASHES ASSOCIATED WITH THE SETI TARGET KIC 8462852
JF  - The astrophysical journal : an international review of spectroscopy and astronomical physics ; Part 2, Letters
N2  - The F-type star KIC. 8462852 has recently been identified as an exceptional target for search for extraterrestrial intelligence (SETI) observations. We describe an analysis methodology for optical SETI, which we have used to analyze nine hours of serendipitous archival observations of KIC. 8462852 made with the VERITAS gamma-ray observatory between 2009 and 2015. No evidence of pulsed optical beacons, above a pulse intensity at the Earth of approximately 1 photon m(-2), is found. We also discuss the potential use of imaging atmospheric Cherenkov telescope arrays in searching for extremely short duration optical transients in general.
KW  - astrobiology
KW  - extraterrestrial intelligence
KW  - methods: observational
KW  - stars: individual ( KIC 8462852)
KW  - techniques: photometric
Y1  - 2016
U6  - https://doi.org/10.3847/2041-8205/818/2/L33
SN  - 2041-8205
SN  - 2041-8213
VL  - 818
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Abramowski, Attila
A1  - Aharonian, Felix A.
A1  - Benkhali, Faical  Ait
A1  - Akhperjanian, A. G.
A1  - Angüner, Ekrem Oǧuzhan
A1  - Backes, Michael
A1  - Balzer, Arnim
A1  - Becherini, Yvonne
A1  - Tjus, J. Becker
A1  - Berge, David
A1  - Bernhard, Sabrina
A1  - Bernlöhr, K.
A1  - Birsin, E.
A1  - Blackwell, R.
A1  - Boettcher, Markus
A1  - Boisson, Catherine
A1  - Bolmont, J.
A1  - Bordas, Pol
A1  - Bregeon, Johan
A1  - Brun, Francois
A1  - Brun, Pierre
A1  - Bryan, Mark
A1  - Bulik, Tomasz
A1  - Carr, John
A1  - Casanova, Sabrina
A1  - Chakraborty, N.
A1  - Chalme-Calvet, R.
A1  - Chaves, Ryan C. G.
A1  - Chen, Andrew
A1  - Chretien, M.
A1  - Colafrancesco, Sergio
A1  - Cologna, Gabriele
A1  - Conrad, Jan
A1  - Couturier, C.
A1  - Cui, Y.
A1  - Davids, I. D.
A1  - Degrange, B.
A1  - Deil, C.
A1  - deWilt, P.
A1  - Djannati-Ata, A.
A1  - Domainko, W.
A1  - Donath, A.
A1  - Dubus, G.
A1  - Dutson, K.
A1  - Dyks, J.
A1  - Dyrda, M.
A1  - Edwards, T.
A1  - Egberts, Kathrin
A1  - Eger, P.
A1  - Ernenwein, J-P.
A1  - Espigat, P.
A1  - Farnier, C.
A1  - Fegan, S.
A1  - Feinstein, F.
A1  - Fernandes, M. V.
A1  - Fernandez, D.
A1  - Fiasson, A.
A1  - Fontaine, G.
A1  - Foerster, A.
A1  - Fuessling, M.
A1  - Gabici, S.
A1  - Gajdus, M.
A1  - Gallant, Y. A.
A1  - Garrigoux, T.
A1  - Giavitto, G.
A1  - Giebels, B.
A1  - Glicenstein, J. F.
A1  - Gottschall, D.
A1  - Goyal, A.
A1  - Grondin, M-H.
A1  - Grudzinska, M.
A1  - Hadasch, D.
A1  - Haeffner, S.
A1  - Hahn, J.
A1  - Hawkes, J.
A1  - Heinzelmann, G.
A1  - Henri, G.
A1  - Hermann, G.
A1  - Hervet, O.
A1  - Hillert, A.
A1  - Hinton, James Anthony
A1  - Hofmann, W.
A1  - Hofverberg, P.
A1  - Hoischen, Clemens
A1  - Holler, M.
A1  - Horns, D.
A1  - Ivascenko, A.
A1  - Jacholkowska, A.
A1  - Jamrozy, M.
A1  - Janiak, M.
A1  - Jankowsky, F.
A1  - Jung-Richardt, I.
A1  - Kastendieck, M. A.
A1  - Katarzynski, K.
A1  - Katz, U.
A1  - Kerszberg, D.
A1  - Khelifi, B.
A1  - Kieffer, M.
A1  - Klepser, S.
A1  - Klochkov, D.
A1  - Kluzniak, W.
A1  - Kolitzus, D.
A1  - Komin, Nu.
A1  - Kosack, K.
A1  - Krakau, S.
A1  - Krayzel, F.
A1  - Krueger, P. P.
A1  - Laffon, H.
A1  - Lamanna, G.
A1  - Lau, J.
A1  - Lefaucheur, J.
A1  - Lefranc, V.
A1  - Lemiere, A.
A1  - Lemoine-Goumard, M.
A1  - Lenain, J-P.
A1  - Lohse, T.
A1  - Lopatin, A.
A1  - Lu, C-C.
A1  - Lui, R.
A1  - Marandon, V.
A1  - Marcowith, Alexandre
A1  - Mariaud, C.
A1  - Marx, R.
A1  - Maurin, G.
A1  - Maxted, N.
A1  - Mayer, M.
A1  - Meintjes, P. J.
A1  - Menzler, U.
A1  - Meyer, M.
A1  - Mitchell, A. M. W.
A1  - Moderski, R.
A1  - Mohamed, M.
A1  - Mora, K.
A1  - Moulin, Emmanuel
A1  - Murach, T.
A1  - de Naurois, M.
A1  - Niemiec, J.
A1  - Oakes, L.
A1  - Odaka, H.
A1  - Oettl, S.
A1  - Ohm, S.
A1  - Opitz, B.
A1  - Ostrowski, M.
A1  - Oya, I.
A1  - Panter, M.
A1  - Parsons, R. D.
A1  - Arribas, M. Paz
A1  - Pekeur, N. W.
A1  - Pelletier, G.
A1  - Petrucci, P-O.
A1  - Peyaud, B.
A1  - Pita, S.
A1  - Poon, H.
A1  - Prokoph, H.
A1  - Puehlhofer, G.
A1  - Punch, M.
A1  - Quirrenbach, A.
A1  - Raab, S.
A1  - Reichardt, I.
A1  - Reimer, A.
A1  - Reimer, O.
A1  - Renaud, M.
A1  - de los Reyes, R.
A1  - Rieger, F.
A1  - Romoli, C.
A1  - Rosier-Lees, S.
A1  - Rowell, G.
A1  - Rudak, B.
A1  - Rulten, C. B.
A1  - Sahakian, V.
A1  - Salek, D.
A1  - Sanchez, David M.
A1  - Santangelo, A.
A1  - Sasaki, M.
A1  - Schlickeiser, R.
A1  - Schuessler, F.
A1  - Schulz, A.
A1  - Schwanke, U.
A1  - Schwemmer, S.
A1  - Seyffert, A. S.
A1  - Simoni, R.
A1  - Sol, H.
A1  - Spanier, F.
A1  - Spengler, G.
A1  - Spies, F.
A1  - Stawarz, L.
A1  - Steenkamp, R.
A1  - Stegmann, Christian
A1  - Stinzing, F.
A1  - Stycz, K.
A1  - Sushch, Iurii
A1  - Tavernet, J-P.
A1  - Tavernier, T.
A1  - Taylor, A. M.
A1  - Terrier, R.
A1  - Tluczykont, M.
A1  - Trichard, C.
A1  - Tuffs, R.
A1  - Valerius, K.
A1  - van der Walt, J.
A1  - van Eldik, C.
A1  - van Soelen, B.
A1  - Vasileiadis, G.
A1  - Veh, J.
A1  - Venter, C.
A1  - Viana, A.
A1  - Vincent, P.
A1  - Vink, J.
A1  - Voisin, F.
A1  - Voelk, H. J.
A1  - Vuillaume, T.
A1  - Wagner, S. J.
A1  - Wagner, P.
A1  - Wagner, R. M.
A1  - Weidinger, M.
A1  - Weitzel, Q.
A1  - White, R.
A1  - Wierzcholska, A.
A1  - Willmann, P.
A1  - Woernlein, A.
A1  - Wouters, D.
A1  - Yang, R.
A1  - Zabalza, V.
A1  - Zaborov, D.
A1  - Zacharias, M.
A1  - Zdziarski, A. A.
A1  - Zech, Alraune
A1  - Zefi, F.
A1  - Zywucka, N.
T1  - Acceleration of petaelectronvolt protons in the Galactic Centre
JF  - Nature : the international weekly journal of science
N2  - Galactic cosmic rays reach energies of at least a few petaelectronvolts (of the order of 1015 electronvolts). This implies that our Galaxy contains petaelectronvolt accelerators (‘PeVatrons’), but all proposed models of Galactic cosmic-ray accelerators encounter difficulties at exactly these energies. Dozens of Galactic accelerators capable of accelerating particles to energies of tens of teraelectronvolts (of the order of 1013 electronvolts) were inferred from recent &#947;-ray observations3. However, none of the currently known accelerators—not even the handful of shell-type supernova remnants commonly believed to supply most Galactic cosmic rays—has shown the characteristic tracers of petaelectronvolt particles, namely, power-law spectra of &#947;-rays extending without a cut-off or a spectral break to tens of teraelectronvolts4. Here we report deep &#947;-ray observations with arcminute angular resolution of the region surrounding the Galactic Centre, which show the expected tracer of the presence of petaelectronvolt protons within the central 10 parsecs of the Galaxy. We propose that the supermassive black hole Sagittarius A* is linked to this PeVatron. Sagittarius A* went through active phases in the past, as demonstrated by X-ray outbursts5and an outflow from the Galactic Centre6. Although its current rate of particle acceleration is not sufficient to provide a substantial contribution to Galactic cosmic rays, Sagittarius A* could have plausibly been more active over the last 106–107 years, and therefore should be considered as a viable alternative to supernova remnants as a source of petaelectronvolt Galactic cosmic rays.
Y1  - 2016
U6  - https://doi.org/10.1038/nature17147
SN  - 0028-0836
SN  - 1476-4687
VL  - 531
SP  - 476
EP  - +
PB  - Nature Publ. Group
CY  - London
ER  - 
TY  - JOUR
A1  - Aldoretta, E. J.
A1  - St-Louis, N.
A1  - Richardson, N. D.
A1  - Moffat, Anthony F. J.
A1  - Eversberg, T.
A1  - Hill, G. M.
A1  - Shenar, Tomer
A1  - Artigau, E.
A1  - Gauza, B.
A1  - Knapen, J. H.
A1  - Kubat, Jiří
A1  - Kubatova, Brankica
A1  - Maltais-Tariant, R.
A1  - Munoz, M.
A1  - Pablo, H.
A1  - Ramiaramanantsoa, T.
A1  - Richard-Laferriere, A.
A1  - Sablowski, D. P.
A1  - Simon-Diaz, S.
A1  - St-Jean, L.
A1  - Bolduan, F.
A1  - Dias, F. M.
A1  - Dubreuil, P.
A1  - Fuchs, D.
A1  - Garrel, T.
A1  - Grutzeck, G.
A1  - Hunger, T.
A1  - Kuesters, D.
A1  - Langenbrink, M.
A1  - Leadbeater, R.
A1  - Li, D.
A1  - Lopez, A.
A1  - Mauclaire, B.
A1  - Moldenhawer, T.
A1  - Potter, M.
A1  - dos Santos, E. M.
A1  - Schanne, L.
A1  - Schmidt, J.
A1  - Sieske, H.
A1  - Strachan, J.
A1  - Stinner, E.
A1  - Stinner, P.
A1  - Stober, B.
A1  - Strandbaek, K.
A1  - Syder, T.
A1  - Verilhac, D.
A1  - Waldschlaeger, U.
A1  - Weiss, D.
A1  - Wendt, A.
T1  - An extensive spectroscopic time series of three Wolf-Rayet stars - I. The lifetime of large-scale structures in the wind of WR 134
JF  - Monthly notices of the Royal Astronomical Society
N2  - During the summer of 2013, a 4-month spectroscopic campaign took place to observe the variabilities in three Wolf-Rayet stars. The spectroscopic data have been analysed for WR 134 (WN6b), to better understand its behaviour and long-term periodicity, which we interpret as arising from corotating interaction regions (CIRs) in the wind. By analysing the variability of the He ii lambda 5411 emission line, the previously identified period was refined to P = 2.255 +/- 0.008 (s.d.) d. The coherency time of the variability, which we associate with the lifetime of the CIRs in the wind, was deduced to be 40 +/- 6 d, or similar to 18 cycles, by cross-correlating the variability patterns as a function of time. When comparing the phased observational grey-scale difference images with theoretical grey-scales previously calculated from models including CIRs in an optically thin stellar wind, we find that two CIRs were likely present. A separation in longitude of Delta I center dot a parts per thousand integral 90A degrees was determined between the two CIRs and we suggest that the different maximum velocities that they reach indicate that they emerge from different latitudes. We have also been able to detect observational signatures of the CIRs in other spectral lines (C iv lambda lambda 5802,5812 and He i lambda 5876). Furthermore, a DAC was found to be present simultaneously with the CIR signatures detected in the He i lambda 5876 emission line which is consistent with the proposed geometry of the large-scale structures in the wind. Small-scale structures also show a presence in the wind, simultaneously with the larger scale structures, showing that they do in fact co-exist.
KW  - instabilities
KW  - methods: data analysis
KW  - techniques: spectroscopic
KW  - stars: individual: WR 134
KW  - stars: massive
KW  - stars: Wolf-Rayet
Y1  - 2016
U6  - https://doi.org/10.1093/mnras/stw1188
SN  - 0035-8711
SN  - 1365-2966
VL  - 460
SP  - 3407
EP  - 3417
PB  - Oxford Univ. Press
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Aliu, E.
A1  - Archambault, S.
A1  - Archer, A.
A1  - Arlen, T.
A1  - Aune, T.
A1  - Barnacka, Anna
A1  - Behera, B.
A1  - Beilicke, M.
A1  - Benbow, W.
A1  - Berger, K.
A1  - Bird, R.
A1  - Böttcher, Markus
A1  - Bouvier, A.
A1  - Buchovecky, M.
A1  - Buckley, J. H.
A1  - Bugaev, V.
A1  - Cardenzana, J. V.
A1  - Cerruti, M.
A1  - Cesarini, A.
A1  - Chen, Xuhui
A1  - Ciupik, L.
A1  - Collins-Hughes, E.
A1  - Connolly, M. P.
A1  - Cui, W.
A1  - Dumm, J.
A1  - Eisch, J. D.
A1  - Falcone, A.
A1  - Federici, Simone
A1  - Feng, Q.
A1  - Finley, J. P.
A1  - Fleischhack, H.
A1  - Fortin, P.
A1  - Fortson, L.
A1  - Furniss, A.
A1  - Galante, N.
A1  - Gall, D.
A1  - Gillanders, G. H.
A1  - Griffin, S.
A1  - Griffiths, S. T.
A1  - Grube, J.
A1  - Gyuk, G.
A1  - Hütten, M.
A1  - Hakansson, Nils
A1  - Holder, J.
A1  - Hughes, G.
A1  - Humensky, T. B.
A1  - Johnson, C. A.
A1  - Kaaret, P.
A1  - Kar, P.
A1  - Kelley-Hoskins, N.
A1  - Kertzman, M.
A1  - Khassen, Y.
A1  - Kieda, D.
A1  - Krause, M.
A1  - Krawczynski, H.
A1  - Krennrich, F.
A1  - Lang, M. J.
A1  - Madhavan, A. S.
A1  - Maier, G.
A1  - McArthur, S.
A1  - McCann, A.
A1  - Meagher, K.
A1  - Millis, J.
A1  - Moriarty, P.
A1  - Mukherjee, R.
A1  - Nieto, D.
A1  - Ong, R. A.
A1  - Orr, M.
A1  - Otte, A. N.
A1  - Pandel, D.
A1  - Park, N.
A1  - Pelassa, V.
A1  - Perkins, J. S.
A1  - Pichel, A.
A1  - Pohl, Martin
A1  - Popkow, A.
A1  - Quinn, J.
A1  - Ragan, K.
A1  - Reyes, L. C.
A1  - Reynolds, P. T.
A1  - Roache, E.
A1  - Rousselle, J.
A1  - Rovero, A. C.
A1  - Saxon, D. B.
A1  - Sembroski, G. H.
A1  - Shahinyan, K.
A1  - Sheidaei, F.
A1  - Skole, C.
A1  - Smith, A. W.
A1  - Staszak, D.
A1  - Telezhinsky, Igor O.
A1  - Theiling, M.
A1  - Todd, N. W.
A1  - Tucci, J. V.
A1  - Tyler, J.
A1  - Varlotta, A.
A1  - Vassiliev, V. V.
A1  - Vincent, S.
A1  - Wakely, S. P.
A1  - Weiner, O. M.
A1  - Weinstein, A.
A1  - Welsing, R.
A1  - Wilhelm, Alina
A1  - Williams, D. A.
A1  - Zitzer, B.
A1  - Baring, M. G.
A1  - Gonzalez, J. Becerra
A1  - Cillis, A. N.
A1  - Horan, D.
A1  - Paneque, D.
T1  - Very high energy outburst of Markarian 501 in May 2009
JF  - Physical chemistry, chemical physics : a journal of European Chemical Societies
N2  - The very high energy (VHE; E > 100 GeV) blazar Markarian 501 was observed between April 17 and May 5 (MJD 54 938-54 956), 2009, as part of an extensive multiwavelength campaign from radio to VHE. Strong VHE yray activity was detected on May 1st with Whipple and VERITAS, when the flux (E > 400 GeV) increased to 10 times the preflare baseline flux (3.9 x 10(-11) ph cm(-2) s(-1)), reaching five times the flux of the Crab Nebula. This coincided with a decrease in the optical polarization and a rotation of the polarization angle by 15. This VHE flare showed a fast flux variation with an increase of a factor similar to 4 in 25 min, and a falling time of similar to 50 min. We present the observations of the quiescent state previous to the flare and of the high state after the flare, focusing on the flux and spectral variability from Whipple, VERITAS, Fermi-LAT, RXTE, and Swift combined with optical and radio data.
KW  - BL Lacertae objects: individual: Mrk 501
KW  - gamma rays: galaxies
Y1  - 2016
U6  - https://doi.org/10.1051/0004-6361/201628744
SN  - 1432-0746
VL  - 594
PB  - EDP Sciences
CY  - Les Ulis
ER  - 
TY  - JOUR
A1  - Aliu, E.
A1  - Archambault, S.
A1  - Archer, A.
A1  - Benbow, W.
A1  - Bird, R.
A1  - Biteau, Jonathan
A1  - Buchovecky, M.
A1  - Buckley, J. H.
A1  - Bugaev, V.
A1  - Byrum, K.
A1  - Cardenzana, J. V.
A1  - Cerruti, M.
A1  - Chen, Xuhui
A1  - Ciupik, L.
A1  - Connolly, M. P.
A1  - Cui, W.
A1  - Dickinson, H. J.
A1  - Eisch, J. D.
A1  - Falcone, A.
A1  - Feng, Q.
A1  - Finley, J. P.
A1  - Fleischhack, H.
A1  - Flinders, A.
A1  - Fortin, P.
A1  - Fortson, L.
A1  - Furniss, A.
A1  - Gillanders, G. H.
A1  - Griffin, S.
A1  - Grube, J.
A1  - Gyuk, G.
A1  - Huetten, M.
A1  - Hakansson, Nils
A1  - Holder, J.
A1  - Humensky, T. B.
A1  - Johnson, C. A.
A1  - Kaaret, P.
A1  - Kar, P.
A1  - Kelley-Hoskins, N.
A1  - Kertzman, M.
A1  - Kieda, D.
A1  - Krause, M.
A1  - Lang, M. J.
A1  - Loo, A.
A1  - Maier, G.
A1  - McArthur, S.
A1  - McCann, A.
A1  - Meagher, K.
A1  - Moriarty, P.
A1  - Mukherjee, R.
A1  - Nguyen, T.
A1  - Nieto, D.
A1  - Ong, R. A.
A1  - Otte, A. N.
A1  - Pandel, D.
A1  - Park, N.
A1  - Pelassa, V.
A1  - Petrashyk, A.
A1  - Pohl, M.
A1  - Popkow, A.
A1  - Pueschel, Elisa
A1  - Quinn, J.
A1  - Ragan, K.
A1  - Reynolds, P. T.
A1  - Richards, G. T.
A1  - Roache, E.
A1  - Rulten, C.
A1  - Santander, M.
A1  - Sembroski, G. H.
A1  - Shahinyan, K.
A1  - Smith, A. W.
A1  - Staszak, D.
A1  - Telezhinsky, Igor O.
A1  - Tucci, J. V.
A1  - Tyler, J.
A1  - Varlotta, A.
A1  - Vincent, S.
A1  - Wakely, S. P.
A1  - Weiner, O. M.
A1  - Weinstein, A.
A1  - Wilhelm, Alina
A1  - Williams, D. A.
A1  - Zitzer, B.
A1  - Chernyakova, M.
A1  - Roberts, M. S. E.
T1  - A SEARCH FOR VERY HIGH ENERGY GAMMA RAYS FROM THE MISSING LINK BINARY PULSAR J1023+0038 WITH VERITAS
JF  - The astrophysical journal : an international review of spectroscopy and astronomical physics
N2  - The binary millisecond radio pulsar PSR J1023+0038 exhibits many characteristics similar to the gamma-ray binary system PSR B1259-63/LS 2883, making it an ideal candidate for the study of high-energy nonthermal emission. It has been the subject of multiwavelength campaigns following the disappearance of the pulsed radio emission in 2013 June, which revealed the appearance of an accretion disk around the neutron star. We present the results of very high energy (VHE) gamma-ray observations carried out by the Very Energetic Radiation Imaging Telescope Array System before and after this change of state. Searches for steady and pulsed emission of both data sets yield no significant gamma-ray signal above 100 GeV, and upper limits are given for both a steady and pulsed gamma-ray flux. These upper limits are used to constrain the magnetic field strength in the shock region of the PSR J1023+0038 system. Assuming that VHE gamma rays are produced via an inverse Compton mechanism in the shock region, we constrain the shock magnetic field to be greater than similar to 2 G before the disappearance of the radio pulsar and greater than similar to 10 G afterward.
KW  - binaries: general
KW  - gamma rays: general
KW  - pulsars: general
KW  - pulsars: individual (PSR J1023+0038)
Y1  - 2016
U6  - https://doi.org/10.3847/0004-637X/831/2/193
SN  - 0004-637X
SN  - 1538-4357
VL  - 831
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - THES
A1  - Amaro-Seoane, Pau
T1  - Dense stellar systems and massive black holes
T1  - Dichte stellare Systeme und massive Schwarze Löcher
BT  - sources of gravitational radiation and tidal disruptions
BT  - Quellen von Gravitationsstrahlung und Gezeiten-Sternzerissereignissen
N2  - Gravity dictates the structure of the whole Universe and, although it is triumphantly described by the theory of General Relativity, it is the force that we least understand in nature. One of the cardinal predictions of this theory are black holes. Massive, dark objects are found in the majority of galaxies. Our own galactic center very contains such an object with a mass of about four million solar masses. Are these objects supermassive black holes (SMBHs), or do we need alternatives? The answer lies in the event horizon, the characteristic that defines a black hole. The key to probe the horizon is to model the movement of stars around a SMBH, and the interactions between them, and look for deviations from real observations. Nuclear star clusters harboring a massive, dark object with a mass of up to ~ ten million solar masses are good testbeds to probe the event horizon of the potential SMBH with stars. The channel for interactions between stars and the central MBH are the fact that (a) compact stars and stellar-mass black holes can gradually inspiral into the SMBH due to the emission of gravitational radiation, which is known as an “Extreme Mass Ratio Inspiral” (EMRI), and (b) stars can produce gases which will be accreted by the SMBH through normal stellar evolution, or by collisions and disruptions brought about by the strong central tidal field. Such processes can contribute significantly to the mass of the SMBH. These two processes involve different disciplines, which combined will provide us with detailed information about the fabric of space and time. In this habilitation I present nine articles of my recent work directly related with these topics.
N2  - Die Gravitation bestimmt die Struktur des ganzen Universums und ist, obwohl sie mit großem Erfolg durch die Theorie der Allgemeinen Relativitätstheorie beschrieben wird, die am wenigsten verstandene Kraft in der Natur. Eine der grundsätzlichsten Vorhersagen dieser Theorie sind Schwarze Löcher. Massive, dunkle Objekte befinden sich in einem Großteil aller Galaxien. Das Zentrum unserer eigenen Galaxis enthält solch ein Objekt mit einer Masse von etwa vier Millionen Sonnenmassen. Sind diese Objekte supermassive Schwarze Löcher oder brauchen wir Alternativen? Die Antwort liegt im Ereignishorizont, der Eigenschaft, die ein Schwarzes Loch definiert. Der Schlüssel um den Ereignishorizont zu untersuchen ist, die Bewegungen der Sterne um eine Supermassives Schwarzes Loch zu modellieren, sowie deren Interaktionen, und nach Abweichungen von unseren Erwartungen in echten Beobachtungen zu suchen. Zentrale Sternhaufen, die ein massives, dunkles Objekt mit einer Masse bis zu ∼ zehn Millionen Sonnenmassen enthalten, sind gute Laborarien um den Ereignishorizont eines möglichen supermassiven Schwarzen Lochs mit Hilfe von Sternen zu untersuchen. Die Kanäle für mögliche Wechselwirkungen zwischen Sternen und einem zentralen Schwarzen Loch sind: (a) Kompakte Sternreste und stellare Schwarze Löcher können durch die Emission von Gravitationswellen allmählich auf spiralförmigen Orbits in das supermassive Schwarze Loch fallen, was als “Extreme Mass Ratio Inspiral” (EMRI) bezeichent wird. (b) Durch normale Sternentwicklung (Sternwinde) sowie durch Sternkollisionen oder Zerstörung von Sternen im starken zentralen Gezeitenfeld kann Gas freigesetzt werden, welches anschließend vom supermassiven Schwarzen Loch akkretiert werden kann. Solche Prozesse können wesentlich zur Masse eines Supermassiven Schwarzen Lochs beitragen. Die beiden Prozesse (a und b) beinhalten verschiedene astrophysikalische Aspekte, welche uns in ihrer Kombination mit detaillierter Information über die Beschaffenheit der Raumzeit versorgen. In dieser Habilitationsschrift präsentiere ich neun Artikel aus meiner jüngeren Forschungsarbeit, welche direkt Probleme aus diesen Themenbereichen behandeln.
KW  - stellar dynamics
KW  - massive black holes
KW  - gravitational waves
KW  - general relativity
KW  - Stellardynamik
KW  - massive Schwarze Löcher
KW  - Gravitationswellen
KW  - allgemeine Relativitätstheorie
Y1  - 2016
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-95439
ER  - 
TY  - JOUR
A1  - Archambault, S.
A1  - Archer, A.
A1  - Aune, T.
A1  - Barnacka, Anna
A1  - Benbow, W.
A1  - Bird, R.
A1  - Buchovecky, M.
A1  - Buckley, J. H.
A1  - Bugaev, V.
A1  - Byrum, K.
A1  - Cardenzana, J. V.
A1  - Cerruti, M.
A1  - Chen, Xuhui
A1  - Ciupik, L.
A1  - Collins-Hughes, E.
A1  - Connolly, M. P.
A1  - Cui, W.
A1  - Dickinson, H. J.
A1  - Dumm, J.
A1  - Eisch, J. D.
A1  - Falcone, A.
A1  - Feng, Q.
A1  - Finley, J. P.
A1  - Fleischhack, H.
A1  - Flinders, A.
A1  - Fortin, P.
A1  - Fortson, L.
A1  - Furniss, A.
A1  - Gillanders, G. H.
A1  - Griffin, S.
A1  - Grube, J.
A1  - Gyuk, G.
A1  - Huetten, M.
A1  - Hakansson, Nils
A1  - Hanna, D.
A1  - Holder, J.
A1  - Humensky, T. B.
A1  - Johnson, C. A.
A1  - Kaaret, P.
A1  - Kar, P.
A1  - Kelley-Hoskins, N.
A1  - Kertzman, M.
A1  - Khassen, Y.
A1  - Kieda, D.
A1  - Krause, M.
A1  - Krennrich, F.
A1  - Kumar, S.
A1  - Lang, M. J.
A1  - Maier, G.
A1  - McArthur, S.
A1  - McCann, A.
A1  - Meagher, K.
A1  - Millis, J.
A1  - Moriarty, P.
A1  - Mukherjee, R.
A1  - Nieto, D.
A1  - Ong, R. A.
A1  - Otte, A. N.
A1  - Pandel, D.
A1  - Park, N.
A1  - Pelassa, V.
A1  - Pohl, Martin
A1  - Popkow, A.
A1  - Pueschel, Elisa
A1  - Quinn, J.
A1  - Ragan, K.
A1  - Reynolds, P. T.
A1  - Richards, G. T.
A1  - Roache, E.
A1  - Rousselle, J.
A1  - Rulten, C.
A1  - Santander, M.
A1  - Sembroski, G. H.
A1  - Shahinyan, K.
A1  - Smith, A. W.
A1  - Staszak, D.
A1  - Telezhinsky, Igor O.
A1  - Tucci, J. V.
A1  - Tyler, J.
A1  - Vincent, S.
A1  - Wakely, S. P.
A1  - Weiner, O. M.
A1  - Weinstein, A.
A1  - Wilhelm, Alina
A1  - Williams, D. A.
A1  - Zitzer, B.
T1  - EXCEPTIONALLY BRIGHT TEV FLARES FROM THE BINARY LS I+61 degrees 303
JF  - The astrophysical journal : an international review of spectroscopy and astronomical physics ; Part 2, Letters
N2  - The TeV binary system LS I +61 degrees 303 is known for its regular, non-thermal emission pattern that traces the orbital period of the compact object in its 26.5 day orbit around its B0 Ve star companion. The system typically presents elevated TeV emission around apastron passage with flux levels between 5% and 15% of the steady flux from the Crab Nebula (> 300 GeV). In this article, VERITAS observations of LS I + 61 degrees. 303 taken in late 2014 are presented, during which bright TeV flares around apastron at flux levels peaking above 30% of the Crab Nebula flux were detected. This is the brightest such activity from this source ever seen in the TeV regime. The strong outbursts have rise and fall times of less than a day. The short timescale of the flares, in conjunction with the observation of 10 TeV photons from LS I + 61 degrees 303 during the flares, provides constraints on the properties of the accelerator in the source.
KW  - binaries: general
KW  - gamma-rays: general
KW  - stars: individual (LS I+61 degrees 303, VER J0240+612)
KW  - X-rays: binaries
Y1  - 2016
U6  - https://doi.org/10.3847/2041-8205/817/1/L7
SN  - 2041-8205
SN  - 2041-8213
VL  - 817
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Archambault, S.
A1  - Archer, A.
A1  - Barnacka, Anna
A1  - Behera, B.
A1  - Beilicke, M.
A1  - Benbow, W.
A1  - Berger, K.
A1  - Bird, R.
A1  - Böttcher, Markus
A1  - Buckley, J. H.
A1  - Bugaev, V.
A1  - Cardenzana, J. V.
A1  - Cerruti, M.
A1  - Chen, Xuhui
A1  - Christiansen, J. L.
A1  - Ciupik, L.
A1  - Collins-Hughes, E.
A1  - Connolly, M. P.
A1  - Cui, W.
A1  - Dickinson, H. J.
A1  - Dumm, J.
A1  - Eisch, J. D.
A1  - Errando, M.
A1  - Falcone, A.
A1  - Federici, Simone
A1  - Feng, Q.
A1  - Finley, J. P.
A1  - Fleischhack, H.
A1  - Fortson, L.
A1  - Furniss, A.
A1  - Gillanders, G. H.
A1  - Godambe, S.
A1  - Griffin, S.
A1  - Griffiths, S. T.
A1  - Grube, J.
A1  - Gyuk, G.
A1  - Hakansson, Nils
A1  - Hanna, D.
A1  - Holder, J.
A1  - Hughes, G.
A1  - Johnson, C. A.
A1  - Kaaret, P.
A1  - Kar, P.
A1  - Kertzman, M.
A1  - Khassen, Y.
A1  - Kieda, D.
A1  - Krawczynski, H.
A1  - Kumar, S.
A1  - Lang, M. J.
A1  - Madhavan, A. S.
A1  - Maier, G.
A1  - McArthur, S.
A1  - McCann, A.
A1  - Meagher, K.
A1  - Millis, J.
A1  - Moriarty, P.
A1  - Nelson, T.
A1  - Nieto, D.
A1  - Ong, R. A.
A1  - Otte, A. N.
A1  - Park, N.
A1  - Perkins, J. S.
A1  - Pohl, Martin
A1  - Popkow, A.
A1  - Prokoph, H.
A1  - Pueschel, Elisa
A1  - Quinn, J.
A1  - Ragan, K.
A1  - Rajotte, J.
A1  - Reyes, L. C.
A1  - Reynolds, P. T.
A1  - Richards, G. T.
A1  - Roache, E.
A1  - Sembroski, G. H.
A1  - Shahinyan, K.
A1  - Smith, A. W.
A1  - Staszak, D.
A1  - Sweeney, K.
A1  - Telezhinsky, Igor O.
A1  - Tucci, J. V.
A1  - Tyler, J.
A1  - Varlotta, A.
A1  - Vassiliev, V. V.
A1  - Wakely, S. P.
A1  - Welsing, R.
A1  - Wilhelm, Alina
A1  - Williams, D. A.
A1  - Zitzer, B.
T1  - Discovery of very high energy gamma rays from 1ES 1440+122
JF  - Monthly notices of the Royal Astronomical Society
KW  - BL Lacertae objects: general
KW  - gamma-rays: general
Y1  - 2016
U6  - https://doi.org/10.1093/mnras/stw1319
SN  - 0035-8711
SN  - 1365-2966
VL  - 461
SP  - 202
EP  - 208
PB  - Oxford Univ. Press
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Archambault, S.
A1  - Archer, A.
A1  - Benbow, W.
A1  - Bird, R.
A1  - Biteau, Jonathan
A1  - Buchovecky, M.
A1  - Buckley, J. H.
A1  - Bugaev, V.
A1  - Byrum, K.
A1  - Cerruti, M.
A1  - Chen, Xuhui
A1  - Ciupik, L.
A1  - Connolly, M. P.
A1  - Cui, W.
A1  - Eisch, J. D.
A1  - Errando, M.
A1  - Falcone, A.
A1  - Feng, Q.
A1  - Finley, J. P.
A1  - Fleischhack, H.
A1  - Fortin, P.
A1  - Fortson, L.
A1  - Furniss, A.
A1  - Gillanders, G. H.
A1  - Griffin, S.
A1  - Grube, J.
A1  - Gyuk, G.
A1  - Huetten, M.
A1  - Hakansson, Nils
A1  - Hanna, D.
A1  - Holder, J.
A1  - Humensky, T. B.
A1  - Johnson, C. A.
A1  - Kaaret, P.
A1  - Kar, P.
A1  - Kelley-Hoskins, N.
A1  - Kertzman, M.
A1  - Kieda, D.
A1  - Krause, M.
A1  - Krennrich, F.
A1  - Kumar, S.
A1  - Lang, M. J.
A1  - Maier, G.
A1  - McArthur, S.
A1  - McCann, A.
A1  - Meagher, K.
A1  - Moriarty, P.
A1  - Mukherjee, R.
A1  - Nguyen, T.
A1  - Nieto, D.
A1  - Ong, R. A.
A1  - Otte, A. N.
A1  - Park, N.
A1  - Perkins, J. S.
A1  - Pichel, A.
A1  - Pohl, Martin
A1  - Popkow, A.
A1  - Pueschel, Elisa
A1  - Quinn, J.
A1  - Ragan, K.
A1  - Reynolds, P. T.
A1  - Richards, G. T.
A1  - Roache, E.
A1  - Rovero, A. C.
A1  - Santander, M.
A1  - Sembroski, G. H.
A1  - Shahinyan, K.
A1  - Smith, A. W.
A1  - Staszak, D.
A1  - Telezhinsky, Igor O.
A1  - Tucci, J. V.
A1  - Tyler, J.
A1  - Vincent, S.
A1  - Wakely, S. P.
A1  - Weiner, O. M.
A1  - Weinstein, A.
A1  - Williams, D. A.
A1  - Zitzer, B.
A1  - Fumagalli, M.
A1  - Prochaska, J. X.
T1  - UPPER LIMITS FROM FIVE YEARS OF BLAZAR OBSERVATIONS WITH THE VERITAS CHERENKOV TELESCOPES
JF  - The astronomical journal
N2  - Between the beginning of its full-scale scientific operations in 2007 and 2012, the VERITAS Cherenkov telescope array observed more than 130 blazars; of these, 26 were detected as very-high-energy (VHE; E > 100 GeV) gamma-ray sources. In this work, we present the analysis results of a sample of 114 undetected objects. The observations constitute a total live-time of similar to 570 hr. The sample includes several unidentified Fermi-Large Area Telescope (LAT) sources (located at high Galactic latitude) as well as all the sources from the second Fermi-LAT catalog that are contained within the field of view of the VERITAS observations. We have also performed optical spectroscopy measurements in order to estimate the redshift of some of these blazars that do not have spectroscopic distance estimates. We present new optical spectra from the Kast instrument on the Shane telescope at the Lick observatory for 18 blazars included in this work, which allowed for the successful measurement or constraint on the redshift of four of them. For each of the blazars included in our sample, we provide the flux upper limit in the VERITAS energy band. We also study the properties of the significance distributions and we present the result of a stacked analysis of the data set, which shows a 4s excess.
KW  - BL Lacertae objects: general
KW  - galaxies: active
KW  - gamma rays: galaxies
KW  - radiation mechanisms: non-thermal
Y1  - 2016
U6  - https://doi.org/10.3847/0004-6256/151/6/142
SN  - 0004-6256
SN  - 1538-3881
VL  - 151
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Archer, A.
A1  - Benbow, W.
A1  - Bird, R.
A1  - Buchovecky, M.
A1  - Buckley, J. H.
A1  - Bugaev, V.
A1  - Byrum, K.
A1  - Cardenzana, J. V.
A1  - Cerruti, M.
A1  - Chen, Xuhui
A1  - Ciupik, L.
A1  - Collins-Hughes, E.
A1  - Connolly, M. P.
A1  - Eisch, J. D.
A1  - Falcone, A.
A1  - Feng, Q.
A1  - Finley, J. P.
A1  - Fleischhack, H.
A1  - Flinders, A.
A1  - Fortson, L.
A1  - Furniss, A.
A1  - Gillanders, G. H.
A1  - Griffin, S.
A1  - Grube, J.
A1  - Gyuk, G.
A1  - Hakansson, Nils
A1  - Hanna, D.
A1  - Holder, J.
A1  - Humensky, T. B.
A1  - Huetten, M.
A1  - Johnson, C. A.
A1  - Kaaret, P.
A1  - Kar, P.
A1  - Kelley-Hoskins, N.
A1  - Kertzman, M.
A1  - Kieda, D.
A1  - Krause, M.
A1  - Krennrich, F.
A1  - Kumar, S.
A1  - Lang, M. J.
A1  - McArthur, S.
A1  - McCann, A.
A1  - Meagher, K.
A1  - Millis, J.
A1  - Moriarty, P.
A1  - Mukherjee, R.
A1  - Nieto, D.
A1  - Ong, R. A.
A1  - Park, N.
A1  - Pelassa, V.
A1  - Pohl, Martin
A1  - Popkow, A.
A1  - Pueschel, Elisa
A1  - Quinn, J.
A1  - Ragan, K.
A1  - Ratliff, G.
A1  - Reynolds, P. T.
A1  - Richards, G. T.
A1  - Roache, E.
A1  - Rousselle, J.
A1  - Santander, M.
A1  - Sembroski, G. H.
A1  - Shahinyan, K.
A1  - Smith, A. W.
A1  - Staszak, D.
A1  - Telezhinsky, Igor O.
A1  - Tucci, J. V.
A1  - Tyler, J.
A1  - Vassiliev, V. V.
A1  - Wakely, S. P.
A1  - Weiner, O. M.
A1  - Weinstein, A.
A1  - Wilhelm, Alina
A1  - Williams, D. A.
A1  - Zitzer, B.
A1  - Yusef-Zadeh, F.
T1  - TEV GAMMA-RAY OBSERVATIONS OF THE GALACTIC CENTER RIDGE BY VERITAS
JF  - The astrophysical journal : an international review of spectroscopy and astronomical physics
N2  - The Galactic Center ridge has been observed extensively in the past by both GeV and TeV gamma-ray instruments revealing a wealth of structure, including a diffuse component and the point sources G0.9+0.1 (a composite supernova remnant) and Sgr A* (believed to be associated with the supermassive black hole located at the center of our Galaxy). Previous very high energy (VHE) gamma-ray observations with the H.E.S.S.. experiment have also detected an extended TeV gamma-ray component along the Galactic plane in the >300 GeV gamma-ray regime. Here we report on observations of the Galactic Center ridge from 2010 to 2014 by the VERITAS telescope array in the >2 TeV energy range. From these observations we (1) provide improved measurements of the differential energy spectrum for Sgr A* in the >2 TeV gamma-ray regime, (2) provide a detection in the >2 TeV gamma-ray emission from the composite SNR G0.9+0.1 and an improved determination of its multi-TeV gamma-ray energy spectrum, and. (3) report on the detection of VER J1746-289, a localized enhancement of >2 TeV gamma-ray emission along the Galactic plane.
KW  - Galaxy: center
KW  - gamma rays: general
KW  - supernovae: individual (G0.9+0.1)
Y1  - 2016
U6  - https://doi.org/10.3847/0004-637X/821/2/129
SN  - 0004-637X
SN  - 1538-4357
VL  - 821
SP  - 162
EP  - 167
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Arlt, Rainer
A1  - Valliappan, Senthamizh Pavai
A1  - Schmiel, C.
A1  - Spada, F.
T1  - Sunspot positions, areas, and group tilt angles for 1611-1631 from observations by Christoph Scheiner
JF  - Mountain research and development
N2  - Methods. In most cases, the given orientation of the ecliptic is used to set up the heliographic coordinate system for the drawings. Positions and sizes are measured manually on screen. Very early drawings have no indication of their orientation. A rotational matching using common spots of adjacent days is used in some cases, while in other cases, the assumption that images were aligned with a zenith-horizon coordinate system appeared to be the most probable.
KW  - Sun: activity
KW  - sunspots
KW  - history and philosophy of astronomy
Y1  - 2016
U6  - https://doi.org/10.1051/0004-6361/201629000
SN  - 1432-0746
VL  - 595
PB  - EDP Sciences
CY  - Les Ulis
ER  - 
TY  - JOUR
A1  - Aseev, Nikita
A1  - Shprits, Yuri Y.
A1  - Drozdov, Alexander
A1  - Kellerman, Adam C.
T1  - Numerical applications of the advective-diffusive codes for the inner magnetosphere
JF  - Space Weather: The International Journal of Research and Applications
N2  - In this study we present analytical solutions for convection and diffusion equations. We gather here the analytical solutions for the one-dimensional convection equation, the two-dimensional convection problem, and the one- and two-dimensional diffusion equations. Using obtained analytical solutions, we test the four-dimensional Versatile Electron Radiation Belt code (the VERB-4D code), which solves the modified Fokker-Planck equation with additional convection terms. The ninth-order upwind numerical scheme for the one-dimensional convection equation shows much more accurate results than the results obtained with the third-order scheme. The universal limiter eliminates unphysical oscillations generated by high-order linear upwind schemes. Decrease in the space step leads to convergence of a numerical solution of the two-dimensional diffusion equation with mixed terms to the analytical solution. We compare the results of the third- and ninth-order schemes applied to magnetospheric convection modeling. The results show significant differences in electron fluxes near geostationary orbit when different numerical schemes are used.
KW  - advective-diffusive codes
KW  - inner magnetosphere
KW  - numerical schemes
Y1  - 2016
U6  - https://doi.org/10.1002/2016SW001484
SN  - 1542-7390
VL  - 14
SP  - 993
EP  - 1010
PB  - American Geophysical Union
CY  - Washington
ER  - 
TY  - THES
A1  - Ata, Metin
T1  - Phase-space reconstructions of cosmic velocities and the cosmic web
T1  - Phasenraumrekonstruktionen kosmischer Geschwindigkeiten und des kosmischen Netzes
BT  - structure formation models - galaxy bias models - galaxy redshift surveys - inference analysis
N2  - In the current paradigm of cosmology, the formation of large-scale structures is mainly driven by non-radiating dark matter, making up the dominant part of the matter budget of the Universe. Cosmological observations however, rely on the detection of luminous galaxies, which are biased tracers of the underlying dark matter. In this thesis I present cosmological reconstructions of both, the dark matter density field that forms the cosmic web, and cosmic velocities, for which both aspects of my work are delved into, the theoretical formalism and the results of its applications to cosmological simulations and also to a galaxy redshift survey.The foundation of our method is relying on a statistical approach, in which a given galaxy catalogue is interpreted as a biased realization of the underlying dark matter density field. The inference is computationally performed on a mesh grid by sampling from a probability density function, which describes the joint posterior distribution of matter density and the three dimensional velocity field. The statistical background of our method is described in Chapter ”Implementation of argo”, where the introduction in sampling methods is given, paying special attention to Markov Chain Monte-Carlo techniques. In Chapter ”Phase-Space Reconstructions with N-body  Simulations”, I introduce and implement a novel biasing scheme to relate the galaxy number density to the underlying dark matter, which I decompose into a deterministic part, described by a non-linear and scale-dependent analytic expression, and a stochastic part, by presenting a negative binomial (NB) likelihood function that models deviations from Poissonity. Both bias components had already been studied theoretically, but were so far never tested in a reconstruction algorithm. I test these new contributions againstN-body simulations to quantify improvements and show that, compared to state-of-the-art methods, the stochastic bias is inevitable at wave numbers of k≥0.15h Mpc^−1 in the power spectrum in order to obtain unbiased results from the reconstructions. In the second part of Chapter ”Phase-Space Reconstructions with N-body Simulations” I describe and validate our approach to infer the three dimensional cosmic velocity field jointly with the dark matter density. I use linear perturbation theory for the large-scale bulk flows and a dispersion term to model virialized galaxy motions, showing that our method is accurately recovering the real-space positions of the redshift-space distorted galaxies. I analyze the results with the isotropic and also the two-dimensional power spectrum.Finally, in Chapter ”Phase-space Reconstructions with Galaxy Redshift Surveys”, I show how I combine all findings and results and apply the method to the CMASS (for Constant (stellar) Mass) galaxy catalogue of the Baryon Oscillation Spectroscopic Survey (BOSS). I describe how our method is  accounting  for the observational selection effects inside our reconstruction algorithm. Also, I demonstrate that the renormalization of the prior distribution function is mandatory to account for higher order contributions in the structure formation model, and finally a redshift-dependent bias factor is theoretically motivated and implemented into our method. The various refinements yield unbiased results of the dark matter until scales of k≤0.2 h Mpc^−1in the power spectrum and isotropize the galaxy catalogue down to distances of r∼20h^−1 Mpc in the correlation function. We further test the  results of our cosmic velocity field reconstruction by comparing them to a synthetic mock galaxy catalogue, finding a strong correlation between the mock and the reconstructed  velocities. The applications of both, the density field without redshift-space distortions, and the velocity reconstructions, are very broad and can be used for improved analyses of the baryonic acoustic oscillations, environmental studies of the cosmic web, the kinematic Sunyaev-Zel’dovic or integrated Sachs-Wolfe effect.
N2  - In der gegenwärtigen Anschauung der Kosmologie wird die Bildung von großräumigen Strukturen vor allem durch nicht strahlende, Dunkle Materie beeinflusst, die den überwiegenden Teil des Materieanteils des Universums ausmacht. Kosmologische Beobachtungen beruhen jedoch auf dem Nachweis von leuchtenden Galaxien, die gebiaste Indikatoren (biased tracer) der darunterliegenden Dunklen Materie sind. In dieser Arbeit präsentiere ich Rekonstruktionen des kosmischen Netzes der Dunklen Materie und kosmischer Geschwindigkeitsfelder. Beide Aspekte meiner Arbeit, der theoretische Formalismus und die Ergebnisse der Anwendungen sowohl auf kosmologische Simulationen als auch auf Galaxie-Rotverschiebungssurveys, weden detaiiert aufgeführt. Die Grundlage dieser Methode beruht auf einem statistischen Ansatz, bei dem ein gegebener Galaxienkatalog als eine Realisierung des darunter liegenden Dunklen Materiedichtefeldes interpretiert wird. Unsere Rekonstruktionen werden rechnerisch auf einem Gitter durch das Sampling einer Wahrscheinlichkeitsdichtefunktion durchgeführt, die die gemeinsame a posteriori Wahrscheinlichkeit der Materiedichte und des dreidimensionalen Geschwindigkeitsfeldes beschreibt. Der statistische Hintergrund unserer Methode ist im Kapitel "Implantation of argo" beschrieben, wobei die Einführung in die Samplingmethoden unter besonderer Berücksichtigung der Markov-Kette-Monte-Carlo-Technik erfolgt. Im Kapitel "Phase-Space Reconstructions with N-body Simulations" stelle ich ein neuartiges Biasmodell vor, welches die Galaxienanzahldichte mit der darunter liegenden Dunklen Materiedichte verknüpft. Diesen zerlege ich in einen deterministischen, nicht linearen und skalenabhängigen analytischen Teil und einen stochastischen Teil. Das letztere beschreibe ich durch einen Negativ-Binomial-Likelihood Ausdruck, welches die Abweichungen von Poissonität modelliert. Beide Biaskomponenten wurden bereits theoretisch untersucht, aber bisher noch nie in einem Rekonstruktionsalgorithmus getestet. Ich evaluiere diese neuen Beiträge mit $N$-Körper-Simulationen, um die Verbesserungen zu beurteilen und um zu zeigen, dass der stochastische Bias im Leistungsspektrum bei Wellenzahlen von  k < 0.15 h Mpc^- 1 unabdingbar ist. Im zweiten Teil des Kapitels "Phase-Space Reconstructions with N-body Simulations" beschreibe und validiere ich unseren Ansatz, das kosmische Geschwindigkeitsfeld gemeinsam mit der Dunklen Materiedichte zu rekonstruieren. Ich verwende lineare Störungstheorie für die großräumigen Potentialströme und einen Dispersionsterm, um virialisierte Galaxiebewegungen zu modellieren. Die Ergebnisse zeigen, dass unsere Methode die Rotverschiebungsverzerrungen der Positionen der Galaxien genau beschreibt. Ich analysiere die Ergebnisse sowohl mit dem anisotropen Leistungsspektrum, als auch mit dem zweidimensionalen Leistungsspektrum. Schließlich zeige ich im Kapitel "Phase-space Reconstructions with Galaxy Redshift Surveys", wie ich alle Ergebnisse kombiniere und die Methode auf den CMASS (für Constant (stellar) Mass) Galaxienkatalog anwende. Ich beschreibe, wie unsere Methode die Selektionseffekte der Beobachtungen innerhalb des Rekonstruktionsalgorithmus berücksichtigt. Weiterhin demonstriere ich, dass die Renormalisierung der a priori Verteilung zwingend erforderlich ist, um die Beiträge höherer Ordnung im Strukturbildungsmodell zu berücksichtigen. Außerdem wird ein rotverschiebungsabhängiger Bias-Faktor theoretisch motiviert und in unseren Algorithmus implementiert. Unsere Rekonstruktionen, welche diese verschiedenen Verfeinerungen beinhaten, führen zu robusten Ergebnissen hinsichtlich des Feldes der Dunklen Materie bis zu Skalen von k <0.2 Mpc^-1 im Leistungsspektrum. Außerdem werden Anisotropien in dem rekonstruierten Galaxienkatalog bis zu Abständen von r~20  h^-1 Mpc in der Korrelationsfunktion zu einem hohen Grad überwunden. Wir testen die Ergebnisse unserer kosmischen Geschwindigkeitsrekonstruktion, indem wir sie mit einem synthetischen Mock-Galaxienkatalog vergleichen und bestätigen eine starke Korrelation zwischen den Mock- und den rekonstruierten Geschwindigkeiten. Die Anwendungen sowohl des Dichtefeldes ohne Rotverschiebungsverzerrungen als auch der Geschwindigkeitsrekonstruktionen sind sehr vielfältig und können für verbesserte Analysen der baryonischen akustischen Oszillationen, Umgebungsstudien des kosmischen Netzes, des kinematischen  Sunjajew-Seldowitsch-Effekts oder des integrierten Sachs-Wolfe-Effekts verwendet werden.
KW  - large-scale structure formation
KW  - großräumige Strukturen
KW  - Kosmologie
KW  - Theorie
KW  - cosmology
KW  - theory
Y1  - 2016
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-403565
ER  - 
TY  - JOUR
A1  - Balthasar, H.
A1  - Gömöry, P.
A1  - González Manrique, Sergio Javier
A1  - Kuckein, Christoph
A1  - Kavka, J.
A1  - Kucera, A.
A1  - Schwartz, P.
A1  - Vaskova, R.
A1  - Berkefeld, T.
A1  - Collados Vera, M.
A1  - Denker, Carsten
A1  - Feller, A.
A1  - Hofmann, A.
A1  - Lagg, A.
A1  - Nicklas, H.
A1  - Suarez, D.
A1  - Pastor Yabar, A.
A1  - Rezaei, R.
A1  - Schlichenmaier, R.
A1  - Schmidt, D.
A1  - Schmidt, W.
A1  - Sigwarth, M.
A1  - Sobotka, M.
A1  - Solanki, S. K.
A1  - Soltau, D.
A1  - Staude, J.
A1  - Strassmeier, Klaus G.
A1  - Volkmer, R.
A1  - von der Lühe, O.
A1  - Waldmann, T.
T1  - Spectropolarimetric observations of an arch filament system with the GREGOR solar telescope
JF  - Astronomische Nachrichten = Astronomical notes
N2  - Arch filament systems occur in active sunspot groups, where a fibril structure connects areas of opposite magnetic polarity, in contrast to active region filaments that follow the polarity inversion line. We used the GREGOR Infrared Spectrograph (GRIS) to obtain the full Stokes vector in the spectral lines SiI lambda 1082.7 nm, He I lambda 1083.0 nm, and Ca I lambda 1083.9 nm. We focus on the near-infrared calcium line to investigate the photospheric magnetic field and velocities, and use the line core intensities and velocities of the helium line to study the chromospheric plasma. The individual fibrils of the arch filament system connect the sunspot with patches of magnetic polarity opposite to that of the spot. These patches do not necessarily coincide with pores, where the magnetic field is strongest. Instead, areas are preferred not far from the polarity inversion line. These areas exhibit photospheric downflows of moderate velocity, but significantly higher downflows of up to 30 km s(-1) in the chromospheric helium line. Our findings can be explained with new emerging flux where the matter flows downward along the field lines of rising flux tubes, in agreement with earlier results. (C) 2016 WILEY-VCH Verlag GmbH& Co. KGaA, Weinheim
KW  - Sun: filaments
KW  - Sun: photosphere
KW  - techniques: polarimetric
KW  - techniques: spectroscopic
Y1  - 2016
U6  - https://doi.org/10.1002/asna.201612432
SN  - 0004-6337
SN  - 1521-3994
VL  - 337
SP  - 1050
EP  - 1056
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - GEN
A1  - Barniske, Andreas
A1  - Oskinova, Lida
A1  - Hamann, Wolf-Rainer
T1  - Two extremely luminous WN stars in the Galactic center with circumstellar emission from dust and gas (vol 486, pg 971, 2008)
T2  - Physical chemistry, chemical physics : a journal of European Chemical Societies
KW  - stars: Wolf-Rayet
KW  - HII regions
KW  - Galaxy: center
KW  - stars: individual: WR 102ka
KW  - stars: individual: WR 102c
KW  - errata, addenda
Y1  - 2016
U6  - https://doi.org/10.1051/0004-6361/200809568e
SN  - 1432-0746
VL  - 587
PB  - EDP Sciences
CY  - Les Ulis
ER  - 
TY  - GEN
A1  - Battiston, Stefano
A1  - Farmer, Doyne
A1  - Flache, Andreas
A1  - Garlaschelli, Diego
A1  - Haldane, Andy
A1  - Heesterbeek, Hans
A1  - Hommes, Cars
A1  - Jaeger, Carlo
A1  - May, Robert
A1  - Scheffer, Marten
T1  - Financial complexity: Accounting for fraud Response
T2  - Science
Y1  - 2016
U6  - https://doi.org/10.1126/science.352.6283.302
SN  - 0036-8075
SN  - 1095-9203
VL  - 352
SP  - 302
EP  - 302
PB  - American Assoc. for the Advancement of Science
CY  - Washington
ER  - 
TY  - GEN
A1  - Battiston, Stefano
A1  - Farmer, J. Doyne
A1  - Flache, Andreas
A1  - Garlaschelli, Diego
A1  - Haldane, Andrew G.
A1  - Heesterbeek, Hans
A1  - Hommes, Cars
A1  - Jaeger, Carlo
A1  - May, Robert
A1  - Scheffer, Marten
T1  - COMPLEX SYSTEMS Complexity theory and financial regulation
T2  - Science
N2  - Traditional economic theory could not explain, much less predict, the near collapse of the financial system and its long-lasting effects on the global economy. Since the 2008 crisis, there has been increasing interest in using ideas from complexity theory to make sense of economic and financial markets. Concepts, such as tipping points, networks, contagion, feedback, and resilience have entered the financial and regulatory lexicon, but actual use of complexity models and results remains at an early stage. Recent insights and techniques offer potential for better monitoring and management of highly interconnected economic and financial systems and, thus, may help anticipate and manage future crises.
Y1  - 2016
U6  - https://doi.org/10.1126/science.aad0299
SN  - 0036-8075
SN  - 1095-9203
VL  - 351
SP  - 818
EP  - 819
PB  - American Assoc. for the Advancement of Science
CY  - Washington
ER  - 
TY  - JOUR
A1  - Baushev, Anton N.
T1  - Can the dark matter annihilation signal be significantly boosted by substructures?
JF  - Journal of cosmology and astroparticle physics
N2  - A very general cosmological consideration suggests that, along with galactic dark matter halos, much smaller dark matter structures may exist. These structures are usually called `clumps', and their mass extends to 10&#8722;6 M &#8857; or even lower. The clumps should give the main contribution into the signal of dark matter annihilation, provided that they have survived until the present time. Recent observations favor a cored profile for low-mass astrophysical halos. We consider cored clumps and show that they are significantly less firm than the standard NFW ones. In contrast to the standard scenario, the cored clumps should have been completely destroyed inside ~ 20 kpc from the Milky Way center. The dwarf spheroidals should not contain any dark matter clumps. On the other hand, even under the most pessimistic assumption about the clump structure, the clumps should have survived in the Milky Way at a distance exceeding 50 kpc from the center, as well as in low-density cosmic structures. There they significantly boost the dark matter annihilation. We show that at least 70% of the clumps endured the primordial structure formation should still exist untouched in the present-day Universe.
KW  - dark matter theory
KW  - particle physics - cosmology connection
KW  - supersymmetry and cosmology
KW  - cosmic ray theory
Y1  - 2016
U6  - https://doi.org/10.1088/1475-7516/2016/01/018
SN  - 1475-7516
VL  - 30
SP  - 12
EP  - 18
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - THES
A1  - Bendre, Abhijit B.
T1  - Growth and saturation of dynamo in spiral galaxies via direct simulations
T1  - Wachstum und Sättigung des Dynamos in Spiralgalaxien mit direkten Simulationen
N2  - We do magnetohydrodynamic (MHD) simulations of local box models of turbulent Interstellar Medium (ISM) and analyse the process of amplification and saturation of mean magnetic fields with methods of mean field dynamo theory. It is shown that the process of saturation of mean fields can be partially described by the prolonged diffusion time scales in presence of the dynamically significant magnetic fields. However, the outward wind also plays an essential role in the saturation in higher SN rate case. Algebraic expressions for the back reaction of the magnetic field onto the turbulent transport coefficients are derived, which allow a complete description of the nonlinear dynamo. We also present the effects of dynamically significant mean fields on the ISM configuration and pressure distribution. We further add the cosmic ray component in the simulations and investigate the kinematic growth of mean fields with a dynamo perspective.
N2  - Wir fuehren magnetohydrodynamische (MHD) Simulationen des turbulenten interstellaren Mediums (ISM) in lokalen Boxen durch und analysieren darin den Prozess der Verstaerkung und Saturation der mittleren Magnetfelder mit Methoden der Dynamotheorie mittlerer Felder. Es wird gezeigt, dass der Prozess der Saturation mittlerer Felder teilweise durch eine verlaengerte Diffusionzeit in Gegenwart dynamisch signifikanter Magnetfelder erklaert werden kann. Fuer hoehere Supernovae-Raten spielt auch der nach aussen treibende Wind eine essenzielle Rolle fuer die Saturation. Aus den Simulationen konnten algebraische Formeln fuer die Rueckwirkung des Magnetfeldes auf die turbulenten Transportkoeffizienten abgeleitet werden, die eine vollstaendige Beschreibung des nichtlinearen Dynamos erlauben. Wir praesentieren zudem den Einfluss signifikanter mittlerer Magnetfelder auf die ISM-Konfiguration und Druckverteilung. Wir fuegen der Simulation ausserdem kosmische Strahlung als Komponente hinzu und untersuchen das kinematische Wachstum mittlerer Felder aus einer Dynamo-Perspektive.
KW  - magnetohydrodynamics
KW  - ISM: Turbulence
KW  - spiral galaxies: magnetic fields
KW  - nonliear dynamo
KW  - cosmic ray dynamo
KW  - Magnetohydrodynamik
KW  - ISM: Turbulenz
KW  - Spiralgalaxien: Magnetfelder
KW  - nichtlineare Dynamo
KW  - kosmische Strahlung Dynamo
Y1  - 2016
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-407517
ER  - 
TY  - GEN
A1  - Berenstein, Igal
A1  - Beta, Carsten
A1  - De Decker, Yannick
T1  - Comment on "Flow-induced arrest of spatiotemporal chaos and transition to a stationary pattern in the Gray-Scott model"
T2  - Physical review : E, Statistical, nonlinear and soft matter physics
N2  - In this Comment, we review the results of pattern formation in a reaction-diffusion-advection system following the kinetics of the Gray-Scott model. A recent paper by Das [Phys. Rev. E 92, 052914 (2015)] shows that spatiotemporal chaos of the intermittency type can disappear as the advective flow is increased. This study, however, refers to a single point in the space of kinetic parameters of the original Gray-Scott model. Here we show that the wealth of patterns increases substantially as some of these parameters are changed. In addition to spatiotemporal intermittency, defect-mediated turbulence can also be found. In all cases, however, the chaotic behavior is seen to disappear as the advective flow is increased, following a scenario similar to what was reported in our earlier work [I. Berenstein and C. Beta, Phys. Rev. E 86, 056205 (2012)] as well as by Das. We also point out that a similar phenomenon can be found in other reaction-diffusion-advection models, such as the Oregonator model for the Belousov-Zhabotinsky reaction under flow conditions.
Y1  - 2016
U6  - https://doi.org/10.1103/PhysRevE.94.046201
SN  - 2470-0045
SN  - 2470-0053
VL  - 94
PB  - American Physical Society
CY  - College Park
ER  - 
TY  - JOUR
A1  - Beta, Carsten
T1  - To turn or not to turn?
JF  - NEW JOURNAL OF PHYSICS
N2  - Bacteria typically swim in straight runs, interruped by sudden turning events. In particular, some species are limited to a reversal in the swimming direction as the only turning maneuver at their disposal. In a recent article, Grossmann et al (2016 New J. Phys. 18 043009) introduce a theoretical framework to analyze the diffusive properties of active particles following this type of run-and-reverse pattern. Based on a stochastic clock model to mimic the regulatory pathway that triggers reversal events, they show that a run-and-reverse swimmer can optimize its diffusive spreading by tuning the reversal rate according to the level of rotational noise. With their approach, they open up promising new perspectives of how to incorporate the dynamics of intracellular signaling into coarse-grained active particle descriptions.
KW  - bacterial swimming
KW  - random walks
KW  - diffusion
KW  - stochastic models
Y1  - 2016
U6  - https://doi.org/10.1088/1367-2630/18/5/051003
SN  - 1367-2630
VL  - 18
SP  - 1
EP  - 17
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Beye, Martin
A1  - Öberg, Henrik
A1  - Xin, Hongliang
A1  - Dakovski, Georgi L.
A1  - Föhlisch, Alexander
A1  - Gladh, Jorgen
A1  - Hantschmann, Markus
A1  - Hieke, Florian
A1  - Kaya, Sarp
A1  - Kühn, Danilo
A1  - LaRue, Jerry
A1  - Mercurio, Giuseppe
A1  - Minitti, Michael P.
A1  - Mitra, Ankush
A1  - Moeller, Stefan P.
A1  - Ng, May Ling
A1  - Nilsson, Anders
A1  - Nordlund, Dennis
A1  - Norskov, Jens
A1  - Öström, Henrik
A1  - Ogasawara, Hirohito
A1  - Persson, Mats
A1  - Schlotter, William F.
A1  - Sellberg, Jonas A.
A1  - Wolf, Martin
A1  - Abild-Pedersen, Frank
A1  - Pettersson, Lars G. M.
A1  - Wurth, Wilfried
T1  - Chemical Bond Activation Observed with an X-ray Laser
JF  - The journal of physical chemistry letters
N2  - The concept of bonding and antibonding orbitals is fundamental in chemistry. The population of those orbitals and the energetic difference between the two reflect the strength of the bonding interaction. Weakening the bond is expected to reduce this energetic splitting, but the transient character of bond-activation has so far prohibited direct experimental access. Here we apply time-resolved soft X-ray spectroscopy at a free electron laser to directly observe the decreased bonding antibonding splitting following bond-activation using an ultrashort optical laser pulse.
Y1  - 2016
U6  - https://doi.org/10.1021/acs.jpclett.6b01543
SN  - 1948-7185
VL  - 7
SP  - 3647
EP  - 3651
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - GEN
A1  - Bodrova, Anna S.
A1  - Chechkin, Aleksei V.
A1  - Cherstvy, Andrey G.
A1  - Safdari, Hadiseh
A1  - Sokolov, Igor M.
A1  - Metzler, Ralf
T1  - Underdamped scaled Brownian motion
BT  - (non-)existence of the overdamped limit in anomalous diffusion
N2  - It is quite generally assumed that the overdamped Langevin equation provides a quantitative description of the dynamics of a classical Brownian particle in the long time limit. We establish and investigate a paradigm anomalous diffusion process governed by an underdamped Langevin equation with an explicit time dependence of the system temperature and thus the diffusion and damping coefficients. We show that for this underdamped scaled Brownian motion (UDSBM) the overdamped limit fails to describe the long time behaviour of the system and may practically even not exist at all for a certain range of the parameter values. Thus persistent inertial effects play a non-negligible role even at significantly long times. From this study a general questions on the applicability of the overdamped limit to describe the long time motion of an anomalously diffusing particle arises, with profound consequences for the relevance of overdamped anomalous diffusion models. We elucidate our results in view of analytical and simulations results for the anomalous diffusion of particles in free cooling granular gases.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 267 
Y1  - 2016
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-97158
ER  - 
TY  - JOUR
A1  - Bodrova, Anna S.
A1  - Chechkin, Aleksei V.
A1  - Cherstvy, Andrey G.
A1  - Safdari, Hadiseh
A1  - Sokolov, Igor M.
A1  - Metzler, Ralf
T1  - Underdamped scaled Brownian motion
BT  - (non-)existence of the overdamped limit in anomalous diffusion
JF  - Scientific reports
N2  - It is quite generally assumed that the overdamped Langevin equation provides a quantitative description of the dynamics of a classical Brownian particle in the long time limit. We establish and investigate a paradigm anomalous diffusion process governed by an underdamped Langevin equation with an explicit time dependence of the system temperature and thus the diffusion and damping coefficients. We show that for this underdamped scaled Brownian motion (UDSBM) the overdamped limit fails to describe the long time behaviour of the system and may practically even not exist at all for a certain range of the parameter values. Thus persistent inertial effects play a non-negligible role even at significantly long times. From this study a general questions on the applicability of the overdamped limit to describe the long time motion of an anomalously diffusing particle arises, with profound consequences for the relevance of overdamped anomalous diffusion models. We elucidate our results in view of analytical and simulations results for the anomalous diffusion of particles in free cooling granular gases.
Y1  - 2016
U6  - https://doi.org/10.1038/srep30520
SN  - 2045-2322
VL  - 6
PB  - Nature Publishing Group
CY  - London
ER  - 
TY  - JOUR
A1  - Bodrova, Anna S.
A1  - Chechkin, Aleksei V.
A1  - Cherstvy, Andrey G.
A1  - Safdari, Hadiseh
A1  - Sokolov, Igor M.
A1  - Metzler, Ralf
T1  - Underdamped scaled Brownian motion: (non-)existence of the overdamped limit in anomalous diffusion
JF  - Scientific reports
N2  - It is quite generally assumed that the overdamped Langevin equation provides a quantitative description of the dynamics of a classical Brownian particle in the long time limit. We establish and investigate a paradigm anomalous diffusion process governed by an underdamped Langevin equation with an explicit time dependence of the system temperature and thus the diffusion and damping coefficients. We show that for this underdamped scaled Brownian motion (UDSBM) the overdamped limit fails to describe the long time behaviour of the system and may practically even not exist at all for a certain range of the parameter values. Thus persistent inertial effects play a non-negligible role even at significantly long times. From this study a general questions on the applicability of the overdamped limit to describe the long time motion of an anomalously diffusing particle arises, with profound consequences for the relevance of overdamped anomalous diffusion models. We elucidate our results in view of analytical and simulations results for the anomalous diffusion of particles in free cooling granular gases.
Y1  - 2016
U6  - https://doi.org/10.1038/srep30520
SN  - 2045-2322
VL  - 6
PB  - Nature Publ. Group
CY  - London
ER  - 
TY  - THES
A1  - Bojahr, Andre
T1  - Hypersound interaction studied by time-resolved inelastic light and x-ray scattering
T1  - Wechselwirkende Hyperschallwellen untersucht mittels zeitaufgelöster inelastischer Licht- und Röntgenstreuung
N2  - This publications-based thesis summarizes my contribution to the scientific field of ultrafast structural dynamics. It consists of 16 publications, about the generation, detection and coupling of coherent gigahertz longitudinal acoustic phonons, also called hypersonic waves. To generate such high frequency phonons, femtosecond near infrared laser pulses were used to heat nanostructures composed of perovskite oxides on an ultrashort timescale. As a consequence the heated regions of such a nanostructure expand and a high frequency acoustic phonon pulse is generated. To detect such coherent acoustic sound pulses I use ultrafast variants of optical Brillouin and x-ray scattering. Here an incident optical or x-ray photon is scattered by the excited sound wave in the sample. The scattered light intensity measures the occupation of the phonon modes. 
The central part of this work is the investigation of coherent high amplitude phonon wave packets which can behave nonlinearly, quite similar to shallow water waves which show a steepening of wave fronts or solitons well known as tsunamis. Due to the high amplitude of the acoustic wave packets in the solid, the acoustic properties can change significantly in the vicinity of the sound pulse. This may lead to a shape change of the pulse. I have observed by time-resolved Brillouin scattering, that a single cycle hypersound pulse shows a wavefront steepening. I excited hypersound pulses with strain amplitudes until 1% which I have calibrated by ultrafast x-ray diffraction (UXRD).
On the basis of this first experiment we developed the idea of the nonlinear mixing of narrowband phonon wave packets which we call "nonlinear phononics" in analogy with the nonlinear optics, which summarizes a kaleidoscope of surprising optical phenomena showing up at very high electric fields. Such phenomena are for instance Second Harmonic Generation, four-wave-mixing or solitons. But in case of excited coherent phonons the wave packets have usually very broad spectra which make it nearly impossible to look at elementary scattering processes between phonons with certain momentum and energy.
For that purpose I tested different techniques to excite narrowband phonon wave packets which mainly consist of phonons with a certain momentum and frequency. To this end epitaxially grown metal films on a dielectric substrate were excited with a train of laser pulses. These excitation pulses drive the metal film to oscillate with the frequency given by their inverse temporal displacement and send a hypersonic wave of this frequency into the substrate. The monochromaticity of these wave packets was proven by ultrafast optical Brillouin and x-ray scattering.
Using the excitation of such narrowband phonon wave packets I was able to observe the Second Harmonic Generation (SHG) of coherent phonons as a first example of nonlinear wave mixing of nanometric phonon wave packets.
N2  - Diese publikationsbasierte Dissertation fasst meinen Beitrag zum Forschungsgebiet der ultraschnellen Strukturdynamik zusammen.
Diese Arbeit besteht aus 16 Publikationen aus den Bereichen der Erzeugung, Detektion und Kopplung von kohärenten Gigahertz longitudinal-akustischen Phononen, auch Hyperschallwellen genannt. Um solch hochfrequente Phononen zu erzeugen, werden Femtosekunden nahinfrarot Laserpulse benutzt, um Nanostrukturen auf einer ultraschnellen Zeitskala zu erhitzen. Die aufgeheizten Regionen der Nanostruktur dehnen sich aufgrund der hohen Temperatur aus und ein hochfrequenter Schallpuls wird generiert. Um solche akustischen Pulse zu detektieren benutze ich ultraschnelle Varianten der Brillouin- und Röntgenstreuung. Dabei wird ein einfallendes optisches oder Röntgenphoton an der erzeugten Schallwelle gestreut. Die gemessene Streuintensität ist hierbei ein Maß für die Besetzung einzelner Phononenzustände.
Der zentrale Teil dieser Arbeit ist die Untersuchung von kohärenten Phonon-Wellenpaketen mit sehr hoher Amplitude. Diese Wellenpakete können sich nichtlinear verhalten, sehr ähnlich zu Flachwasserwellen bei denen nichtlineare Effekte in Form eines Aufsteilens der Wellenfronten oder der Existenz von Solitonen, bekannt als Tsunamis, äußern. Durch die hohe Amplitude der akustischen Wellenpakete können sich die akustischen Eigenschaften des Festkörpers in der Umgebung des Schallpulses signifikant ändern, welches sich dann in einer Formänderung des Schallpulses widerspiegelt. Ich konnte mittels zeitaufgelöster Brillouinstreuung das Aufsteilen der Wellenfronten eines Hyperschallpulses bestehend aus einem einzigen Oszillationszyklus beobachten. Hierbei wurden Hyperschallwellen mit einer Dehnungsamplitude von bis zu 1% angeregt, wobei ich diesen Wert mittels ultraschneller Röntgenbeugung kalibrieren konnte.
Mit diesem ersten Experiment als Basis entwickelten wir die Idee der nichtlinearen Wellenmischung von schmalbandigen Phonon-Wellenpaketen unter dem Titel "nichtlineare Phononik" in Analogie zur nichtlinearen Optik, welche sich aus einer Reihe von verblüffenden optischen Phänomenen bei sehr hohen elektrischen Feldstärken zusammensetzt. Solche Phänomene sind z. B. die optische Frequenzverdopplung, das Vier-Wellen-Mischen oder Solitone. Nur sind im Falle von kohärenten Phononen die erzeugten Spektren sehr breitbandig, was die Untersuchung von spezifischen Phononen mit festem Impuls und definierter Frequenz fast unmöglich macht.
Aus diesem Grund testete ich verschiedene Methoden um schmalbandige Phonon-Wellenpakete anzuregen, welche im Wesentlichen aus Phononen bestimmten Impulses und definierter Frequenz bestehen. Dafür wurden schließ lich epitaktisch auf ein dielektrisches Substrat aufgewachsene Metallfilme mit einen Laserpulszug angeregt. Hier sorgen die Lichtpulse für eine periodische Oszillation des Metalfilms, wobei die Anregefrequenz durch den inversen zeitlichen Abstand der Lichtpulse gegeben ist. Diese periodische Oszillation sendet dann ein Hyperschallwellenpaket eben dieser Frequenz ins Substrat. Die Monochromie dieser Wellenpakete konnte dabei mittels ultraschneller Brillouin- und Röntgenstreuung bestätigt werden.
Durch die Benutzung dieser schmalbandigen Phonon-Wellenpakete war es mir möglich, die Frequenzverdopplung (SHG) von kohärenten Phononen zu beobachten, was ein erstes Beispiel für die nichtlineare Wellenmischung von nanometrischen Phonon-Wellenpaketen ist.
KW  - hypersound
KW  - nonlinear acoustics
KW  - ultrafast
KW  - Brillouin scattering
KW  - x-ray diffraction
KW  - self-steepening
KW  - second-harmonic generation
KW  - Phononen
KW  - Wechselwirkung
KW  - Anharmonizität
KW  - nichtlineare Wellenmischung
KW  - zweite Harmonische
KW  - Phononenstreuung
KW  - nichlineare Phononik
Y1  - 2016
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-93860
ER  - 
TY  - JOUR
A1  - Bolotov, M. I.
A1  - Osipov, Grigory V.
A1  - Pikovskij, Arkadij
T1  - Marginal chimera state at cross-frequency locking of pulse-coupled neural networks
JF  - Physical review : E, Statistical, nonlinear and soft matter physics
N2  - We consider two coupled populations of leaky integrate-and-fire neurons. Depending on the coupling strength, mean fields generated by these populations can have incommensurate frequencies or become frequency locked. In the observed 2:1 locking state of the mean fields, individual neurons in one population are asynchronous with the mean fields, while in another population they have the same frequency as the mean field. These synchronous neurons form a chimera state, where part of them build a fully synchronized cluster, while other remain scattered. We explain this chimera as a marginal one, caused by a self-organized neutral dynamics of the effective circle map.
Y1  - 2016
U6  - https://doi.org/10.1103/PhysRevE.93.032202
SN  - 2470-0045
SN  - 2470-0053
VL  - 93
PB  - American Physical Society
CY  - College Park
ER  - 
TY  - JOUR
A1  - Bouche, Nicolas
A1  - Finley, H.
A1  - Schroetter, I.
A1  - Murphy, M. T.
A1  - Richter, Philipp
A1  - Bacon, Roland
A1  - Contini, Thierry
A1  - Richard, J.
A1  - Wendt, Martin
A1  - Kamann, S.
A1  - Epinat, Benoit
A1  - Cantalupo, Sebastiano
A1  - Straka, Lorrie A.
A1  - Schaye, Joop
A1  - Martin, C. L.
A1  - Peroux, C.
A1  - Wisotzki, Lutz
A1  - Soto, K.
A1  - Lilly, S.
A1  - Carollo, C. M.
A1  - Brinchmann, Jarle
A1  - Kollatschny, W.
T1  - POSSIBLE SIGNATURES OF A COLD-FLOW DISK FROM MUSE USING A z similar to 1
GALAXY-QUASAR PAIR TOWARD SDSS J1422-0001
JF  - The astrophysical journal : an international review of spectroscopy and astronomical physics
N2  - We use a background quasar to detect the presence of circumgalactic gas around a z = 0.91 low-mass star-forming galaxy. Data from the new Multi Unit Spectroscopic Explorer (MUSE) on the Very Large Telescope show that the galaxy has a dust-corrected star formation rate (SFR) of 4.7 +/- 2.0. M-circle dot yr(-1), with no companion down to 0.22 M-circle dot yr(-1) (5 sigma) within 240 h(-1) kpc ("30"). Using a high-resolution spectrum of the background quasar, which is fortuitously aligned with the galaxy major axis (with an azimuth angle alpha of only 15 degrees), we find, in the gas kinematics traced by low-ionization lines, distinct signatures consistent with those expected for a "cold-flow disk" extending at least 12 kpc (3 x R-1/2). We estimate the mass accretion rate M-in to be at least two to three times larger than the SFR, using the geometric constraints from the IFU data and the H (I) column density of log N-H (I)/cm(-2) similar or equal to 20.4 obtained from a Hubble Space Telescope/COS near-UV spectrum. From a detailed analysis of the low-ionization lines (e.g., Zn II, Cr II, Ti II, MnII, Si II), the accreting material appears to be enriched to about 0.4 Z(circle dot) (albeit with large uncertainties: log Z/Z(circle dot) = -0.4 +/- 0.4), which is comparable to the galaxy metallicity (12 + log O/H = 8.7 +/- 0.2), implying a large recycling fraction from past outflows. Blueshifted Mg II and Fe II absorptions in the galaxy spectrum from the MUSE data reveal the presence of an outflow. The Mg II and Fe II absorption line ratios indicate emission infilling due to scattering processes, but the MUSE data do not show any signs of fluorescent Fe II* emission.
KW  - galaxies: evolution
KW  - galaxies: formation
KW  - intergalactic medium
KW  - quasars: individual (SDSS J142253.31-000149)
Y1  - 2016
U6  - https://doi.org/10.3847/0004-637X/820/2/121
SN  - 0004-637X
SN  - 1538-4357
VL  - 820
SP  - 1872
EP  - 1882
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Boyd, A. J.
A1  - Spence, Harlan E.
A1  - Huang, Chia-Lin
A1  - Reeves, Geoffrey D.
A1  - Baker, Daniel N.
A1  - Turner, D. L.
A1  - Claudepierre, Seth G.
A1  - Fennell, Joseph F.
A1  - Blake, J. Bernard
A1  - Shprits, Yuri Y.
T1  - Statistical properties of the radiation belt seed population
JF  - Journal of geophysical research : Space physics
N2  - We present a statistical analysis of phase space density data from the first 26 months of the Van Allen Probes mission. In particular, we investigate the relationship between the tens and hundreds of keV seed electrons and >1 MeV core radiation belt electron population. Using a cross-correlation analysis, we find that the seed and core populations are well correlated with a coefficient of approximate to 0.73 with a time lag of 10-15 h. We present evidence of a seed population threshold that is necessary for subsequent acceleration. The depth of penetration of the seed population determines the inner boundary of the acceleration process. However, we show that an enhanced seed population alone is not enough to produce acceleration in the higher energies, implying that the seed population of hundreds of keV electrons is only one of several conditions required for MeV electron radiation belt acceleration.
Y1  - 2016
U6  - https://doi.org/10.1002/2016JA022652
SN  - 2169-9380
SN  - 2169-9402
VL  - 121
SP  - 7636
EP  - 7646
PB  - American Geophysical Union
CY  - Washington
ER  - 
TY  - JOUR
A1  - Bozzo, Enrico
A1  - Bhalerao, V.
A1  - Pradhan, Prajal
A1  - Tomsick, J.
A1  - Romano, Patrizia
A1  - Ferrigno, Carlo
A1  - Chaty, S.
A1  - Oskinova, Lida
A1  - Manousakis, A.
A1  - Walter, R.
A1  - Falanga, M.
A1  - Campana, S.
A1  - Stella, L.
A1  - Ramolla, M.
A1  - Chini, R.
T1  - Multi-wavelength observations of IGR J17544-2619 from quiescence to outburst
JF  - Journal of geophysical research : Earth surface
N2  - In this paper we report on a long multi-wavelength observational campaign of the supergiant fast X-ray transient prototype IGR J17544-2619. A 150 ks-long observation was carried out simultaneously with XMM-Newton and NuSTAR, catching the source in an initial faint X-ray state and then undergoing a bright X-ray outburst lasting approximately 7 ks. We studied the spectral variability during outburst and quiescence by using a thermal and bulk Comptonization model that is typically adopted to describe the X-ray spectral energy distribution of young pulsars in high mass X-ray binaries. Although the statistics of the collected X-ray data were relatively high, we could neither confirm the presence of a cyclotron line in the broad-band spectrum of the source (0.5-40 keV), nor detect any of the previously reported tentative detections of the source spin period. The monitoring carried out with Swift/XRT during the same orbit of the system observed by XMM-Newton and NuSTAR revealed that the source remained in a low emission state for most of the time, in agreement with the known property of all supergiant fast X-ray transients being significantly sub-luminous compared to other supergiant X-ray binaries. Optical and infrared observations were carried out for a total of a few thousand seconds during the quiescence state of the source detected by XMM-Newton and NuSTAR. The measured optical and infrared magnitudes were slightly lower than previous values reported in the literature, but compatible with the known micro-variability of supergiant stars. UV observations obtained with the UVOT telescope on-board Swift did not reveal significant changes in the magnitude of the source in this energy domain compared to previously reported values.
KW  - X-rays: binaries
Y1  - 2016
U6  - https://doi.org/10.1051/0004-6361/201629311
SN  - 1432-0746
VL  - 596
PB  - EDP Sciences
CY  - Les Ulis
ER  - 
TY  - JOUR
A1  - Bozzo, Enrico
A1  - Oskinova, Lida
A1  - Feldmeier, Achim
A1  - Falanga, M.
T1  - Clumpy wind accretion in supergiant neutron star high mass X-ray binaries
JF  - BMC neuroscience
N2  - The accretion of the stellar wind material by a compact object represents the main mechanism powering the X-ray emission in classical supergiant high mass X-ray binaries and supergiant fast X-ray transients. In this work we present the first attempt to simulate the accretion process of a fast and dense massive star wind onto a neutron star, taking into account the effects of the centrifugal and magnetic inhibition of accretion ("gating") due to the spin and magnetic field of the compact object. We made use of a radiative hydrodynamical code to model the nonstationary radiatively driven wind of an O-B supergiant star and then place a neutron star characterized by a fixed magnetic field and spin period at a certain distance from the massive companion. Our calculations follow, as a function of time (on a total timescale of several hours), the transitions of the system through all different accretion regimes that are triggered by the intrinsic variations in the density and velocity of the nonstationary wind. The X-ray luminosity released by the system is computed at each time step by taking into account the relevant physical processes occurring in the different accretion regimes. Synthetic lightcurves are derived and qualitatively compared with those observed from classical supergiant high mass X-ray binaries and supergiant fast X-ray transients. Although a number of simplifications are assumed in these calculations, we show that taking into account the effects of the centrifugal and magnetic inhibition of accretion significantly reduces the average X-ray luminosity expected for any neutron star wind-fed binary. The present model calculations suggest that long spin periods and stronger magnetic fields are favored in order to reproduce the peculiar behavior of supergiant fast X-ray transients in the X-ray domain.
KW  - stars: neutron
KW  - X-rays: binaries
KW  - supergiants
Y1  - 2016
U6  - https://doi.org/10.1051/0004-6361/201628341
SN  - 1432-0746
VL  - 589
SP  - 369
EP  - 389
PB  - EDP Sciences
CY  - Les Ulis
ER  - 
TY  - THES
A1  - Brauer, Dorothée
T1  - Chemo-kinematic constraints on Milky Way models from the spectroscopic surveys SEGUE & RAVE
T1  - Beschränkungen von Modellen der Milchstraße auf Basis der chemisch-kinematischen Analyse von Beobachtungsdaten der spektroskopischen Himmelsdurchmusterungen SEGUE und RAVE
N2  - The Milky Way is only one out of billions of galaxies in the universe. However, it is a special galaxy because it allows to explore the main mechanisms involved in its evolution and formation history by unpicking the system star-by-star. Especially, the chemical fingerprints of its stars provide clues and evidence of past events in the Galaxy’s lifetime. These information help not only to decipher the current structure and building blocks of the Milky Way, but to learn more about the general formation process of galaxies.

In the past decade a multitude of stellar spectroscopic Galactic surveys have scanned millions of stars far beyond the rim of the solar neighbourhood. The obtained spectroscopic information provide unprecedented insights to the chemo-dynamics of the Milky Way. In addition analytic models and numerical simulations of the Milky Way provide necessary descriptions and predictions suited for comparison with observations in order to decode the physical properties that underlie the complex system of the Galaxy.

In the thesis various approaches are taken to connect modern theoretical modelling of galaxy formation and evolution with observations from Galactic stellar surveys. With its focus on the chemo-kinematics of the Galactic disk this work aims to determine new observational constraints on the formation of the Milky Way providing also proper comparisons with two different models. These are the population synthesis model TRILEGAL based on analytical distribution functions, which aims to simulate the number and distribution of stars in the Milky Way and its different components, and a hybrid model (MCM) that combines an N-body simulation of a Milky Way like galaxy in the cosmological framework with a semi-analytic chemical evolution model for the Milky Way. The major observational data sets in use come from two surveys, namely the “Radial Velocity Experiment” (RAVE) and the “Sloan Extension for Galactic Understanding and Exploration” (SEGUE).

In the first approach the chemo-kinematic properties of the thin and thick disk of the Galaxy as traced by a selection of about 20000 SEGUE G-dwarf stars are directly compared to the predictions by the MCM model. As a necessary condition for this, SEGUE's selection function and its survey volume are evaluated in detail to correct the spectroscopic observations for their survey specific selection biases. Also, based on a Bayesian method spectro-photometric distances with uncertainties below 15% are computed for the selection of SEGUE G-dwarfs that are studied up to a distance of 3 kpc from the Sun.

For the second approach two synthetic versions of the SEGUE survey are generated based on the above models. The obtained synthetic stellar catalogues are then used to create mock samples best resembling the compiled sample of observed SEGUE G-dwarfs. Generally, mock samples are not only ideal to compare predictions from various models. They also allow validation of the models' quality and improvement as with this work could be especially achieved for TRILEGAL. While TRILEGAL reproduces the statistical properties of the thin and thick disk as seen in the observations, the MCM model has shown to be more suitable in reproducing many chemo-kinematic correlations as revealed by the SEGUE stars. However, evidence has been found that the MCM model may be missing a stellar component with the properties of the thick disk that the observations clearly show. While the SEGUE stars do indicate a thin-thick dichotomy of the stellar Galactic disk in agreement with other spectroscopic stellar studies, no sign for a distinct metal-poor disk is seen in the MCM model.

Usually stellar spectroscopic surveys are limited to a certain volume around the Sun covering different regions of the Galaxy’s disk. This often prevents to obtain a global view on the chemo-dynamics of the Galactic disk. Hence, a suitable combination of stellar samples from independent surveys is not only useful for the verification of results but it also helps to complete the picture of the Milky Way. Therefore, the thesis closes with a comparison of the SEGUE G-dwarfs and a sample of RAVE giants. The comparison reveals that the chemo-kinematic relations agree in disk regions where the samples of both surveys show a similar number of stars. For those parts of the survey volumes where one of the surveys lacks statistics they beautifully complement each other. This demonstrates that the comparison of theoretical models on the one side, and the combined observational data gathered by multiple surveys on the other side, are key ingredients to understand and disentangle the structure and formation history of the Milky Way.
N2  - Die Milchstraße ist nur eine unter Milliarden von Galaxien im Universum, dennoch ist sie besonders. Sie bietet die einzigartige Möglichkeit anhand ihrer einzeln auflösbaren Sterne und deren im Detail beobachtbaren Eigenschaften die Mechanismen ihrer Evolutions- und Entstehungsgeschichte genau zu studieren und damit Rückschlüsse auf die Entwicklungsprozesse von Galaxien im Allgemeinen zu ziehen. Insbesondere der chemische Fingerabdruck ihrer Sterne liefert dabei Indizien und Beweise für Ereignisse im Leben der Galaxie.

In den letzten 15 Jahren wurden daher in einer Vielzahl von Himmeldurchmusterungen Millionen von Sternen in der Milchstraße spektroskopisch beobachtet. Die so gewonnenen Informationen bieten detaillierte Einblicke in die Substrukturen unserer Galaxie und deren chemisch-kinematische Struktur. Ergänzend dazu liefern analytische Modelle und numerische Simulationen der Milchstraße wichtige Beschreibungen, die sich zum Vergleich mit Beobachtungen eignen, um die dem komplexen System der Galaxie zugrunde liegenden exakten physikalischen Eigenschaften entschlüsseln zu können.

Die vorliegende Arbeit nutzt verschiedene Ansätze, um moderne theoretische Modelle der Galaxienentstehung und -evolution mit Daten aus stellaren Beobachtungskampagnen zu vergleichen. Die dazu analysierten Beobachtungsdatensätze stammen aus zwei großen Himmelsdurchmusterungen, dem „Radial Velocity Experiment“ (RAVE) und dem „Sloan Extension for Galactic Understanding and Exploration“ (SEGUE). Mit dem Fokus auf der chemisch-kinematischen Struktur der galaktischen Scheibe geht es im Wesentlichen darum, zwei Modelle der Milchstraße zu testen, nämlich ein Populationssynthesemodell (TRILEGAL) und ein Hybridmodell (MCM). Während TRILEGAL auf analytischen Verteilungsfunktionen basiert und zum Ziel hat, die Anzahl und Verteilung der Sterne innerhalb der Galaxie und ihrer unterschiedlichen Komponenten zu simulieren, verbindet das MCM Modell eine kosmologische N-Körper Simulation einer der Milchstraße ähnlichen Galaxie mit einem semi-analytischen Modell zur Beschreibung der chemischen Evolution der Milchstraße. 

Auf Grundlage einer Auswahl von etwa 20000 SEGUE G-Zwergsternen werden in einem ersten Ansatz die aus den Messdaten gewonnenen chemisch-kinematischen Eigenschaften der dünnen und dicken Scheibe der Milchstraße mit den direkten Vorhersagen des MCM Modells verglichen. Eine notwendige Bedingung dafür ist die Korrektur der Beobachtungsdaten für systematische Fehler bei der Objektauswahl der Beobachtungskampagne. Zudem werden mittels einer Bayesischen Methode spektro-photometrische Distanzen mit Fehlern kleiner als 15% für die Auswahl an SEGUE Sternen berechnet, die sich in einer Entfernung von bis zu 3 kpc von der Sonne befinden.

Für den zweiten Ansatz werden basierend auf den oben genannten Modellen zwei synthetische Versionen der SEGUE Himmelsdurchmusterung generiert. Diese künstlichen stellaren Kataloge werden dann verwendet, um Vergleichspseudodatensätze für die verwendeten Zwergsterndaten anzufertigen. Solche synthetischen Testdatensätze eignen sich nicht nur, um die Vorhersagen verschiedener Modelle zu vergleichen, sie können auch zur Validierung der Qualität einzelner Modelle herangezogen werden. Während sich in der Analyse zeigt, dass TRILEGAL sich besonders gut eignet, statistische Eigenschaften der dünnen und dicken galaktischen Scheibe zu reproduzieren, spiegelt das MCM Modell viele der in der Milchstraße beobachtbaren chemisch-kinematischen Korrelationen gut wieder. Trotzdem finden sich Beweise dafür, dass dem MCM Modell eine stellare Komponente fehlt, deren Eigenschaften der in den Beobachtungen sichtbaren dicken Scheibe ähnlich sind.

Meist sind spektroskopische Beobachtungskampagnen auf ein bestimmtes Volumen um die Sonne beschränkt. Oftmals verhindert dies die Möglichkeit einen globalen Blick auf die chemisch-kinematischen Eigenschaften der galaktischen Scheibe zu erlangen. Die Kombination von stellaren Daten unabhängiger Kampagnen ist daher nicht nur nützlich für die Verifikation von Ergebnissen, es hilft auch ein ganzheitlicheres Bild der Galaxie zu erlangen. Die vorliegende Arbeit schließt daher mit einem Vergleich der SEGUE G-Zwergsterne und einer Auswahl von RAVE Riesensternen. Es zeigt sich eine gute Übereinstimmung bzgl. der chemisch-kinematischen Struktur der galaktischen Scheibe besonders in denjenigen Regionen, die von einer Vielzahl von SEGUE und RAVE Objekten abgedeckt werden. Für Regionen des Beobachtungsvolumens, in dem die eine oder die andere der beiden Beobachtungskampagnen eine geringere Statistik von beobachteten Sternen aufweist, ergänzen sich RAVE und SEGUE gut. Dies zeigt, dass nicht nur der Vergleich von Beobachtungen und theoretischen Modellen, sondern auch die Kombination von Messdaten aus verschiedenen Himmelsdurchmusterungen wichtig ist, um die Struktur und die Entstehungsgeschichte der Milchstraße zu verstehen und zu entschlüsseln.
KW  - galaktische Astronomie
KW  - galactic astronomy
KW  - Entstehung der Milchstraße
KW  - Milky Way formation
KW  - Evolution der Milchstraße
KW  - Milky Way evolution
KW  - Milky Way chemo-kinematics
KW  - Chemokinematik der Milchstraße
KW  - SEGUE survey
KW  - SEGUE Beobachtungskampagne
KW  - RAVE survey
KW  - RAVE Beobachtungskampagne
KW  - mock data catalogues
KW  - Pseudodatensätze
Y1  - 2016
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-403968
ER  - 
TY  - THES
A1  - Breitling, Frank
T1  - Propagation of energetic electrons in the solar corona observed with LOFAR
T1  - Ausbreitung energiereicher Elektronen in der Sonnenkorona beobachtet mit LOFAR
N2  - This work reports about new high-resolution imaging and spectroscopic observations of solar type III radio bursts at low radio frequencies in the range from 30 to 80 MHz. Solar type III radio bursts are understood as result of the beam-plasma interaction of electron beams in the corona. The Sun provides a unique opportunity to study these plasma processes of an active star. Its activity appears in eruptive events like flares, coronal mass ejections and radio bursts which are all accompanied by enhanced radio emission. Therefore solar radio emission carries important information about plasma processes associated with the Sun’s activity. Moreover, the Sun’s atmosphere is a unique plasma laboratory with plasma processes under conditions not found in terrestrial laboratories. Because of the Sun’s proximity to Earth, it can be studied in greater detail than any other star but new knowledge about the Sun can be transfer to them. This “solar stellar connection” is important for the understanding of processes on other stars.
The novel radio interferometer LOFAR provides imaging and spectroscopic capabilities to study these processes at low frequencies. Here it was used for solar observations.
LOFAR, the characteristics of its solar data and the processing and analysis of the latter with the Solar Imaging Pipeline and Solar Data Center are described. The Solar Imaging Pipeline is the central software that allows using LOFAR for solar observations. So its development was necessary for the analysis of solar LOFAR data and realized here. Moreover a new density model with heat conduction and Alfvén waves was developed that provides the distance of radio bursts to the Sun from dynamic radio spectra.
Its application to the dynamic spectrum of a type III burst observed on March 16, 2016 by LOFAR shows a nonuniform radial propagation velocity of the radio emission. The analysis of an imaging observation of type III bursts on June 23, 2012 resolves a burst as bright, compact region localized in the corona propagating in radial direction along magnetic field lines with an average velocity of 0.23c. A nonuniform propagation velocity is revealed. A new beam model is presented that explains the nonuniform motion of the radio source as a propagation effect of an electron ensemble with a spread velocity distribution and rules out a monoenergetic electron distribution. The coronal electron number density is derived in the region from 1.5 to 2.5 R☉ and fitted with the newly developed density model. It determines the plasma density for the interplanetary space between Sun and Earth. The values correspond to a 1.25- and 5-fold Newkirk model for harmonic and fundamental emission, respectively. In comparison to data from other radio instruments the LOFAR data shows a high sensitivity and resolution in space, time and frequency.
The new results from LOFAR’s high resolution imaging spectroscopy are consistent with current theories of solar type III radio bursts and demonstrate its capability to track fast moving radio sources in the corona. LOFAR solar data is found to be a valuable source for solar radio physics and opens a new window for studying plasma processes associated with highly energetic electrons in the solar corona.
N2  - Diese Arbeit befasst sich mit neuen hochaufgelösten abbildenden und spektroskopischen Beobachtungen von solaren Typ III Radiobursts bei niedrigen Frequenzen im Bereich von 30 bis 80 MHz. Solare Typ III Radiobursts werden auf die Beam-Plasmawechselwirkung von Elektronenstrahlen in der Korona zurückgeführt. Die Sonne stellt eine einzigartige Möglichkeit dar, diese Plasmaprozesse eines aktiven Sterns zu untersuchen. Die Aktivität zeigt sich in eruptiven Ereignissen wie Flares, koronalen Massenauswürfen und Radiobursts, die jeweils von erhöhter Radiostrahlung begleitet werden. Daher trägt solare Radioemission wichtige Informationen über Plasmaprozesse, die mit Sonnenaktivität in Verbindung stehen. Darüber hinaus ist die Sonne auch ein einzigartiges Plasmalabor mit Plasmaprozessen unter Bedingungen die man nicht in irdischen Laboren findet. Aufgrund ihres vergleichsweise geringen Abstands kann man die Sonne wesentlich genauer beobachten als andere Sterne, aber neue Erkenntnisse von ihr auf andere Sterne übertragen. Diese “Solare-Stellare Verbindung” ist wichtig um Prozesse auf anderen Sternen zu verstehen.
Das neue Radiointerferometer LOFAR bietet abbildende und spektroskopische Möglichkeiten, um diese Prozesse bei niedrigen Frequenzen zu untersuchen und wurde hier für Sonnenbeobachtungen genutzt.
LOFAR, die Besonderheiten seiner Sonnendaten sowie das Verarbeiten und Analysieren dieser Daten mit der Solar Imaging Pipeline und dem Solar Data Center werden beschrieben. Die Solar Imaging Pipeline ist die zentrale Software, die die Nutzung von LOFAR für Sonnenbeobachtungen ermöglicht. Daher war deren Entwicklung für die Analyse von Sonnendaten notwendig und ist im Rahmen dieser Arbeit erfolgt. Außerdem wurde ein neues Dichtemodell mit Wärmeleitung und Alfvén-Wellen entwickelt, welches die Bestimmung der Entfernung von Radiobursts zur Sonne mittels dynamischer Spektren ermöglicht.
Die Anwendung auf dynamische Spektren eines LOFAR Typ III Bursts am 16. März
2016 zeigt eine radiale, ungleichförmige Ausbreitungsgeschwindigkeit der Radioemission. Die Analyse einer abbildenden Beobachtung von Typ III Bursts am 23. Juni
2012 zeigt den Burst als helle, kompakte Region in der Korona die sich in radiale Richtung entlang magnetischer Feldlinien mit einer durchschnittlichen Geschwindigkeit von 0.23c (c, Lichtgeschwindigkeit) bewegt. Die Geschwindigkeit ist nicht gleichförmig. Ein neues Beammodell wird vorgestellt, dass diese ungleichförmige Geschwindigkeit als Ausbreitungseffekt eines Elektronenensemble mit einer ausgedehnten Geschwindigkeitsverteilung erklärt und eine monoenergetische Elektronenverteilung ausschließt. Die koronale Elektronenzahldichte wird in der Region von 1.5 bis 2.5 R☉ ermittelt und ein Fit mit dem neuen Dichtemodell durchgeführt. Dadurch ist die Plasmadichte im ganzen interplanetaren Raum zwischen Sonne und Erde bestimmt. Die Werte entsprechen jeweils einem 1.25- und 5-fachen Newkirk Modell im Fall von fundamentaler und harmonischer Emission. Im Vergleich zu Daten von anderen Radioinstrumenten haben LOFAR-Daten eine hohe Empfindlichkeit und Auflösung in Raum, Zeit und Frequenz.
Die neuen Ergebnisse von LOFARs hochauflösender, abbildender Spektroskopie stimmen mit derzeitigen Theorien von solaren Typ III Radiobursts überein und zeigen die Möglichkeit, schnell bewegliche Radioquellen in der Korona zu verfolgen. LOFAR Sonnendaten wurden als wertvolle Quelle für solare Radiophysik erkannt und öffnen eine neues Fenster zur Untersuchung von Plasmaprozessen hochenergetischer Elektronen in der Korona.
KW  - sun
KW  - type III
KW  - radio burst
KW  - LOFAR
KW  - plasma physics
KW  - Sonne
KW  - Typ III
KW  - Radioburst
KW  - Plasmaphysik
Y1  - 2016
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-396893
ER  - 
TY  - JOUR
A1  - Brose, Robert
A1  - Telezhinsky, Igor O.
A1  - Pohl, Martin
T1  - Transport of magnetic turbulence in supernova remnants
JF  - Physical review letters
N2  - Context. Supernova remnants are known as sources of Galactic cosmic rays for their nonthermal emission of radio waves, X-rays, and gamma rays. However, the observed soft broken power-law spectra are hard to reproduce within standard acceleration theory based on the assumption of Bohm diffusion and steady-state calculations. Aims. We point out that a time-dependent treatment of the acceleration process together with a self-consistent treatment of the scattering turbulence amplification is necessary. Methods. We numerically solve the coupled system of transport equations for cosmic rays and isotropic Alfvenic turbulence. The equations are coupled through the growth rate of turbulence determined by the cosmic-ray gradient and the spatial diffusion coefficient of cosmic rays determined by the energy density of the turbulence. The system is solved on a comoving expanding grid extending upstream for dozens of shock radii, allowing for the self-consistent study of cosmic-ray diffusion in the vicinity of their acceleration site. The transport equation for cosmic rays is solved in a test-particle approach. Results. We demonstrate that the system is typically not in a steady state. In fact, even after several thousand years of evolution, no equilibrium situation is reached. The resulting time-dependent particle spectra strongly differ from those derived assuming a steady state and Bohm diffusion. Our results indicate that proper accounting for the evolution of the scattering turbulence and hence the particle diffusion coefficient is crucial for the formation of the observed soft spectra. In any case, the need to continuously develop magnetic turbulence upstream of the shock introduces nonlinearity in addition to that imposed by cosmic-ray feedback.
KW  - ISM: supernova remnants
KW  - acceleration of particles
KW  - turbulence
Y1  - 2016
U6  - https://doi.org/10.1051/0004-6361/201527345
SN  - 1432-0746
VL  - 593
PB  - EDP Sciences
CY  - Les Ulis
ER  - 
TY  - GEN
A1  - Bürger, Andreas
A1  - Magdans, Uta
A1  - Gies, Hermann
T1  - Adsorption of amino acids on the magnetite-(111)-surface: a force field study (vol 19, 851, 2013)
T2  - Journal of molecular modeling
Y1  - 2016
U6  - https://doi.org/10.1007/s00894-016-3124-8
SN  - 1610-2940
SN  - 0948-5023
VL  - 22
PB  - Springer
CY  - New York
ER  - 
TY  - JOUR
A1  - Chen, Xuhui
A1  - Pohl, Martin
A1  - Bottcher, Markus
A1  - Gao, Shan
T1  - Particle diffusion and localized acceleration in inhomogeneous AGN jets - II. Stochastic variation
JF  - Monthly notices of the Royal Astronomical Society
N2  - We study the stochastic variation of blazar emission under a 2D spatially resolved leptonic jet model we previously developed. Random events of particle acceleration and injection in small zones within the emission region are assumed to be responsible for flux variations. In addition to producing spectral energy distributions that describe the observed flux of Mrk 421, we further analyse the timing properties of the simulated light curves, such as the power spectral density (PSD) at different bands, flux-flux correlations, aswell as the cross-correlation function between X-rays and TeV gamma-rays. We find spectral breaks in the PSD at a time-scale comparable to the dominant characteristic time-scale in the system, which is usually the predefined decay time-scale of an acceleration event. Cooling imposes a delay, and so PSDs taken at lower energy bands in each emission component (synchrotron or inverse Compton) generally break at longer time-scales. The flux-flux correlation between X-rays and TeV gamma-rays can be either quadratic or linear, depending on whether or not there are large variation of the injection into the particle acceleration process. When the relationship is quadratic, the TeV flares lag the X-ray flares, and the optical and GeV flares are large enough to be comparable to the ones in X-ray. When the relationship is linear, the lags are insignificant, and the optical and GeV flares are small.
KW  - acceleration of particles
KW  - diffusion
KW  - radiation mechanisms: non-thermal
KW  - galaxies: active
KW  - BL Lacertae objects: individual: Mrk 421
KW  - galaxies: jets
Y1  - 2016
U6  - https://doi.org/10.1093/mnras/stw528
SN  - 0035-8711
SN  - 1365-2966
VL  - 458
SP  - 3260
EP  - 3271
PB  - Oxford Univ. Press
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Cherstvy, Andrey G.
A1  - Metzler, Ralf
T1  - Anomalous diffusion in time-fluctuating non-stationary diffusivity landscapes
JF  - Physical chemistry, chemical physics : PCCP ; a journal of European chemical societies
N2  - We investigate the ensemble and time averaged mean squared displacements for particle diffusion in a simple model for disordered media by assuming that the local diffusivity is both fluctuating in time and has a deterministic average growth or decay in time. In this study we compare computer simulations of the stochastic Langevin equation for this random diffusion process with analytical results. We explore the regimes of normal Brownian motion as well as anomalous diffusion in the sub- and superdiffusive regimes. We also consider effects of the inertial term on the particle motion. The investigation of the resulting diffusion is performed for unconfined and confined motion.
Y1  - 2016
U6  - https://doi.org/10.1039/C6CP03101C
SN  - 1463-9084
SN  - 1463-9076
VL  - 18
SP  - 23840
EP  - 23852
PB  - RSC Publ.
CY  - Cambridge
ER  - 
TY  - GEN
A1  - Cherstvy, Andrey G.
A1  - Metzler, Ralf
T1  - Anomalous diffusion in time-fluctuating non-stationary diffusivity landscapes
N2  - We investigate the ensemble and time averaged mean squared displacements for particle diffusion in a simple model for disordered media by assuming that the local diffusivity is both fluctuating in time and has a deterministic average growth or decay in time. In this study we compare computer simulations of the stochastic Langevin equation for this random diffusion process with analytical results. We explore the regimes of normal Brownian motion as well as anomalous diffusion in the sub- and superdiffusive regimes. We also consider effects of the inertial term on the particle motion. The investigation of the resulting diffusion is performed for unconfined and confined motion.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 257 
Y1  - 2016
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-95901
SP  - 23840
EP  - 23852
ER  - 
TY  - JOUR
A1  - Cherstvy, Andrey G.
A1  - Metzler, Ralf
T1  - Anomalous diffusion in time-fluctuating non-stationary diffusivity landscapes
JF  - Physical chemistry, chemical physics : a journal of European Chemical Societies
N2  - We investigate the ensemble and time averaged mean squared displacements for particle diffusion in a simple model for disordered media by assuming that the local diffusivity is both fluctuating in time and has a deterministic average growth or decay in time. In this study we compare computer simulations of the stochastic Langevin equation for this random diffusion process with analytical results. We explore the regimes of normal Brownian motion as well as anomalous diffusion in the sub- and superdiffusive regimes. We also consider effects of the inertial term on the particle motion. The investigation of the resulting diffusion is performed for unconfined and confined motion.
Y1  - 2016
U6  - https://doi.org/10.1039/c6cp03101c
SN  - 1463-9076
SN  - 1463-9084
VL  - 18
SP  - 23840
EP  - 23852
PB  - Royal Society of Chemistry
CY  - Cambridge
ER  - 
TY  - JOUR
A1  - Cioni, Maria-Rosa L.
A1  - Bekki, Kenji
A1  - Girardi, Leo
A1  - de Grijs, Richard
A1  - Irwin, Mike J.
A1  - Ivanov, Valentin D.
A1  - Marconi, Marcella
A1  - Oliveira, Joana M.
A1  - Piatti, Andres E.
A1  - Ripepi, Vincenzo
A1  - van Loon, Jacco Th.
T1  - XVII. Proper motions of the Small Magellanic Cloud and the Milky Way globular cluster 47 Tucanae
JF  - Physical review : E, Statistical, nonlinear and soft matter physics
N2  - Aims. In this study we use multi-epoch near-infrared observations from the VISTA survey of the Magellanic Cloud system (VMC) to measure the proper motions of different stellar populations in a tile of 1.5 deg2 in size in the direction of the Galactic globular cluster 47 Tuc. We obtain the proper motion of the cluster itself, of the Small Magellanic Cloud (SMC), and of the field Milky Way stars.

Methods. Stars of the three main stellar components are selected according to their spatial distributions and their distributions in colour&#8722;magnitude diagrams. Their average coordinate displacement is computed from the difference between multiple Ks-band observations for stars as faint as Ks = 19 mag. Proper motions are derived from the slope of the best-fitting line among ten VMC epochs over a time baseline of ~1 yr. Background galaxies are used to calibrate the absolute astrometric reference frame.

Results. The resulting absolute proper motion of 47 Tuc is (&#956;&#945;cos(&#948;), &#956;&#948;) = (+7.26 ± 0.03, &#8722;1.25 ± 0.03) mas yr-1. This measurement refers to about 35 000 sources distributed between 10&#8242; and 60&#8242; from the cluster centre. For the SMC we obtain (&#956;&#945;cos(&#948;), &#956;&#948;) = (+1.16 ± 0.07, &#8722;0.81 ± 0.07) mas yr-1 from about 5250 red clump and red giant branch stars. The absolute proper motion of the Milky Way population in the line of sight (l = 305.9, b = &#8722;44.9) of this VISTA tile is (&#956;&#945;cos(&#948;), &#956;&#948;) = (+10.22 ± 0.14, &#8722;1.27 ± 0.12) mas yr-1 and has been calculated from about 4000 sources. Systematic uncertainties associated with the astrometric reference system are 0.18 mas yr-1. Thanks to the proper motion we detect 47 Tuc stars beyond its tidal radius.
KW  - proper motions
KW  - surveys
KW  - Magellanic Clouds
KW  - globular clusters: individual: 47 Tucanae
Y1  - 2016
U6  - https://doi.org/10.1051/0004-6361/201527004
SN  - 1432-0746
VL  - 586
SP  - 67
EP  - 75
PB  - EDP Sciences
CY  - Les Ulis
ER  - 
TY  - JOUR
A1  - Clark, Peter U.
A1  - Shakun, Jeremy D.
A1  - Marcott, Shaun A.
A1  - Mix, Alan C.
A1  - Eby, Michael
A1  - Kulp, Scott
A1  - Levermann, Anders
A1  - Milne, Glenn A.
A1  - Pfister, Patrik L.
A1  - Santer, Benjamin D.
A1  - Schrag, Daniel P.
A1  - Solomon, Susan
A1  - Stocker, Thomas F.
A1  - Strauss, Benjamin H.
A1  - Weaver, Andrew J.
A1  - Winkelmann, Ricarda
A1  - Archer, David
A1  - Bard, Edouard
A1  - Goldner, Aaron
A1  - Lambeck, Kurt
A1  - Pierrehumbert, Raymond T.
A1  - Plattner, Gian-Kasper
T1  - Consequences of twenty-first-century policy for multi-millennial climate
and sea-level change
JF  - Nature climate change
N2  - Most of the policy debate surrounding the actions needed to mitigate and adapt to anthropogenic climate change has been framed by observations of the past 150 years as well as climate and sea-level projections for the twenty-first century. The focus on this 250-year window, however, obscures some of the most profound problems associated with climate change. Here, we argue that the twentieth and twenty-first centuries, a period during which the overwhelming majority of human-caused carbon emissions are likely to occur, need to be placed into a long-term context that includes the past 20 millennia, when the last Ice Age ended and human civilization developed, and the next ten millennia, over which time the projected impacts of anthropogenic climate change will grow and persist. This long-term perspective illustrates that policy decisions made in the next few years to decades will have profound impacts on global climate, ecosystems and human societies - not just for this century, but for the next ten millennia and beyond.
Y1  - 2016
U6  - https://doi.org/10.1038/NCLIMATE2923
SN  - 1758-678X
SN  - 1758-6798
VL  - 6
SP  - 360
EP  - 369
PB  - Nature Publ. Group
CY  - London
ER  - 
TY  - JOUR
A1  - Clusella, Pau
A1  - Politi, Antonio
A1  - Rosenblum, Michael
T1  - A minimal model of self-consistent partial synchrony
JF  - NEW JOURNAL OF PHYSICS
N2  - We show that self-consistent partial synchrony in globally coupled oscillatory ensembles is a general phenomenon. We analyze in detail appearance and stability properties of this state in possibly the simplest setup of a biharmonic Kuramoto-Daido phase model as well as demonstrate the effect in limit-cycle relaxational Rayleigh oscillators. Such a regime extends the notion of splay state from a uniform distribution of phases to an oscillating one. Suitable collective observables such as the Kuramoto order parameter allow detecting the presence of an inhomogeneous distribution. The characteristic and most peculiar property of self-consistent partial synchrony is the difference between the frequency of single units and that of the macroscopic field.
KW  - synchronization
KW  - collective dynamics
KW  - coupled oscillators
Y1  - 2016
U6  - https://doi.org/10.1088/1367-2630/18/9/093037
SN  - 1367-2630
VL  - 18
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - THES
A1  - Daschewski, Maxim
T1  - Thermophony in real gases
T1  - Das Thermophon
BT  - theory and applications
BT  - Theorie und Anwendung
N2  - A thermophone is an electrical device for sound generation. The advantages of thermophones over conventional sound transducers such as electromagnetic, electrostatic or piezoelectric transducers are their operational principle which does not require any moving parts, their resonance-free behavior, their simple construction and their low production costs. 
In this PhD thesis, a novel theoretical model of thermophonic sound generation in real gases has been developed. The model is experimentally validated in a frequency range from 2 kHz to 1 MHz by testing more then fifty thermophones of different materials, including Carbon nano-wires, Titanium, Indium-Tin-Oxide, different sizes and shapes for sound generation in gases such as air, argon, helium, oxygen, nitrogen and sulfur hexafluoride.
Unlike previous approaches, the presented model can be applied to different kinds of thermophones and various gases, taking into account the thermodynamic properties of thermophone materials and of adjacent gases, degrees of freedom and the volume occupied by the gas atoms and molecules, as well as sound attenuation effects, the shape and size of the thermophone surface and the reduction of the generated acoustic power due to photonic emission. As a result, the model features better prediction accuracy than the existing models by a factor up to 100. Moreover, the new model explains previous experimental findings on thermophones which can not be explained with the existing models. 
The acoustic properties of the thermophones have been tested in several gases using unique, highly precise experimental setups comprising a Laser-Doppler-Vibrometer combined with a thin polyethylene film which acts as a broadband and resonance-free sound-pressure detector. Several outstanding properties of the thermophones have been demonstrated for the first time, including the ability to generate arbitrarily shaped acoustic signals, a greater acoustic efficiency compared to conventional piezoelectric and electrostatic airborne ultrasound transducers, and applicability as powerful and tunable sound sources with a bandwidth up to the megahertz range and beyond. 
Additionally, new applications of thermophones such as the study of physical properties of gases, the thermo-acoustic gas spectroscopy, broad-band characterization of transfer functions of sound and ultrasound detection systems, and applications in non-destructive materials testing are discussed and experimentally demonstrated.
N2  - Ein Thermophon ist ein elektrisches Gerät zur Schallerzeugung. Aufgrund der fehlenden beweglichen Teile verfügen Thermophone über mehrere Vorteile gegenüber den herkömmlichen elektromagnetischen, elektrostatischen oder piezoelektrischen Schallwandlern. Besonders bemerkenswert sind das resonanz- und nachschwingungsfreie Verhalten, die einfache Konstruktion und die niedrigen Herstellungskosten.
Im Rahmen dieser Doktorarbeit wurde ein neuartiges theoretisches Modell der thermophonischen Schallerzeugung in Gasen entwickelt und experimentell verifiziert. Zur Validierung des Modells wurden mehr als fünfzig Thermophone unterschiedlicher Größen,  Formen und Materialien, darunter Kohlenstoff-Nanodrähte, Titan und Indium-Zinnoxid zur Erzeugung von Schall in Gasen wie Luft, Argon, Helium, Sauerstoff, Stickstoff und Schwefelhexafluorid in einem Frequenzbereich von 2 kHz bis 1 MHz eingesetzt.
Das präsentierte Modell unterscheidet sich von den bisherigen Ansätzen durch seine hohe Flexibilität, wobei die thermodynamischen Eigenschaften des Thermophons und des umgebenden Gases, die Freiheitsgrade und das Eigenvolumen der Gasatome und Moleküle, die Schallschwächungseffekte, die Form und Größe des Thermophons, sowie die Verringerung der erzeugten akustischen Leistung aufgrund der Photonenemission berücksichtigt werden. Infolgedessen zeigt das entwickelte Modell eine um bis zu einem Faktor 100 höhere Vorhersagegenauigkeit als die bisher veröffentlichten Modelle. Das präsentierte Modell liefert darüber hinaus eine Erklärung zu den Ergebnissen aus den Vorarbeiten, die von den bisherigen Modellen nicht abschließend geklärt werden konnten.
Die akustischen Eigenschaften der Thermophone wurden unter Verwendung von einzigartigen hochpräzisen Versuchsaufbauten getestet. Dafür wurde ein Laser-Doppler-Vibrometer in Kombination mit einer dünnen Polyethylenfolie verwendet, welche als breitbrandiger und resonanzfreier Schalldruckdetektor fungiert. Somit konnten mehrere herausragende akustische Eigenschaften der Thermophone zum ersten Mal demonstriert werden, einschließlich der Möglichkeit, beliebig geformte akustische Signale zu erzeugen, eine größere akustische Wirksamkeit im Vergleich zu herkömmlichen Luftultraschallwandlern und die Anwendbarkeit als leistungsfähige beliebig abstimmbare Schallquellen mit einer Bandbreite bis in den Megahertz-Bereich. 
Zusätzlich werden neue Anwendungen von Thermophonen wie die Untersuchung der physikalischen Eigenschaften von Gasen, die thermoakustische Gasspektroskopie, eine breitbandige Charakterisierung der Übertragungsfunktionen von Schall- und Ultraschallmesssystemen und Anwendungen in der zerstörungsfreien Materialprüfung demonstriert.
KW  - thermophone
KW  - thermoacoustics
KW  - thermoacoustic effect
KW  - photoacoustic effect
KW  - Thermophon
KW  - Thermoakustik
KW  - thermoakustischer Effekt
KW  - photoakustischer Effekt
Y1  - 2016
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-98866
ER  - 
TY  - JOUR
A1  - de Carvalho, Sidney J.
A1  - Metzler, Ralf
A1  - Cherstvy, Andrey G.
T1  - Critical adsorption of polyelectrolytes onto planar and convex highly charged surfaces
BT  - the nonlinear Poisson–Boltzmann approach
JF  - New journal of physics : the open-access journal for physics
N2  - We study the adsorption–desorption transition of polyelectrolyte chains onto planar, cylindrical and spherical surfaces with arbitrarily high surface charge densities by massive Monte Carlo computer simulations. We examine in detail how the well known scaling relations for the threshold transition—demarcating the adsorbed and desorbed domains of a polyelectrolyte near weakly charged surfaces—are altered for highly charged interfaces. In virtue of high surface potentials and large surface charge densities, the Debye–Hückel approximation is often not feasible and the nonlinear Poisson–Boltzmann approach should be implemented. At low salt conditions, for instance, the electrostatic potential from the nonlinear Poisson–Boltzmann equation is smaller than the Debye–Hückel result, such that the required critical surface charge density for polyelectrolyte adsorption σc increases. The nonlinear relation between the surface charge density and electrostatic potential leads to a sharply increasing critical surface charge density with growing ionic strength, imposing an additional limit to the critical salt concentration above which no polyelectrolyte adsorption occurs at all. We contrast our simulations findings with the known scaling results for weak critical polyelectrolyte adsorption onto oppositely charged surfaces for the three standard geometries. Finally, we discuss some applications of our results for some physical–chemical and biophysical systems.
KW  - polyelectrolyte adsorption
KW  - electrostatic interactions
KW  - critical phenomena
KW  - Debye screening
Y1  - 2016
U6  - https://doi.org/10.1088/1367-2630/18/8/083037
SN  - 1367-2630
VL  - 18
PB  - IOP Publ.
CY  - London
ER  - 
TY  - GEN
A1  - de Carvalho, Sidney J.
A1  - Metzler, Ralf
A1  - Cherstvy, Andrey G.
T1  - Critical adsorption of polyelectrolytes onto planar and convex highly charged surfaces
BT  - the nonlinear Poisson–Boltzmann approach
N2  - We study the adsorption–desorption transition of polyelectrolyte chains onto planar, cylindrical and spherical surfaces with arbitrarily high surface charge densities by massive Monte Carlo computer simulations. We examine in detail how the well known scaling relations for the threshold transition—demarcating the adsorbed and desorbed domains of a polyelectrolyte near weakly charged surfaces—are altered for highly charged interfaces. In virtue of high surface potentials and large surface charge densities, the Debye–Hückel approximation is often not feasible and the nonlinear Poisson–Boltzmann approach should be implemented. At low salt conditions, for instance, the electrostatic potential from the nonlinear Poisson–Boltzmann equation is smaller than the Debye–Hückel result, such that the required critical surface charge density for polyelectrolyte adsorption σc increases. The nonlinear relation between the surface charge density and electrostatic potential leads to a sharply increasing critical surface charge density with growing ionic strength, imposing an additional limit to the critical salt concentration above which no polyelectrolyte adsorption occurs at all. We contrast our simulations findings with the known scaling results for weak critical polyelectrolyte adsorption onto oppositely charged surfaces for the three standard geometries. Finally, we discuss some applications of our results for some physical–chemical and biophysical systems.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 292 
KW  - polyelectrolyte adsorption
KW  - electrostatic interactions
KW  - critical phenomena
KW  - Debye screening
Y1  - 2016
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-100295
ER  - 
TY  - JOUR
A1  - de Carvalho, Sidney J.
A1  - Metzler, Ralf
A1  - Cherstvy, Andrey G.
T1  - Critical adsorption of polyelectrolytes onto planar and convex highly charged surfaces: the nonlinear Poisson-Boltzmann approach
JF  - NEW JOURNAL OF PHYSICS
N2  - We study the adsorption-desorption transition of polyelectrolyte chains onto planar, cylindrical and spherical surfaces with arbitrarily high surface charge densities by massive Monte Carlo computer simulations. We examine in detail how the well known scaling relations for the threshold transition demarcating the adsorbed and desorbed domains of a polyelectrolyte near weakly charged surfaces-are altered for highly charged interfaces. In virtue of high surface potentials and large surface charge densities, the Debye-Huckel approximation is often not feasible and the nonlinear Poisson-Boltzmann approach should be implemented. At low salt conditions, for instance, the electrostatic potential from the nonlinear Poisson-Boltzmann equation is smaller than the Debye-Huckel result, such that the required critical surface charge density for polyelectrolyte adsorption sigma(c) increases. The nonlinear relation between the surface charge density and electrostatic potential leads to a sharply increasing critical surface charge density with growing ionic strength, imposing an additional limit to the critical salt concentration above which no polyelectrolyte adsorption occurs at all. We contrast our simulations findings with the known scaling results for weak critical polyelectrolyte adsorption onto oppositely charged surfaces for the three standard geometries. Finally, we discuss some applications of our results for some physical-chemical and biophysical systems.
KW  - polyelectrolyte adsorption
KW  - electrostatic interactions
KW  - critical phenomena
KW  - Debye screening
Y1  - 2016
U6  - https://doi.org/10.1088/1367-2630/18/8/083037
SN  - 1367-2630
VL  - 18
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Denker, Carsten
A1  - Heibel, C.
A1  - Rendtel, J.
A1  - Arlt, K.
A1  - Balthasar, H.
A1  - Diercke, Andrea
A1  - Gonzalez Manrique, Sergio Javier
A1  - Hofmann, A.
A1  - Kuckein, Christoph
A1  - Önel, H.
A1  - Valliappan, Senthamizh Pavai
A1  - Staude, J.
A1  - Verma, Meetu
T1  - Solar physics at the Einstein Tower
JF  - Astronomische Nachrichten = Astronomical notes
KW  - history and philosophy of astronomy
KW  - Sun: photosphere
KW  - Sun: magnetic fields
KW  - techniques: spectroscopic
KW  - telescopes
Y1  - 2016
U6  - https://doi.org/10.1002/asna.201612442
SN  - 0004-6337
SN  - 1521-3994
VL  - 337
SP  - 1105
EP  - 1113
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Di Pietro, Riccardo
A1  - Nasrallah, Iyad
A1  - Carpenter, Joshua
A1  - Gann, Eliot
A1  - Kölln, Lisa Sophie
A1  - Thomsen, Lars
A1  - Venkateshvaran, Deepak
A1  - Sadhanala, Aditya
A1  - Chabinyc, Michael
A1  - McNeill, Christopher R.
A1  - Facchetti, Antonio
A1  - Ade, Harald W.
A1  - Sirringhaus, Henning
A1  - Neher, Dieter
T1  - Coulomb Enhanced Charge Transport in Semicrystalline Polymer Semiconductors
JF  - Advanced functional materials
Y1  - 2016
U6  - https://doi.org/10.1002/adfm.201602080
SN  - 1616-301X
SN  - 1616-3028
VL  - 26
SP  - 8011
EP  - 8022
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - THES
A1  - Dionysopoulou, Kyriaki
T1  - General-relativistic magnetohydrodynamics in compact objects
BT  - a resistive-magnetohydrodynamics approach
Y1  - 2016
ER  - 
TY  - JOUR
A1  - Dzhanoev, Arsen R.
A1  - Schmidt, J.
A1  - Liu, X.
A1  - Spahn, Frank
T1  - Charging of small grains in a space plasma: Application to Jovian stream particles
JF  - International psychogeriatrics
N2  - Context. Most theoretical investigations of dust charging processes in space have treated the current balance condition as independent of grain size. However, for small grains, since they are often observed in space environments, a dependence on grain size is expected owing to secondary electron emission (SEE). Here, by the term "small" we mean a particle size comparable to the typical penetration depth for given primary electron energy. The results are relevant for the dynamics of small, charged dust particles emitted by the volcanic moon Io, which forms the Jovian dust streams. Aims. We revise the theory of charging of small (submicron sized) micrometeoroids to take into account a high production of secondary electrons for small grains immersed in an isotropic flux of electrons. We apply our model to obtain an improved estimate for the charge of the dust streams leaving the Jovian system, detected by several spacecraft. Methods. We apply a continuum model to describe the penetration of primary electrons in a grain and the emission of secondary electrons along the path. Averaging over an isotropic flux of primaries, we derive a new expression for the secondary electron yield, which can be used to express the secondary electron current on a grain. Results. For the Jupiter plasma environment we derive the surface potential of grains composed of NaCl (believed to be the major constituent of Jovian dust stream particles) or silicates. For small particles, the potential depends on grain size and the secondary electron current induces a sensitivity to material properties. As a result of the small particle effect, the estimates for the charging times and for the fractional charge fluctuations of NaCl grains obtained using our general approach to SEE give results qualitatively different from the analogous estimates derived from the traditional approach to SEE. We find that for the charging environment considered in this paper field emission does not limit the charging of NaCl grains.
KW  - plasmas
KW  - planets and satellites: individual: Jupiter
Y1  - 2016
U6  - https://doi.org/10.1051/0004-6361/201527891
SN  - 1432-0746
VL  - 591
SP  - 647
EP  - 684
PB  - EDP Sciences
CY  - Les Ulis
ER  - 
TY  - JOUR
A1  - Eckert, Sebastian
A1  - Miedema, P. S.
A1  - Quevedo, W.
A1  - Fondell, Mattis
A1  - Beye, Martin
A1  - Pietzsch, Annette
A1  - Ross, M.
A1  - Khalil, M.
A1  - Föhlisch, Alexander
T1  - Molecular structures and protonation state of 2-Mercaptopyridine in aqueous solution
JF  - Chemical physics letters
N2  - The speciation of 2-Mercaptopyridine in aqueous solution has been investigated with nitrogen 1s Near Edge X-ray Absorption Fine Structure spectroscopy and time dependent Density Functional Theory. The prevalence of distinct species as a function of the solvent basicity is established. No indications of dimerization towards high concentrations are found. The determination of different molecular structures of 2-Mercaptopyridine in aqueous solution is put into the context of proton-transfer in keto-enol and thione-thiol tautomerisms. (C) 2016 The Authors. Published by Elsevier B.V.
Y1  - 2016
U6  - https://doi.org/10.1016/j.cplett.2016.01.050
SN  - 0009-2614
SN  - 1873-4448
VL  - 647
SP  - 103
EP  - 106
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Fang, Lijia
A1  - Holzmueller, Felix
A1  - Matulaitis, Tomas
A1  - Baasner, Anne
A1  - Hauenstein, Christoph
A1  - Benduhn, Johannes
A1  - Schwarze, Martin
A1  - Petrich, Annett
A1  - Piersimoni, Fortunato
A1  - Scholz, Reinhard
A1  - Zeika, Olaf
A1  - Koerner, Christian
A1  - Neher, Dieter
A1  - Vandewal, Koen
A1  - Leo, Karl
T1  - Fluorine-containing low-energy-gap organic dyes with low voltage losses for organic solar cells
JF  - Synthetic metals : the journal of electronic polymers and electronic molecular materials
N2  - Fluorine-containing donor molecules TFTF, CNTF and PRTF are designed and isomer selectively synthesized for application in vacuum-deposited organic solar cells. These molecules comprise a donor acceptor molecular architecture incorporating thiophene and benzothiadiazole derivatives as the electron-donating and electron-withdrawing moieties, respectively. As opposed to previously reported materials from this class, PRTF can be purified by vacuum sublimation at moderate to high yields because of its higher volatility and better stabilization due to a stronger intramolecular hydrogen bond, as compared to TFTF and CNTF. The UV-vis absorption spectra of the three donors show an intense broadband absorption between 500 nm and 800 nm with, similar positions of their frontier energy levels. The photophysical properties of the three donor molecules are thoroughly tested and optimized in bulk heterojunction solar cells with C-60 as acceptor. PRTF shows the best performance, yielding power conversion efficiencies of up to 3.8%. Moreover, the voltage loss for the PRTF device due to the non radiative recombination of free charge carriers is exceptionally low (0.26 V) as compared to typical values for organic solar cells (>0.34V). (C) 2016 Published by Elsevier B.V.
KW  - (Z)-isomer
KW  - Donor materials
KW  - CH center dot center dot center dot F hydrogen bonds
KW  - Sublimation with good yield
KW  - Low voltage losses
Y1  - 2016
U6  - https://doi.org/10.1016/j.synthmet.2016.10.025
SN  - 0379-6779
VL  - 222
SP  - 232
EP  - 239
PB  - Elsevier
CY  - Lausanne
ER  - 
TY  - JOUR
A1  - Feldmann, David
A1  - Maduar, Salim R.
A1  - Santer, Mark
A1  - Lomadze, Nino
A1  - Vinogradova, Olga I.
A1  - Santer, Svetlana
T1  - Manipulation of small particles at solid liquid interface: light driven diffusioosmosis
JF  - Scientific reports
N2  - The strong adhesion of sub-micron sized particles to surfaces is a nuisance, both for removing contaminating colloids from surfaces and for conscious manipulation of particles to create and test novel micro/nano-scale assemblies. The obvious idea of using detergents to ease these processes suffers from a lack of control: the action of any conventional surface-modifying agent is immediate and global. With photosensitive azobenzene containing surfactants we overcome these limitations. Such photo-soaps contain optical switches (azobenzene molecules), which upon illumination with light of appropriate wavelength undergo reversible trans-cis photo-isomerization resulting in a subsequent change of the physico-chemical molecular properties. In this work we show that when a spatial gradient in the composition of trans-and cis-isomers is created near a solid-liquid interface, a substantial hydrodynamic flow can be initiated, the spatial extent of which can be set, e.g., by the shape of a laser spot. We propose the concept of light induced diffusioosmosis driving the flow, which can remove, gather or pattern a particle assembly at a solid-liquid interface. In other words, in addition to providing a soap we implement selectivity: particles are mobilized and moved at the time of illumination, and only across the illuminated area.
Y1  - 2016
U6  - https://doi.org/10.1038/srep36443
SN  - 2045-2322
VL  - 6
SP  - 25083
EP  - 25091
PB  - Nature Publ. Group
CY  - London
ER  - 
TY  - JOUR
A1  - Feldmann, David
A1  - Maduar, Salim R.
A1  - Santer, Mark
A1  - Lomadze, Nino
A1  - Vinogradova, Olga I.
A1  - Santer, Svetlana
T1  - Manipulation of small particles at solid liquid interface
BT  - light driven diffusioosmosis
JF  - Scientific reports
N2  - The strong adhesion of sub-micron sized particles to surfaces is a nuisance, both for removing contaminating colloids from surfaces and for conscious manipulation of particles to create and test novel micro/nano-scale assemblies. The obvious idea of using detergents to ease these processes suffers from a lack of control: the action of any conventional surface-modifying agent is immediate and global. With photosensitive azobenzene containing surfactants we overcome these limitations. Such photo-soaps contain optical switches (azobenzene molecules), which upon illumination with light of appropriate wavelength undergo reversible trans-cis photo-isomerization resulting in a subsequent change of the physico-chemical molecular properties. In this work we show that when a spatial gradient in the composition of trans- and cis- isomers is created near a solid-liquid interface, a substantial hydrodynamic flow can be initiated, the spatial extent of which can be set, e.g., by the shape of a laser spot. We propose the concept of light induced diffusioosmosis driving the flow, which can remove, gather or pattern a particle assembly at a solid-liquid interface. In other words, in addition to providing a soap we implement selectivity: particles are mobilized and moved at the time of illumination, and only across the illuminated area.
KW  - genomic DNA conformation
KW  - photosensitive surfactants
KW  - optical manipulation
KW  - photocontrol
KW  - azobenzene
KW  - films
KW  - gradients
KW  - transport
KW  - tracking
KW  - brushes
Y1  - 2016
U6  - https://doi.org/10.1038/srep36443
SN  - 2045-2322
VL  - 6
PB  - Nature Publishing Group
CY  - London
ER  - 
TY  - GEN
A1  - Feldmann, David
A1  - Maduar, Salim R.
A1  - Santer, Mark
A1  - Lomadze, Nino
A1  - Vinogradova, Olga I.
A1  - Santer, Svetlana
T1  - Manipulation of small particles at solid liquid interface
BT  - light driven diffusioosmosis
N2  - The strong adhesion of sub-micron sized particles to surfaces is a nuisance, both for removing contaminating colloids from surfaces and for conscious manipulation of particles to create and test novel micro/nano-scale assemblies. The obvious idea of using detergents to ease these processes suffers from a lack of control: the action of any conventional surface-modifying agent is immediate and global. With photosensitive azobenzene containing surfactants we overcome these limitations. Such photo-soaps contain optical switches (azobenzene molecules), which upon illumination with light of appropriate wavelength undergo reversible trans-cis photo-isomerization resulting in a subsequent change of the physico-chemical molecular properties. In this work we show that when a spatial gradient in the composition of trans- and cis- isomers is created near a solid-liquid interface, a substantial hydrodynamic flow can be initiated, the spatial extent of which can be set, e.g., by the shape of a laser spot. We propose the concept of light induced diffusioosmosis driving the flow, which can remove, gather or pattern a particle assembly at a solid-liquid interface. In other words, in addition to providing a soap we implement selectivity: particles are mobilized and moved at the time of illumination, and only across the illuminated area.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 293 
KW  - azobenzene
KW  - brushes
KW  - films
KW  - genomic DNA conformation
KW  - gradients
KW  - optical manipulation
KW  - photocontrol
KW  - photosensitive surfactants
KW  - tracking
KW  - transport
Y1  - 2016
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-100338
ER  - 
TY  - JOUR
A1  - Feldmann, Johannes
A1  - Levermann, Anders
T1  - Similitude of ice dynamics against scaling of geometry and physical parameters
JF  - The Cryosphere : TC ; an interactive open access journal of the European Geosciences Union
N2  - The concept of similitude is commonly employed in the fields of fluid dynamics and engineering but rarely used in cryospheric research. Here we apply this method to the problem of ice flow to examine the dynamic similitude of isothermal ice sheets in shallow-shelf approximation against the scaling of their geometry and physical parameters. Carrying out a dimensional analysis of the stress balance we obtain dimensionless numbers that characterize the flow. Requiring that these numbers remain the same under scaling we obtain conditions that relate the geometric scaling factors, the parameters for the ice softness, surface mass balance and basal friction as well as the ice-sheet intrinsic response time to each other. We demonstrate that these scaling laws are the same for both the (two-dimensional) flow-line case and the three-dimensional case. The theoretically predicted ice-sheet scaling behavior agrees with results from numerical simulations that we conduct in flow-line and three-dimensional conceptual setups. We further investigate analytically the implications of geometric scaling of ice sheets for their response time. With this study we provide a framework which, under several assumptions, allows for a fundamental comparison of the ice-dynamic behavior across different scales. It proves to be useful in the design of conceptual numerical model setups and could also be helpful for designing laboratory glacier experiments. The concept might also be applied to real-world systems, e.g., to examine the response times of glaciers, ice streams or ice sheets to climatic perturbations.
Y1  - 2016
U6  - https://doi.org/10.5194/tc-10-1753-2016
SN  - 1994-0416
SN  - 1994-0424
VL  - 10
SP  - 1753
EP  - 1769
PB  - Copernicus
CY  - Göttingen
ER  - 
TY  - JOUR
A1  - Fischer, Jost Leonhardt
A1  - Bader, Rolf
A1  - Abel, Markus
T1  - Aeroacoustical coupling and synchronization of organ pipes
JF  - The journal of the Acoustical Society of America
N2  - A synchronization experiment on two mutual interacting organ pipes is compared with a theoretical model which takes into account the coupling mechanisms by the underlying first principles of fluid mechanics and aeroacoustics. The focus is on the Arnold-tongue, a mathematical object in the parameter space of detuning and coupling strength which quantitatively captures the interaction of the synchronized sound sources. From the experiment, a nonlinearly shaped Arnold-tongue is obtained, describing the coupling of the synchronized pipe-pipe system. This is in contrast to the linear shaped Arnold-tongue found in a preliminary experiment of the coupled system pipe-loudspeaker. To understand the experimental result, a coarse-grained model of two nonlinear coupled self-sustained oscillators is developed. The model, integrated numerically, is in very good agreement with the synchronization experiment for separation distances of the pipes in the far field and in the intermediate field. The methods introduced open the door for a deeper understanding of the fundamental processes of sound generation and the coupling mechanisms on mutual interacting acoustic oscillators. (C) 2016 Acoustical Society of America.
Y1  - 2016
U6  - https://doi.org/10.1121/1.4964135
SN  - 0001-4966
SN  - 1520-8524
VL  - 140
SP  - 2344
EP  - 2351
PB  - American Institute of Physics
CY  - Melville
ER  - 
TY  - THES
A1  - Fournier, Yori
T1  - Dynamics of the rise of magnetic flux tubes in stellar interiors
BT  - a numerical study of compressible non-axisymmetric flux tubes
N2  - In sonnenähnlichen Sternen erhält ein Dynamo-Mechanismus die Magnetfelder. Der Babcock-Leighton-Dynamo beruht auf einem solchen Mechanismus und erfordert insbesondere die Existenz von magnetischen Flussröhren. Man nimmt an, dass magnetische Flussröhren am Boden der Konvetionszone entstehen und durch Auftrieb bis zur Oberfläche steigen. Es wird ein spezielles Dynamomodell vorgeschlagen, in dem der Verzögerungseffekt durch das Aufsteigen der Flussröhren berücksichtigt wird.

Die vorliegende Dissertation beschäftigt sich mit der Anwendbarkeit des Babcock-Leighton-Dynamos auf andere Sterne. Zu diesem Zweck versuchen wir, die Aufstiegszeiten von magnetischen Flussröhren mit Hilfe von kompressiblen MHD-Simulationen in spärischen Kugelschalen mit Dichteschichtung zu bestimmen und einzugrenzen.

Derartige Simulationen sind allerdings nur in einem unrealistischen Parameterbereich möglich. Deshalb ist eine Skalierungsrelation nötig, die die Ergebnisse auf realistische physikalische Regimes überträgt. Wir erweitern frühere Arbeiten zu Skalierungsrelationen in 2D und leiten ein allgemeines Skalierungsgesetz ab, das für 2D- und 3D-Flussröhren gültig ist. In einem umfangreichen Satz von numerischen Simulationen zeigen wir, dass die abgeleitete Skalierungsrelation auch im vollständig nichtlinearen Fall gilt. Wir haben damit ein Gesetz für die Aufstiegszeit von magnetischen Flussröhren gefunden, dass in jedem sonnenähnlichen Stern Gültigkeit hat. Schließlich implementieren wir dieses Gesetz in einem Dynamomodell mit
Verzögerungsterm.

Die Simulationen eines solchen verzögerten Flussröhren/Babcock-Leighton-Dynamos auf der Basis der Meanfield-Formulierung führten auf ein neues Dynamo-Regime, das nur bei Anwesenheit der Verzögerung existiert. Die erforderlichen Verzögerungen sind von der Gröÿenordnung der Zykluslänge, die resultierenden Magnetfelder sind schwächer als die Äquipartitions-Feldstärke. Dieses neue Regime zeigt, dass auch bei sehr langen Aufstiegszeiten der Flussröhren/Babcock-Leighton-Dynamo noch nichtzerfallende Lösungen liefern und daher auf ein breites Spektrum von Sternen anwendbar sein kann.
N2  - Solar-like stars maintain their magnetic fields thanks to a dynamo mechanism. The Babcock-Leighton dynamo is one possible dynamo that has the particularity to require magnetic flux tubes. Magnetic flux tubes are assumed to form at the bottom of the convective zone and rise buoyantly to the surface. A delayed dynamo model has been suggested, where the delay accounts for the rise time of the magnetic flux tubes; a time, that has been ignored by former studies.

The present thesis aims to study the applicability of the flux tube/Babcock-Leighton dynamo to other stars. To do so, we attempt to constrain the rise time of magnetic flux tubes thanks to the first fully compressible MHD simulations of rising magnetic flux tubes in stratified rotating spherical shells.

Such simulations are limited to an unrealistic parameter space, therefore, a scaling relation is required to scale the results to realistic physical regimes. We extended earlier works on 2D scaling relations and derived a general scaling law valid for both 2D and 3D. We then carried out two large series of numerical experiments and verified that the scaling law we have derived indeed applies to the fully non-linear case. It allowed us to extract a constraint for the rise time of magnetic flux tubes that is valid for any solar-like star. We finally introduced this constraint to a delayed dynamo model.

By carrying out simulations of a mean-field, delayed, flux tube/Babcock-Leighton dynamo, we were able to identify a new dynamo regime resulting from the delay. This regime requires delays about an entire cycle and exhibits subequipartition magnetic activity. Revealing this new regime shows that even for long delays the flux tube/Babcock-Leighton dynamo can still deliver non-decaying solutions and remains a good candidate for a wide range of solar-like stars.
KW  - astrophysics
KW  - stellar physics
KW  - magnetohydrodynamics (MHD)
KW  - numerical experiments
KW  - magnetic flux tubes
KW  - dynamo theory
Y1  - 2016
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-394533
ER  - 
TY  - JOUR
A1  - Frieler, Katja
A1  - Mengel, M.
A1  - Levermann, Anders
T1  - Delaying future sea-level rise by storing water in Antarctica
JF  - Earth system dynamics
N2  - Even if greenhouse gas emissions were stopped today, sea level would continue to rise for centuries, with the long-term sea-level commitment of a 2 degrees C warmer world significantly exceeding 2 m. In view of the potential implications for coastal populations and ecosystems worldwide, we investigate, from an ice-dynamic perspective, the possibility of delaying sea-level rise by pumping ocean water onto the surface of the Antarctic ice sheet. We find that due to wave propagation ice is discharged much faster back into the ocean than would be expected from a pure advection with surface velocities. The delay time depends strongly on the distance from the coastline at which the additional mass is placed and less strongly on the rate of sea-level rise that is mitigated. A millennium-scale storage of at least 80% of the additional ice requires placing it at a distance of at least 700 km from the coastline. The pumping energy required to elevate the potential energy of ocean water to mitigate the currently observed 3 mmyr(-1) will exceed 7% of the current global primary energy supply. At the same time, the approach offers a comprehensive protection for entire coastlines particularly including regions that cannot be protected by dikes.
Y1  - 2016
U6  - https://doi.org/10.5194/esd-7-203-2016
SN  - 2190-4979
SN  - 2190-4987
VL  - 7
SP  - 203
EP  - 210
PB  - Copernicus
CY  - Göttingen
ER  - 
TY  - JOUR
A1  - Ganopolski, A.
A1  - Winkelmann, Ricarda
A1  - Schellnhuber, Hans Joachim
T1  - Critical insolation-CO2 relation for diagnosing past and future glacial inception
JF  - Nature : the international weekly journal of science
N2  - The past rapid growth of Northern Hemisphere continental ice sheets, which terminated warm and stable climate periods, is generally attributed to reduced summer insolation in boreal latitudes(1-3). Yet such summer insolation is near to its minimum at present(4), and there are no signs of a new ice age(5). This challenges our understanding of the mechanisms driving glacial cycles and our ability to predict the next glacial inception(6). Here we propose a critical functional relationship between boreal summer insolation and global carbon dioxide (CO2) concentration, which explains the beginning of the past eight glacial cycles and might anticipate future periods of glacial inception. Using an ensemble of simulations generated by an Earth system model of intermediate complexity constrained by palaeoclimatic data, we suggest that glacial inception was narrowly missed before the beginning of the Industrial Revolution. The missed inception can be accounted for by the combined effect of relatively high late-Holocene CO2 concentrations and the low orbital eccentricity of the Earth(7). Additionally, our analysis suggests that even in the absence of human perturbations no substantial build-up of ice sheets would occur within the next several thousand years and that the current interglacial would probably last for another 50,000 years. However, moderate anthropogenic cumulative CO2 emissions of 1,000 to 1,500 gigatonnes of carbon will postpone the next glacial inception by at least 100,000 years(8,9). Our simulations demonstrate that under natural conditions alone the Earth system would be expected to remain in the present delicately balanced interglacial climate state, steering clear of both large-scale glaciation of the Northern Hemisphere and its complete deglaciation, for an unusually long time.
Y1  - 2016
U6  - https://doi.org/10.1038/nature16494
SN  - 0028-0836
SN  - 1476-4687
VL  - 529
SP  - 200
EP  - U159
PB  - Nature Publ. Group
CY  - London
ER  - 
TY  - JOUR
A1  - Ge, J. X.
A1  - He, J. H.
A1  - Yan, Huirong
T1  - Effects of turbulent dust grain motion to interstellar chemistry
JF  - Monthly notices of the Royal Astronomical Society
N2  - Theoretical studies have revealed that dust grains are usually moving fast through the turbulent interstellar gas, which could have significant effects upon interstellar chemistry by modifying grain accretion. This effect is investigated in this work on the basis of numerical gas-grain chemical modelling. Major features of the grain motion effect in the typical environment of dark clouds (DC) can be summarized as follows: (1) decrease of gas-phase (both neutral and ionic) abundances and increase of surface abundances by up to 2-3 orders of magnitude; (2) shifts of the existing chemical jumps to earlier evolution ages for gas-phase species and to later ages for surface species by factors of about 10; (3) a few exceptional cases in which some species turn out to be insensitive to this effect and some other species can show opposite behaviours too. These effects usually begin to emerge from a typical DC model age of about 10(5) yr. The grain motion in a typical cold neutral medium (CNM) can help overcome the Coulomb repulsive barrier to enable effective accretion of cations on to positively charged grains. As a result, the grain motion greatly enhances the abundances of some gas-phase and surface species by factors up to 2-6 or more orders of magnitude in the CNM model. The grain motion effect in a typical molecular cloud (MC) is intermediate between that of the DC and CNM models, but with weaker strength. The grain motion is found to be important to consider in chemical simulations of typical interstellar medium.
KW  - astrochemistry
KW  - turbulence
KW  - ISM: abundances
KW  - ISM: clouds
KW  - dust, extinction
KW  - ISM: molecules
Y1  - 2016
U6  - https://doi.org/10.1093/mnras/stv2560
SN  - 0035-8711
SN  - 1365-2966
VL  - 455
SP  - 3570
EP  - 3587
PB  - Oxford Univ. Press
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Geiger, Tobias
A1  - Frieler, Katja
A1  - Levermann, Anders
T1  - High-income does not protect against hurricane losses
JF  - Environmental research letters
N2  - Damage due to tropical cyclones accounts for more than 50% of all meteorologically-induced economic losses worldwide. Their nominal impact is projected to increase substantially as the exposed population grows, per capita income increases, and anthropogenic climate change manifests. So far, historical losses due to tropical cyclones have been found to increase less than linearly with a nation's affected gross domestic product (GDP). Here we show that for the United States this scaling is caused by a sub-linear increase with affected population while relative losses scale super-linearly with per capita income. The finding is robust across a multitude of empirically derived damage models that link the storm's wind speed, exposed population, and per capita GDP to reported losses. The separation of both socio-economic predictors strongly affects the projection of potential future hurricane losses. Separating the effects of growth in population and per-capita income, per hurricane losses with respect to national GDP are projected to triple by the end of the century under unmitigated climate change, while they are estimated to decrease slightly without the separation.
KW  - climate change
KW  - tropical cyclones
KW  - damage
KW  - meteorological extremes
KW  - vulnerability
Y1  - 2016
U6  - https://doi.org/10.1088/1748-9326/11/8/084012
SN  - 1748-9326
VL  - 11
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Gessner, Oliver
A1  - Gühr, Markus
T1  - Monitoring Ultrafast Chemical Dynamics by Time-Domain X-ray Photo- and Auger-Electron Spectroscopy
JF  - Accounts of chemical research
N2  - The directed flow of charge and energy is at the heart of all chemical processes. Extraordinary efforts are underway to monitor and understand the concerted motion of electrons and nuclei with ever increasing spatial and temporal sensitivity. The element specificity, chemical sensitivity, and temporal resolution of ultrafast X-ray spectroscopy techniques hold great promise to provide new insight into the fundamental interactions underlying chemical dynamics in systems ranging from isolated molecules to application-like devices. Here, we focus on the potential of ultrafast X-ray spectroscopy techniques based on the detection of photo- and Auger electrons to provide new fundamental insight into photochemical processes of systems with various degrees of complexity. Isolated nucleobases provide an excellent testing ground for our most fundamental understanding of intramolecular coupling between electrons and nuclei beyond the traditionally applied Born-Oppenheimer approximation. Ultrafast electronic relaxation dynamics enabled by the breakdown of this approximation is the major component of the nucleobase photoprotection mechanisms. Transient X-ray induced Auger electron spectroscopy on photoexcited thymine molecules provides atomic-site specific details of the extremely efficient coupling that converts potentially bond changing ultraviolet photon energy into benign heat. In particular, the time-dependent spectral shift of a specific Auger band is sensitive to the length of a single bond within the molecule. The X-ray induced Auger transients show evidence for an electronic transition out of the initially excited state within only similar to 200 fs in contrast to theoretically predicted picosecond population trapping behind a reaction barrier. Photoinduced charge transfer dynamics between transition metal complexes and semiconductor nanostructures are of central importance for many emerging energy and climate relevant technologies. Numerous demonstrations of photovoltaic and photocatalytic activity have been performed based on the combination of strong light absorption in dye molecules with charge separation and transport in adjacent semiconductor nanostructures. However, a fundamental understanding of the enabling and limiting dynamics on critical atomic length- and time scales is often still lacking. Femtosecond time-resolved X-ray photoelectron spectroscopy is employed to gain a better understanding of a short-lived intermediate that may be linked to the unexpectedly limited performance of ZnO based dye-sensitized solar cells by delaying the generation of free charge carriers. The transient spectra strongly suggest that photoexcited dye molecules attached to ZnO nanocrystals inject their charges into the substrate within less than 1 ps but the electrons are then temporarily trapped at the surface of the semiconductor in direct vicinity of the injecting molecules. The experiments are extended to monitor the electronic response of the semiconductor substrate to the collective injection from a monolayer of dye molecules and the subsequent electron-ion recombination dynamics. The results indicate some qualitative similarities but quantitative differences between the recombination dynamics at molecule-semiconductor interfaces and previously studied bulk-surface electron-hole recombination dynamics in photoexcited semiconductors.
Y1  - 2016
U6  - https://doi.org/10.1021/acs.accounts.5b00361
SN  - 0001-4842
SN  - 1520-4898
VL  - 49
SP  - 138
EP  - 145
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Ghosh, Surya K.
A1  - Cherstvy, Andrey G.
A1  - Grebenkov, Denis S.
A1  - Metzler, Ralf
T1  - Anomalous, non-Gaussian tracer diffusion in crowded two-dimensional environments
JF  - NEW JOURNAL OF PHYSICS
N2  - A topic of intense current investigation pursues the question of how the highly crowded environment of biological cells affects the dynamic properties of passively diffusing particles. Motivated by recent experiments we report results of extensive simulations of the motion of a finite sized tracer particle in a heterogeneously crowded environment made up of quenched distributions of monodisperse crowders of varying sizes in finite circular two-dimensional domains. For given spatial distributions of monodisperse crowders we demonstrate how anomalous diffusion with strongly non-Gaussian features arises in this model system. We investigate both biologically relevant situations of particles released either at the surface of an inner domain or at the outer boundary, exhibiting distinctly different features of the observed anomalous diffusion for heterogeneous distributions of crowders. Specifically we reveal an asymmetric spreading of tracers even at moderate crowding. In addition to the mean squared displacement (MSD) and local diffusion exponent we investigate the magnitude and the amplitude scatter of the time averaged MSD of individual tracer trajectories, the non-Gaussianity parameter, and the van Hove correlation function. We also quantify how the average tracer diffusivity varies with the position in the domain with a heterogeneous radial distribution of crowders and examine the behaviour of the survival probability and the dynamics of the tracer survival probability. Inter alia, the systems we investigate are related to the passive transport of lipid molecules and proteins in two-dimensional crowded membranes or the motion in colloidal solutions or emulsions in effectively two-dimensional geometries, as well as inside supercrowded, surface adhered cells.
KW  - anomalous diffusion
KW  - crowded fluids
KW  - stochastic processes
Y1  - 2016
U6  - https://doi.org/10.1088/1367-2630/18/1/013027
SN  - 1367-2630
VL  - 18
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Ghosh, Surya K.
A1  - Cherstvy, Andrey G.
A1  - Petrov, Eugene P.
A1  - Metzler, Ralf
T1  - Interactions of rod-like particles on responsive elastic sheets
JF  - Soft matter
N2  - What are the physical laws of the mutual interactions of objects bound to cell membranes, such as various membrane proteins or elongated virus particles? To rationalise this, we here investigate by extensive computer simulations mutual interactions of rod-like particles adsorbed on the surface of responsive elastic two-dimensional sheets. Specifically, we quantify sheet deformations as a response to adhesion of such filamentous particles. We demonstrate that tip-to-tip contacts of rods are favoured for relatively soft sheets, while side-by-side contacts are preferred for stiffer elastic substrates. These attractive orientation-dependent substrate-mediated interactions between the rod-like particles on responsive sheets can drive their aggregation and self-assembly. The optimal orientation of the membrane-bound rods is established via responding to the elastic energy profiles created around the particles. We unveil the phase diagramme of attractive–repulsive rod–rod interactions in the plane of their separation and mutual orientation. Applications of our results to other systems featuring membrane-associated particles are also discussed.
Y1  - 2016
U6  - https://doi.org/10.1039/C6SM01522K
SN  - 1744-6848
SN  - 1744-683X
PB  - RSC
CY  - London
ER  - 
TY  - GEN
A1  - Ghosh, Surya K.
A1  - Cherstvy, Andrey G.
A1  - Petrov, Eugene P.
A1  - Metzler, Ralf
T1  - Interactions of rod-like particles on responsive elastic sheets
N2  - What are the physical laws of the mutual interactions of objects bound to cell membranes, such as various membrane proteins or elongated virus particles? To rationalise this, we here investigate by extensive computer simulations mutual interactions of rod-like particles adsorbed on the surface of responsive elastic two-dimensional sheets. Specifically, we quantify sheet deformations as a response to adhesion of such filamentous particles. We demonstrate that tip-to-tip contacts of rods are favoured for relatively soft sheets, while side-by-side contacts are preferred for stiffer elastic substrates. These attractive orientation-dependent substrate-mediated interactions between the rod-like particles on responsive sheets can drive their aggregation and self-assembly. The optimal orientation of the membrane-bound rods is established via responding to the elastic energy profiles created around the particles. We unveil the phase diagramme of attractive–repulsive rod–rod interactions in the plane of their separation and mutual orientation. Applications of our results to other systems featuring membrane-associated particles are also discussed.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 256 
Y1  - 2016
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-95882
ER  - 
TY  - JOUR
A1  - Ghosh, Surya K.
A1  - Cherstvy, Andrey G.
A1  - Petrov, Eugene P.
A1  - Metzler, Ralf
T1  - Interactions of rod-like particles on responsive elastic sheets
JF  - Soft matter
N2  - What are the physical laws of the mutual interactions of objects bound to cell membranes, such as various membrane proteins or elongated virus particles? To rationalise this, we here investigate by extensive computer simulations mutual interactions of rod-like particles adsorbed on the surface of responsive elastic two-dimensional sheets. Specifically, we quantify sheet deformations as a response to adhesion of such filamentous particles. We demonstrate that tip-to-tip contacts of rods are favoured for relatively soft sheets, while side-by-side contacts are preferred for stiffer elastic substrates. These attractive orientation-dependent substrate-mediated interactions between the rod-like particles on responsive sheets can drive their aggregation and self-assembly. The optimal orientation of the membrane-bound rods is established via responding to the elastic energy profiles created around the particles. We unveil the phase diagramme of attractive-repulsive rod-rod interactions in the plane of their separation and mutual orientation. Applications of our results to other systems featuring membrane-associated particles are also discussed.
Y1  - 2016
U6  - https://doi.org/10.1039/c6sm01522k
SN  - 1744-683X
SN  - 1744-6848
VL  - 12
SP  - 7908
EP  - 7919
PB  - Royal Society of Chemistry
CY  - Cambridge
ER  - 
TY  - JOUR
A1  - Gimenez-Garcia, Ana
A1  - Shenar, Tomer
A1  - Torrejon, J. M.
A1  - Oskinova, Lida
A1  - Martinez-Nunez, S.
A1  - Hamann, Wolf-Rainer
A1  - Rodes-Roca, J. J.
A1  - González-Galan, A.
A1  - Alonso-Santiago, J.
A1  - González-Fernández, C.
A1  - Bernabeu, Guillermo
A1  - Sander, Andreas Alexander Christoph
T1  - Measuring the stellar wind parameters in IGR J17544-2619 and Vela X-1 constrains the accretion physics in supergiant fast X-ray transient and classical supergiant X-ray binaries
JF  - Siberian Mathematical Journal
N2  - Aims. To close this gap, we perform a comparative analysis of the optical companion in two important systems: IGR J175442619 (SFXT) and Vela X-1 (SGXB). We analyze the spectra of each star in detail and derive their stellar and wind properties. As a next step, we compare the wind parameters, giving us an excellent chance of recognizing key differences between donor winds in SFXTs and SGXBs. Methods. We use archival infrared, optical and ultraviolet observations, and analyze them with the non-local thermodynamic equilibrium (NLTE) Potsdam Wolf-Rayet model atmosphere code. We derive the physical properties of the stars and their stellar winds, accounting for the influence of X-rays on the stellar winds. Results. We find that the stellar parameters derived from the analysis generally agree well with the spectral types of the two donors: O9I (IGR J17544-2619) and B0.5Iae (Vela X-1). The distance to the sources have been revised and also agree well with the estimations already available in the literature. In IGR J17544-2619 we are able to narrow the uncertainty to d = 3.0 +/- 0.2 kpc. From the stellar radius of the donor and its X-ray behavior, the eccentricity of IGR J17544-2619 is constrained to e < 0.25. The derived chemical abundances point to certain mixing during the lifetime of the donors. An important difference between the stellar winds of the two stars is their terminal velocities (v(infinity) = 1500 km s(-1) in IGR J17544-2619 and v(infinity) = 700 km s(-1) in Vela X-1), which have important consequences on the X-ray luminosity of these sources. Conclusions. The donors of IGR J17544-2619 and Vela X-1 have similar spectral types as well as similar parameters that physically characterize them and their spectra. In addition, the orbital parameters of the systems are similar too, with a nearly circular orbit and short orbital period. However, they show moderate differences in their stellar wind velocity and the spin period of their neutron star which has a strong impact on the X-ray luminosity of the sources. This specific combination of wind speed and pulsar spin favors an accretion regime with a persistently high luminosity in Vela X-1, while it favors an inhibiting accretion mechanism in IGR J17544-2619. Our study demonstrates that the relative wind velocity is critical in class determination for the HMXBs hosting a supergiant donor, given that it may shift the accretion mechanism from direct accretion to propeller regimes when combined with other parameters.
KW  - accretion, accretion disks
KW  - methods: observational
KW  - techniques: spectroscopic
KW  - stars: atmospheres
KW  - X-rays: binaries
KW  - stars: winds, outflows
Y1  - 2016
U6  - https://doi.org/10.1051/0004-6361/201527551
SN  - 1432-0746
VL  - 591
PB  - EDP Sciences
CY  - Les Ulis
ER  - 
TY  - JOUR
A1  - Godec, Aljaz
A1  - Metzler, Ralf
T1  - First passage time distribution in heterogeneity controlled kinetics: going beyond the mean first passage time
JF  - Scientific reports
N2  - The first passage is a generic concept for quantifying when a random quantity such as the position of a diffusing molecule or the value of a stock crosses a preset threshold (target) for the first time. The last decade saw an enlightening series of new results focusing mostly on the so-called mean and global first passage time (MFPT and GFPT, respectively) of such processes. Here we push the understanding of first passage processes one step further. For a simple heterogeneous system we derive rigorously the complete distribution of first passage times (FPTs). Our results demonstrate that the typical FPT significantly differs from the MFPT, which corresponds to the long time behaviour of the FPT distribution. Conversely, the short time behaviour is shown to correspond to trajectories connecting directly from the initial value to the target. Remarkably, we reveal a previously overlooked third characteristic time scale of the first passage dynamics mirroring brief excursion away from the target.
Y1  - 2016
U6  - https://doi.org/10.1038/srep20349
SN  - 2045-2322
VL  - 6
PB  - Nature Publ. Group
CY  - London
ER  - 
TY  - JOUR
A1  - Godec, Aljaz
A1  - Metzler, Ralf
T1  - Universal Proximity Effect in Target Search Kinetics in the
Few-Encounter Limit
JF  - Physical review : X, Expanding access
N2  - When does a diffusing particle reach its target for the first time? This first-passage time (FPT) problem is central to the kinetics of molecular reactions in chemistry and molecular biology. Here, we explain the behavior of smooth FPT densities, for which all moments are finite, and demonstrate universal yet generally non-Poissonian long-time asymptotics for a broad variety of transport processes. While Poisson-like asymptotics arise generically in the presence of an effective repulsion in the immediate vicinity of the target, a time-scale separation between direct and reflected indirect trajectories gives rise to a universal proximity effect: Direct paths, heading more or less straight from the point of release to the target, become typical and focused, with a narrow spread of the corresponding first-passage times. Conversely, statistically dominant indirect paths exploring the entire system tend to be massively dissimilar. The initial distance to the target particularly impacts gene regulatory or competitive stochastic processes, for which few binding events often determine the regulatory outcome. The proximity effect is independent of details of the transport, highlighting the robust character of the FPT features uncovered here.
Y1  - 2016
U6  - https://doi.org/10.1103/PhysRevX.6.041037
SN  - 2160-3308
VL  - 6
PB  - American Physical Society
CY  - College Park
ER  - 
TY  - JOUR
A1  - Godec, Aljaz
A1  - Metzler, Ralf
T1  - Active transport improves the precision of linear long distance molecular signalling
JF  - Journal of physics : A, Mathematical and theoretical
N2  - Molecular signalling in living cells occurs at low copy numbers and is thereby inherently limited by the noise imposed by thermal diffusion. The precision at which biochemical receptors can count signalling molecules is intimately related to the noise correlation time. In addition to passive thermal diffusion, messenger RNA and vesicle-engulfed signalling molecules can transiently bind to molecular motors and are actively transported across biological cells. Active transport is most beneficial when trafficking occurs over large distances, for instance up to the order of 1 metre in neurons. Here we explain how intermittent active transport allows for faster equilibration upon a change in concentration triggered by biochemical stimuli. Moreover, we show how intermittent active excursions induce qualitative changes in the noise in effectively one-dimensional systems such as dendrites. Thereby they allow for significantly improved signalling precision in the sense of a smaller relative deviation in the concentration read-out by the receptor. On the basis of linear response theory we derive the exact mean field precision limit for counting actively transported molecules. We explain how intermittent active excursions disrupt the recurrence in the molecular motion, thereby facilitating improved signalling accuracy. Our results provide a deeper understanding of how recurrence affects molecular signalling precision in biological cells and novel medical-diagnostic devices.
KW  - noise in biochemical signalling
KW  - Brownian motion
KW  - active transport
KW  - linear response theory
KW  - fluctuation-dissipation theorem
KW  - generalised Langevin equation
KW  - recurrence
Y1  - 2016
U6  - https://doi.org/10.1088/1751-8113/49/36/364001
SN  - 1751-8113
SN  - 1751-8121
VL  - 49
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - THES
A1  - Gomez, David
T1  - Mechanisms of biochemical reactions within crowded environments
T1  - Mechanismus der Biochemische Reaktionen im vollgestopfte Umgebungen
N2  - The cell interior is a highly packed environment in which biological macromolecules evolve and function. This crowded media has effects in many biological processes such as protein-protein binding, gene regulation, and protein folding. Thus, biochemical reactions that take place in such crowded conditions differ from diluted test tube conditions, and a considerable effort has been invested in order to understand such differences.
In this work, we combine different computationally tools to disentangle the effects of molecular crowding on biochemical processes. First, we propose a lattice model to study the implications of molecular crowding on enzymatic reactions. We provide a detailed picture of how crowding affects binding and unbinding events and how the separate effects of crowding on binding equilibrium act together. Then, we implement a lattice model to study the effects of molecular crowding on facilitated diffusion. We find that obstacles on the DNA impair facilitated diffusion. However, the extent of this effect depends on how dynamic obstacles are on the DNA. For the scenario in which crowders are only present in the bulk solution, we find that at some conditions presence of crowding agents can enhance specific-DNA binding. Finally, we make use of structure-based techniques to look at the impact of the presence of crowders on the folding a protein. We find that polymeric crowders have stronger effects on protein stability than spherical crowders. The strength of this effect increases as the polymeric crowders become longer. The methods we propose here are general and can also be applied to more complicated systems.
N2  - Innerhalb einer Zelle, im Zytosol, entstehen und arbeiten sehr viele biologische Makromoleküle. Die Dichte dieser Moleküle ist sehr hoch und dieses ‘vollgestopfte’ Zytosol hat vielfältige Auswirkungen auf viele biologische Prozessen wie zum Beispiel Protein-Protein Interaktionen, Genregulation oder die Faltung von Proteinen. Der Ablauf von vielen biochemische Reaktionen in dieser Umgebung weicht von denen unter verdünnte Laborbedingungen ab. Um die Effekte dieses ‘makromolekularen Crowdings’ zu verstehen, wurde in den letzten Jahren bereits viel Mühe investiert.
In dieser Arbeit kombinieren wir verschiede Computermethoden, um die Wirkungen des ‘makromolekularen Crowdings’ auf biologische Prozesse besser zu  verstehen. Zuerst schlagen wir ein Gittermodell vor, um damit die Effekte des ‘makromolekularen Crowdings’ auf enzymatische Reaktionen zu studieren. Damit stellen wir ein detailliertes Bild zusammen, wie Crowding die Assoziations- und Dissozotationsraten beeinflusst und wie verschiedene crowding-Effekte zusammen auf die Gleichgewichtskonstante wirken.
Weiterhin implementieren wir ein Gittermodell der ‘erleichterte Diffusion’. Unsere Ergebnisse zeigen, dass Hindernisse an der DNA die vereinfachte Diffusion beeinträchtigen. Das Ausmass dieser Wirkung hängt dabei von der Dynamik der Hindernisse an der DNA ab. Im dem Fall dass Crowder ausschließlich in der Lösung vorhanden sind, erhöhen sich unter bestimmten Bedingungen DNA-spezifische Bindungen.
Schließlich nutzten wir strukturbasierte Techniken um damit die Auswirkungen von Crowding auf die Faltung von Proteinen zu untersuchen. Wir fanden dabei, dass Polymer Crowder stärkere Wirkungen auf die Proteinstabilität haben als kugelförmige Crowder. Dieser Effekt verstärkte sich mit der Länge der untersuchten Polymere. Die Methoden die hier vorgeschlagen werden, sind generell anwendbar und können auch an deutlich komplexeren Systemen angewandt werden.
KW  - molecular crowding
KW  - gene expression
KW  - enzymatic activity
KW  - protein folding
KW  - Molecular crowding
KW  - enzymatische Reaktionen
KW  - Genregulation
KW  - Faltung von Proteinen
Y1  - 2016
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-94593
ER  - 
TY  - JOUR
A1  - Gonzalez Manrique, Sergio Javier
A1  - Kuckein, Christoph
A1  - Pastor Yabar, A.
A1  - Collados Vera, M.
A1  - Denker, Carsten
A1  - Fischer, C. E.
A1  - Gömöry, P.
A1  - Diercke, Andrea
A1  - Gonzalez, N. Bello
A1  - Schlichenmaier, R.
A1  - Balthasar, H.
A1  - Berkefeld, T.
A1  - Feller, A.
A1  - Hoch, S.
A1  - Hofmann, A.
A1  - Kneer, F.
A1  - Lagg, A.
A1  - Nicklas, H.
A1  - Orozco Suarez, D.
A1  - Schmidt, D.
A1  - Schmidt, W.
A1  - Sigwarth, M.
A1  - Sobotka, M.
A1  - Solanki, S. K.
A1  - Soltau, D.
A1  - Staude, J.
A1  - Strassmeier, Klaus G.
A1  - Verma, Meetu
A1  - Volkmer, R.
A1  - von der Lühe, O.
A1  - Waldmann, T.
T1  - Fitting peculiar spectral profiles in He I 10830 angstrom absorption features
JF  - Astronomische Nachrichten = Astronomical notes
N2  - The new generation of solar instruments provides better spectral, spatial, and temporal resolution for a better understanding of the physical processes that take place on the Sun. Multiple-component profiles are more commonly observed with these instruments. Particularly, the He i 10830 triplet presents such peculiar spectral profiles, which give information on the velocity and magnetic fine structure of the upper chromosphere. The purpose of this investigation is to describe a technique to efficiently fit the two blended components of the He i 10830 triplet, which are commonly observed when two atmospheric components are located within the same resolution element. The observations used in this study were taken on 2015 April 17 with the very fast spectroscopic mode of the GREGOR Infrared Spectrograph (GRIS) attached to the 1.5-m GREGOR solar telescope, located at the Observatorio del Teide, Tenerife, Spain. We apply a double-Lorentzian fitting technique using Levenberg-Marquardt least-squares minimization. This technique is very simple and much faster than inversion codes. Line-of-sight Doppler velocities can be inferred for a whole map of pixels within just a few minutes. Our results show sub-and supersonic downflow velocities of up to 32 km s(-1) for the fast component in the vicinity of footpoints of filamentary structures. The slow component presents velocities close to rest. (C) 2016 WILEY-VCH Verlag GmbH& Co. KGaA, Weinheim
KW  - Sun: chromosphere
KW  - methods: data analysis
KW  - techniques: spectroscopic
KW  - line: profiles
Y1  - 2016
U6  - https://doi.org/10.1002/asna.201512433
SN  - 0004-6337
SN  - 1521-3994
VL  - 337
SP  - 1057
EP  - 1063
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - GEN
A1  - Goychuk, Igor
T1  - Quantum ergodicity breaking in semi-classical electron transfer dynamics
N2  - Can the statistical properties of single-electron transfer events be correctly predicted within a common equilibrium ensemble description? This fundamental in nanoworld question of ergodic behavior is scrutinized within a very basic semi-classical curve-crossing problem. It is shown that in the limit of non-adiabatic electron transfer (weak tunneling) well-described by the Marcus–Levich–Dogonadze(MLD) rate the answer is yes. However, in the limit of the so-called solvent-controlled adiabatic electron transfer, a profound breaking of ergodicity occurs. Namely, a common description based on the ensemble reduced density matrix with an initial equilibrium distribution of the reaction coordinate is not able to reproduce the statistics of single-trajectory events in this seemingly classical regime. For sufficiently large activation barriers, the ensemble survival probability in a state remains nearly exponential with the inverse rate given by the sum of the adiabatic curve crossing (Kramers) time and the inverse MLD rate. In contrast, near to the adiabatic regime, the single-electron survival probability is clearly non-exponential, even though it possesses an exponential tail which agrees well with the ensemble description. Initially, it is well described by a Mittag-Leffler distribution with a fractional rate. Paradoxically, the mean transfer time in this classical on the ensemble level regime is well described by the inverse of the nonadiabatic quantum tunneling rate on a single particle level. An analytical theory is developed which perfectly agrees with stochastic simulations and explains our findings.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 299 
Y1  - 2016
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-102264
ER  - 
TY  - JOUR
A1  - Goychuk, Igor
T1  - Molecular machines operating on the nanoscale: from classical to quantum
JF  - Beilstein journal of nanotechnology
N2  - The main physical features and operating principles of isothermal nanomachines in the microworld, common to both classical and quantum machines, are reviewed. Special attention is paid to the dual, constructive role of dissipation and thermal fluctuations, the fluctuation-dissipation theorem, heat losses and free energy transduction, thermodynamic efficiency, and thermodynamic efficiency at maximum power. Several basic models are considered and discussed to highlight generic physical features. This work examines some common fallacies that continue to plague the literature. In particular, the erroneous beliefs that one should minimize friction and lower the temperature for high performance of Brownian machines, and that the thermodynamic efficiency at maximum power cannot exceed one-half are discussed. The emerging topic of anomalous molecular motors operating subdiffusively but very efficiently in the viscoelastic environment of living cells is also discussed.
KW  - anomalous dynamics with memory
KW  - Brownian nanomachines
KW  - nanoscale friction and thermal noise
KW  - quantum effects
KW  - thermodynamic efficiency
Y1  - 2016
U6  - https://doi.org/10.3762/bjnano.7.31
SN  - 2190-4286
VL  - 7
SP  - 328
EP  - 350
PB  - Beilstein-Institut zur Förderung der Chemischen Wissenschaften
CY  - Frankfurt, Main
ER  - 
TY  - JOUR
A1  - Guber, Christoph R.
A1  - Richter, Philipp
T1  - Dust depletion of Ca and Ti in QSO absorption-line systems
JF  - Wiley Interdisciplinary Reviews : Water
N2  - Aims. To explore the role of titanium-and calcium-dust depletion in gas in and around galaxies, we systematically study Ti/Ca abundance ratios in intervening absorption-line systems at low and high redshift. Methods. We investigate high-resolution optical spectra obtained by the UVES instrument at the Very Large Telescope (VLT) and spectroscopically analyze 34 absorption-line systems at z <= 0.5 to measure column densities (or limits) for Ca II and Ti II. We complement our UVES data set with previously published absorption-line data on Ti/Ca for redshifts up to z similar to 3.8. Our absorber sample contains 110 absorbers including damped Lyman alpha systems (DLAs), sub-DLAs, and Lyman-Limit systems (LLS). We compare our Ti/Ca findings with results from the MilkyWay and the Magellanic Clouds and discuss the properties of Ti/Ca absorbers in the general context of quasar absorption-line systems. Results. Our analysis indicates that there are two distinct populations of absorbers with either high or low Ti/Ca ratios with a separation at [Ti/Ca] approximate to 1. While the calcium-dust depletion in most of the absorbers appears to be severe, the titanium depletions are mild in systems with high Ti/Ca ratios. The derived trend indicates that absorbers with high Ti/Ca ratios have dust-to-gas ratios that are substantially lower than in the Milky Way. We characterize the overall nature of the absorbers by correlating Ti/Ca with other observables (e.g., metallicity, velocity-component structure) and by modeling the ionization properties of singly-ionized Ca and Ti in different environments. Conclusions. We conclude that Ca II and Ti II bearing absorption-line systems trace predominantly neutral gas in the disks and inner halo regions of galaxies, where the abundance of Ca and Ti reflects the local metal and dust content of the gas. Our study suggests that the Ti/Ca ratio represents a useful measure for the gas-to-dust ratio and overall metallicity in intervening absorption-line systems.
KW  - quasars: absorption lines
KW  - dust, extinction
KW  - galaxies: abundances
KW  - galaxies: ISM
KW  - intergalactic medium
Y1  - 2016
U6  - https://doi.org/10.1051/0004-6361/201628466
SN  - 1432-0746
VL  - 591
PB  - EDP Sciences
CY  - Les Ulis
ER  - 
TY  - GEN
A1  - Gühr, Markus
T1  - Ultrafast Soft X-ray Probing of Gas Phase Molecular Dynamics
N2  - The molecular ability to selectively and efficiently convert sunlight into other forms of energy like heat, bond change, or charge separation is truly remarkable. The decisive steps in these transformations often happen on a femtosecond timescale and require transitions among different electronic states that violate the Born-Oppenheimer approximation (BOA). Non-BOA transitions pose challenges to both theory and experiment. From a theoretical point of view, excited state dynamics and nonadiabatic transitions both are difficult problems (see Figure 1(a)). However, the theory on non-BOA dynamics has advanced significantly over the last two decades. Full dynamical simulations for molecules of the size of nucleobases have been possible for a couple of years and allow predictions of experimental observables like photoelectron energy or ion yield. The availability of these calculations for isolated molecules has spurred new experimental efforts to develop methods that are sufficiently different from all optical techniques. For determination of transient molecular structure, femtosecond X-ray diffraction and electron diffraction have been implemented on optically excited molecules.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 268 
Y1  - 2016
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-97215
ER  - 
TY  - THES
A1  - Habicht, Klaus
T1  - Neutron-resonance spin-echo spectroscopy
BT  - a high resolution look at dispersive excitations
Y1  - 2016
ER  - 
TY  - JOUR
A1  - Hahn, Tobias
A1  - Tscheuschner, Steffen
A1  - Saller, Christina
A1  - Strohriegl, Peter
A1  - Boregowda, Puttaraju
A1  - Mukhopadhyay, Tushita
A1  - Patil, Satish
A1  - Neher, Dieter
A1  - Bässler, Heinz
A1  - Köhler, Anna
T1  - Role of Intrinsic Photogeneration in Single Layer and Bilayer Solar Cells with C-60 and PCBM
JF  - The journal of physical chemistry : C, Nanomaterials and interfaces
Y1  - 2016
U6  - https://doi.org/10.1021/acs.jpcc.6b08471
SN  - 1932-7447
VL  - 120
SP  - 25083
EP  - 25091
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Hamaguchi, K.
A1  - Oskinova, Lida
A1  - Russell, C. M. P.
A1  - Petre, R.
A1  - Enoto, T.
A1  - Morihana, K.
A1  - Ishida, M.
T1  - DISCOVERY OF RAPIDLY MOVING PARTIAL X-RAY ABSORBERS WITHIN GAMMA CASSIOPEIAE
JF  - The astrophysical journal : an international review of spectroscopy and astronomical physics
N2  - detected six rapid X-ray spectral hardening events called "softness dips" in a similar to 100 ks observation in 2011. All the softness dip events show symmetric softness-ratio variations, and some of them have flat bottoms apparently due to saturation. The softness dip spectra are best described by either similar to 40% or similar to 70% partial covering absorption to kT similar to 12 keV plasma emission by matter with a neutral hydrogen column density of similar to(2-8) x 10(21) cm(-2), while the spectrum outside these dips is almost free of absorption. This result suggests the presence of two distinct X-ray-emitting spots in the.. Cas system, perhaps on a white dwarf (WD) companion with dipole mass accretion. The partial covering absorbers may be blobs in the Be stellar wind, the Be disk, or rotating around the WD companion. Weak correlations of the softness ratios to the hard X-ray flux suggest the presence of stable plasmas at kT similar to 0.9 and 5 keV, which may originate from the Be or WD winds. The formation of a Be star and WD binary system requires mass transfer between two stars; gamma Cas may have experienced such activity in the past.
KW  - blue stragglers
KW  - stars: emission-line, Be
KW  - stars: individual (gamma Cassiopeiae)
KW  - stars: winds, outflows
KW  - white dwarfs
KW  - X-rays: stars
Y1  - 2016
U6  - https://doi.org/10.3847/0004-637X/832/2/140
SN  - 0004-637X
SN  - 1538-4357
VL  - 832
SP  - 33
EP  - 49
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Hassanin, Alshaimaa
A1  - Kliem, Bernhard
A1  - Seehafer, Norbert
T1  - Helical kink instability in the confined solar eruption on 2002 May 27
JF  - Astronomische Nachrichten = Astronomical notes
KW  - instabilities
KW  - magnetohydrodynamics (MHD)
KW  - Sun: corona
KW  - Sun: coronal mass ejections (CMEs)
KW  - Sun: flares
Y1  - 2016
U6  - https://doi.org/10.1002/asna.201612446
SN  - 0004-6337
SN  - 1521-3994
VL  - 337
SP  - 1082
EP  - 1089
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - THES
A1  - Herenz, Edmund Christian
T1  - Detecting and understanding extragalactic Lyman α emission using 3D spectroscopy
T1  - Detektion und Interpretation extragalaktischer Lyman Alpha Emission mittels 3D Spektroskopie
N2  - In this thesis we use integral-field spectroscopy to detect and understand of Lyman α (Lyα) emission from high-redshift galaxies.

Intrinsically the Lyα emission at λ = 1216 Å is the strongest recombination line from galaxies.  It arises from the 2p → 1s transition in hydrogen.  In star-forming galaxies the line is powered by ionisation of the interstellar gas by hot O- and B- stars.  Galaxies with star-formation rates of 1 - 10 Msol/year are expected to have Lyα luminosities of 42 dex - 43 dex (erg/s), corresponding to fluxes ~ -17 dex - -18 dex (erg/s/cm²) at redshifts z~3, where Lyα is easily accessible with ground-based telescopes.  However, star-forming galaxies do not show these expected Lyα fluxes.  Primarily this is a consequence of the high-absorption cross-section of neutral hydrogen for Lyα photons σ ~ -14 dex (cm²).  Therefore, in typical interstellar environments Lyα photons have to undergo a complex radiative transfer.  The exact conditions under which Lyα photons can escape a galaxy are poorly understood.

Here we present results from three observational projects.  In Chapter 2, we show integral field spectroscopic observations of 14 nearby star-forming galaxies in Balmer α radiation (Hα, λ = 6562.8 Å).  These observations were obtained with the Potsdam Multi Aperture Spectrophotometer at the Calar-Alto 3.5m Telescope}.  Hα directly traces the intrinsic Lyα radiation field.  We present Hα velocity fields and velocity dispersion maps spatially registered onto Hubble Space Telescope Lyα and Hα images.  From our observations, we conjecture a causal connection between spatially resolved Hα kinematics and Lyα photometry for individual galaxies.  Statistically, we find that dispersion-dominated galaxies are more likely to emit Lyα photons than galaxies where ordered gas-motions dominate.  This result indicates that turbulence in actively star-forming systems favours an escape of Lyα radiation.

Not only massive stars can power Lyα radiation, but also non-thermal emission from an accreting super-massive black hole in the galaxy centre.  If a galaxy harbours such an active galactic nucleus, the rate of hydrogen-ionising photons can be more than 1000 times higher than that of a typical star-forming galaxy.  This radiation can potentially ionise large regions well outside the main stellar body of galaxies.  Therefore, it is expected that the neutral hydrogen from these circum-galactic regions shines fluorescently in Lyα.  Circum-galactic gas plays a crucial role in galaxy formation.  It may act as a reservoir for fuelling star formation, and it is also subject to feedback processes that expel galactic material.  If Lyα emission from this circum-galactic medium (CGM) was detected, these important processes could be studied in-situ around high-z galaxies.  In Chapter 3, we show observations of five radio-quiet quasars with PMAS to search for possible extended CGM emission in the Lyα line.  However, in four of the five objects, we find no significant traces of this emission.  In the fifth object, there is evidence for a weak and spatially quite compact Lyα excess at several kpc outside the nucleus.  The faintness of these structures is consistent with the idea that radio-quiet quasars typically reside in dark matter haloes of modest masses.  While we were not able to detect Lyα CGM emission, our upper limits provide constraints for the new generation of IFS instruments at 8--10m class telescopes.

The Multi Unit Spectroscopic Explorer (MUSE) at ESOs Very Large Telescopeis such an unique instrument.  One of the main motivating drivers in its construction was the use as a survey instrument for Lyα emitting galaxies at high-z.  Currently, we are conducting such a survey that will cover a total area of ~100 square arcminutes with 1 hour exposures for each 1 square arcminute MUSE pointing.  As a first result from this survey we present in Chapter 5 a catalogue of 831 emission-line selected galaxies from a 22.2 square arcminute region in the Chandra Deep Field South.  In order to construct the catalogue, we developed and implemented a novel source detection algorithm -- LSDCat -- based on matched filtering for line emission in 3D spectroscopic datasets (Chapter 4).  Our catalogue contains 237 Lyα emitting galaxies in the redshift range 3 ≲ z ≲ 6.  Only four of those previously had spectroscopic redshifts in the literature.  We conclude this thesis with an outlook on the construction of a Lyα luminosity function based on this unique sample (Chapter 6).
N2  - In der vorliegenden Doktorarbeit präsentieren wir Resultate aus drei integralfeldspektroskopischen Beobachtungskampagnen die mit der Intention Lyman α (Lyα) Strahlung von hoch-rotverschobenen Galaxien zu detektieren und zu verstehen durchgeführt wurden.

Die Lyα Emissionslinie im ultravioletten Teil des elektromagnetischen Spektrums (λ = 1216 Å) ist intrinsisch die stärkste Rekombinationslinie im Linienspektrum sternbildender Galaxien.  Die Linie ist eine Folge der Ionisation des interstellaren Gases durch heiße O- und B- Sterne.  Man erwartet von Galaxien mit Sternentstehungsraten 1 - 10 Msol/Jahr intrinsische Lyα Leuchtkräfte von 42 dex - 43 dex (erg/s), was bei Rotverschiebungen von z~3, bei denen Lyα mit bodengebundenen Teleskopen zu beobachten ist, einem Strahlungsstrom von ~ -17 dex - -18 dex (erg/s/cm²) entspricht.  Allerdings werden nicht von allen sternbildenen Galaxien derartige Lyα Strahlungsströme gemessen.  Dies ist in erster Linie eine direkte Konsequenz des hohen Absorptionsquerschnitts von neutralem Wasserstoff für Lyα Photonen.  Deshalb erfahren Lyα Photonen einen komplexen Strahlungstransportprozess in typischen interstellaren Umgebungen.  Die exakten Bedingungen bei denen Lyα Strahlung eine Galaxie verlassen sind noch nicht hinreichend gut verstanden.


Diesbezüglich werden in Kapitel 2 dieser Arbeit integralfeldspektroskopische Beobachtungsergebnisse der Balmer α Strahlung (Hα, λ = 6562.8 Å) von 14 nahen sternbildenden Galaxien gezeigt.  Die Beobachtungsdaten wurden mit dem Potsdam Multi Aperture Spectrophotometer (PMAS) am Calar Alto 3.5m Teleskop gewonnen.  Hα Strahlung ist eine direkte Kopie des intrinischen Lyα Strahlungsfeldes der Galaxien.  Wir zeigen unsere Hα Geschwindigkeitsfelder und Geschwindigkeitsdispersionsfelder räumlich überlagert zu Hubble-Weltraumteleskop-Bildaufnahmen der Lyα und Hα Strahlungsströme.  Aus diesen Beobachtungen können wir schlussfolgern, dass in einigen Galaxien kausale Zusammenhänge zwischen der Hα-Kinematik und der Lyα-Photometrie bestehen.  Statistisch signifikant finden wir, dass Galaxien, bei denen chaotische Dispersionsbewegungen dominieren, wahrscheinlicher Lyα Strahlung abgeben als Galaxien bei denen die Gasbewegungen durch geordnete Bewegungen dominiert sind.  Dieses Resultat ist ein Indiz dafür, dass Turbulenz im interstellaren Medium aktiv sternbildender Galaxien schafft, welche ein Austreten der Lyα-Strahlung begünstigen.

Neben massereichen Sternen kann nicht-thermische Strahlung eines akretierenden supermassereichen schwarzen Loches eine weitere Energiequelle zur Erzeugung von Lyα Strahlung sein.  Wenn eine Galaxie einen solchen aktiven Galaxienkern enthält, kann die Rate der ionisierenden Photonen 1000-mal höher sein als bei einer normalen sternbildenden Galaxie.  Diese Strahlung hat das Potential große Bereiche weit ausserhalb der Sternansammlungen der Galaxien zu ionisieren.  Deshalb ist zu erwarten, dass der neutrale Wasserstoff in diesen zirkum-galaktischen Gebieten in Lyα-Strahlung fluoresziert.  Dieses zirkum-galaktische Gas spielt eine wesentliche Rolle bei der Entwicklung von Galaxien.  Zum Einen ist es das Reservoir aus denen Sternentstehungsprozesse ihr Gas beziehen, zum Anderen ist es Wechselwirkungsprozessen ausgesetzt, bei denen Gas aus der Galaxie hinausgeschleudert wird.  Wenn Lyα-Strahlung dieses zirkum-galaktischen Mediums detektiert werden könnte, ließen sich diese fundamentalen Prozesse der Galaxienentwicklung detaillierter studieren.  In Kapitel 3 dieser Arbeit zeigen wir PMAS Beobachtungsdaten von 5 radio-leisen Quasaren in denen wir nach dieser ausgedehnten Lyα-Strahlung gesucht haben.  Jedoch haben wir für 4 unserer Quasare keine signifikanten Spuren dieser ausgedehnten Strahlung entdecken können.  Im fünften Objekt finden wir in Entfernung von einigen Kiloparsec zum Kern Anzeichen für eine schwache und räumlich eher kompakte Quelle. Deartig schwache Flüsse von solchen Strukturen erscheinen konsistent mit der Annahme, dass radio-leise Quasare sich in Halos aus dunkler Materie mit eher moderaten Massen befinden.  Obwohl wir nicht direkt Lyα-Strahlung vom zirkum-galaktischen Medium detektieren konnten, sind unsere Detektionsgrenzen von Nutzem bei der Planung von diesbezüglichen Beobachtungen mit der neuen Generation von Integralfeldspektrographen an 8--10m Teleskopen.

Ein derartiges Instrument ist der Multi Unit Spectroscopic Explorer (MUSE) am ESO Very Large Telescope.  Einer der Hauptbeweggründe für dessen Konstruktion war die Verwendung als Durchmusterungsinstrument für Lyα emittierende Galaxien bei hohen Rotverschiebungen.  Aktuell führen wir eine derartige Durchmusterungskampagne durch.  Nach deren Abschluss, werden wir eine Fläche von 100 Quadratbogenminuten durchmustert haben.  In Kapitel 5 dieser Arbeit präsentieren wir als erstes Resultat einen Katalog von 831 Emissionslinienselektierten Galaxien in einer 22.2 Quadratbogenminuten großen Region im Chandra Deep Field South.  Um diesen Katalog zu erzeugen, haben wir eine neuartige Quellendetektionsmethode für integralfeldspektroskopische Datensätze entwickelt und implementiert (Kapitel 4).  Unser Katalog enthält 237 Lyα emittierende Galaxien bei Rotverschiebungen 3 ≲ z ≲ 6.  Aufgrund ihrer geringen Kontinuumsflussdichten existierten zuvor nur von 4 dieser Galaxien spektroskopische Rotverschiebungen.  Als Abschluss dieser Arbeit präsentieren wir einen Ausbick bezüglich der Konstruktion einer Leuchtkraftfunktion dieser einzigartigen Lyα Galaxienstichprobe (Kapitel 6).
KW  - astrophysics
KW  - galaxies
KW  - high redshift galaxies
KW  - integral field spectroscopy
KW  - quasars
KW  - Astrophysik
KW  - Galaxien
KW  - Galaxien bei hoher Rotverschiebung
KW  - Integralfeldspektroskopie
KW  - Quasare
Y1  - 2016
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-102341
ER  - 
TY  - JOUR
A1  - Hic, Ceren
A1  - Pradhan, Prajal
A1  - Rybski, Diego
A1  - Kropp, Jürgen
T1  - Food Surplus and Its Climate Burdens
JF  - Geological Society of America bulletin
N2  - Avoiding food loss and waste may counteract the increasing food demand and reduce greenhouse gas (GHG) emissions from the agricultural sector. This is crucial because of limited options available to increase food production. In the year 2010, food availability was 20% higher than was required on a global scale. Thus, a more sustainable food production and adjusted consumption would have positive environmental effects. This study provides a systematic approach to estimate consumer level food waste on a country scale and globally, based on food availability and requirements. The food requirement estimation considers demographic development, body weights, and physical activity levels. Surplus between food availability and requirements of a given country is considered as food waste. The global food requirement changed from 2,300 kcal/cap/day to 2,400 kcal/cap/day during the last 50 years, while food surplus grew from 310 kcal/cap/day to 510 kcal/cap/day. Similarly, GHG emissions related to the food surplus increased from 130 Mt CO2eq/yr to 530 Mt CO2eq/yr, an increase of more than 300%. Moreover, the global food surplus may increase up to 850 kcal/cap/day, while the total food requirement will increase only by 2%-20% by 2050. Consequently, GHG emissions associated with the food waste may also increase tremendously to 1.9-2.5 Gt CO2eq/yr.
Y1  - 2016
U6  - https://doi.org/10.1021/acs.est.5b05088
SN  - 0013-936X
SN  - 1520-5851
VL  - 50
SP  - 4269
EP  - 4277
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Holländer, Lars
A1  - Kossack, Wilhelm
A1  - Kollosche, Matthias
A1  - Wirges, Werner
A1  - Kremer, Friedrich
A1  - Gerhard, Reimund
T1  - Influence of the remanent polarisation on the liquid crystal alignment in composite films of ferroelectric poly(vinylidene fluoride-trifluoroethylene) and a cyanobiphenyl-based liquid crystal
JF  - Liquid crystals : an international journal of science and technology
N2  - Polymer-dispersed liquid crystals (PDLCs) of ferroelectric poly(vinylidene fluoride-trifluoroethylene) and nematic 4-cyano-4&#697;-n-hexylbiphenyl (6CB) or 4-cyano-4&#697;-n-pentylbiphenyl (5CB) were prepared to study the effect of the remanent polarisation of the polymer on the liquid crystal alignment. We measured the macroscopic alignment of the liquid crystal molecules in the thickness direction by means of Infrared Transition-Moment Orientational Analysis. Electrical poling at 100 V/µm caused an increased order parameter up to 0.15. After subsequent annealing above the nematic-to-isotropic phase-transition temperature, the order parameter was reduced to 0.02. Nevertheless, the order parameter was still higher than for non-poled film indicating a slight orientation in thickness direction. Both values are lower than those expected from model calculations. In agreement with dielectric measurements, we attribute this result to the shielding effect of mobile charge carriers within the liquid crystal inclusions.
KW  - Polymer-dispersed liquid crystal
KW  - ferroelectric polymer
KW  - remanent polarisation
KW  - liquid crystal alignment
Y1  - 2016
U6  - https://doi.org/10.1080/02678292.2016.1185174
SN  - 0267-8292
SN  - 1366-5855
VL  - 43
SP  - 1514
EP  - 1521
PB  - Editions Rodopi BV
CY  - Abingdon
ER  - 
TY  - JOUR
A1  - Hubrig, Swetlana
A1  - Kholtygin, A.
A1  - Ilyin, Ilya
A1  - Schöller, M.
A1  - Oskinova, Lida
T1  - THE FIRST SPECTROPOLARIMETRIC MONITORING OF THE PECULIAR O4 Ief SUPERGIANT zeta PUPPIS
JF  - The astrophysical journal : an international review of spectroscopy and astronomical physics
N2  - The origin of the magnetic field in massive O-type stars is still under debate. To model the physical processes responsible for the generation of O star magnetic fields, it is important to understand whether correlations between the presence of a magnetic field and stellar evolutionary state, rotation velocity, kinematical status, and surface composition can be identified. The O4 Ief supergiant zeta Pup is a fast rotator and a runaway star, which may be a product of a past binary interaction, possibly having had an encounter with the cluster Trumper 10 some 2 Myr ago. The currently available observational material suggests that certain observed phenomena in this star may be related to the presence of a magnetic field. We acquired spectropolarimetric observations of zeta Pup with FORS 2 mounted on the 8 m Antu telescope of the Very Large Telescope to investigate if a magnetic field is indeed present in this star. We show that many spectral lines are highly variable and probably vary with the recently detected period of 1.78 day. No magnetic field is detected in zeta Pup, as no magnetic field measurement has a significance level higher than 2.4 sigma. Still, we studied the probability of a single sinusoidal explaining the variation of the longitudinal magnetic field measurements.
KW  - stars: atmospheres
KW  - stars: early-type
KW  - stars: individual (zetaPup)
KW  - stars: magnetic field
KW  - stars: variables: general
Y1  - 2016
U6  - https://doi.org/10.3847/0004-637X/822/2/104
SN  - 0004-637X
SN  - 1538-4357
VL  - 822
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Hubrig, Swetlana
A1  - Scholz, Kathleen
A1  - Hamann, Wolf-Rainer
A1  - Schoeller, M.
A1  - Ignace, R.
A1  - Ilyin, Ilya
A1  - Gayley, K. G.
A1  - Oskinova, Lida
T1  - Searching for a magnetic field in Wolf-Rayet stars using FORS 2 spectropolarimetry
JF  - Monthly notices of the Royal Astronomical Society
N2  - To investigate if magnetic fields are present in Wolf-Rayet stars, we selected a few stars in the Galaxy and one in the Large Magellanic Cloud (LMC). We acquired low-resolution spectropolarimetric observations with the European Southern Observatory FORS 2 (FOcal Reducer low dispersion Spectrograph) instrument during two different observing runs. During the first run in visitor mode, we observed the LMC Wolf-Rayet star BAT99 7 and the stars WR 6, WR 7, WR 18, and WR 23 in our Galaxy. The second run in service mode was focused on monitoring the star WR 6. Linear polarization was recorded immediately after the observations of circular polarization. During our visitor observing run, the magnetic field for the cyclically variable star WR 6 was measured at a significance level of 3.3 sigma (< B-z > = 258 +/- 78 G). Among the other targets, the highest value for the longitudinal magnetic field, < B-z > = 327 +/- 141 G, was measured in the LMC star BAT99 7. Spectropolarimetric monitoring of the star WR 6 revealed a sinusoidal nature of the < B-z > variations with the known rotation period of 3.77 d, significantly adding to the confidence in the detection. The presence of the rotation-modulated magnetic variability is also indicated in our frequency periodogram. The reported field magnitude suffers from significant systematic uncertainties at the factor of 2 level, in addition to the quoted statistical uncertainties, owing to the theoretical approach used to characterize it. Linear polarization measurements showed no line effect in the stars, apart from WR 6. BAT99 7, WR 7, and WR 23 do not show variability of the linear polarization over two nights.
KW  - techniques: polarimetric
KW  - stars: individual: WR 6
KW  - stars: magnetic field
KW  - stars: variables: general
KW  - stars: Wolf-Rayet
Y1  - 2016
U6  - https://doi.org/10.1093/mnras/stw558
SN  - 0035-8711
SN  - 1365-2966
VL  - 458
SP  - 3381
EP  - 3393
PB  - Oxford Univ. Press
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Husser, Tim-Oliver
A1  - Kamann, Sebastian
A1  - Dreizler, Stefan
A1  - Wendt, Martin
A1  - Wulff, Nina
A1  - Bacon, Roland
A1  - Wisotzki, Lutz
A1  - Brinchmann, Jarle
A1  - Weilbacher, Peter Michael
A1  - Roth, Martin M.
A1  - Monreal-Ibero, Ana
T1  - MUSE crowded field 3D spectroscopy of over 12 000 stars in the globular cluster NGC 6397 I. The first comprehensive HRD of a globular cluster
JF  - Nucleic acids research
N2  - Aims. We demonstrate the high multiplex advantage of crowded field 3D spectroscopy with the new integral field spectrograph MUSE by means of a spectroscopic analysis of more than 12 000 individual stars in the globular cluster NGC 6397. Methods. The stars are deblended with a point spread function fitting technique, using a photometric reference catalogue from HST as prior, including relative positions and brightnesses. This catalogue is also used for a first analysis of the extracted spectra, followed by an automatic in-depth analysis via a full-spectrum fitting method based on a large grid of PHOENIX spectra. Results. We analysed the largest sample so far available for a single globular cluster of 18 932 spectra from 12 307 stars in NGC 6397. We derived a mean radial velocity of v(rad) = 17.84 +/- 0.07 km s(-1) and a mean metallicity of [Fe/H] = -2.120 +/- 0.002, with the latter seemingly varying with temperature for stars on the red giant branch (RGB). We determine Teff and [Fe/H] from the spectra, and log g from HST photometry. This is the first very comprehensive Hertzsprung-Russell diagram (HRD) for a globular cluster based on the analysis of several thousands of stellar spectra, ranging from the main sequence to the tip of the RGB. Furthermore, two interesting objects were identified; one is a post-AGB star and the other is a possible millisecond-pulsar companion.
KW  - methods: data analysis
KW  - techniques: imaging spectroscopy
KW  - planets and satellites: fundamental parameters
KW  - stars: atmospheres
KW  - pulsars: general
KW  - globular clusters: individual: NGC 6397
Y1  - 2016
U6  - https://doi.org/10.1051/0004-6361/201526949
SN  - 1432-0746
VL  - 588
PB  - EDP Sciences
CY  - Les Ulis
ER  - 
TY  - JOUR
A1  - Intravaia, F.
A1  - Behunin, R. O.
A1  - Henkel, Carsten
A1  - Busch, K.
A1  - Dalvit, D. A. R.
T1  - Failure of Local Thermal Equilibrium in Quantum Friction
JF  - Physical review letters
N2  - Recent progress in manipulating atomic and condensed matter systems has instigated a surge of interest in nonequilibrium physics, including many-body dynamics of trapped ultracold atoms and ions, near-field radiative heat transfer, and quantum friction. Under most circumstances the complexity of such nonequilibrium systems requires a number of approximations to make theoretical descriptions tractable. In particular, it is often assumed that spatially separated components of a system thermalize with their immediate surroundings, although the global state of the system is out of equilibrium. This powerful assumption reduces the complexity of nonequilibrium systems to the local application of well-founded equilibrium concepts. While this technique appears to be consistent for the description of some phenomena, we show that it fails for quantum friction by underestimating by approximately 80% the magnitude of the drag force. Our results show that the correlations among the components of driven, but steady-state, quantum systems invalidate the assumption of local thermal equilibrium, calling for a critical reexamination of this approach for describing the physics of nonequilibrium systems.
Y1  - 2016
U6  - https://doi.org/10.1103/PhysRevLett.117.100402
SN  - 0031-9007
SN  - 1079-7114
VL  - 117
SP  - 989
EP  - 1010
PB  - American Physical Society
CY  - College Park
ER  - 
TY  - JOUR
A1  - Intravaia, F.
A1  - Behunin, R. O.
A1  - Henkel, Carsten
A1  - Busch, K.
A1  - Dalvit, D. A. R.
T1  - Non-Markovianity in atom-surface dispersion forces
JF  - Physical review : A, Atomic, molecular, and optical physics
N2  - We discuss the failure of the Markov approximation in the description of atom-surface fluctuation-induced interactions, both in equilibrium (Casimir-Polder forces) and out of equilibrium (quantum friction). Using general theoretical arguments, we show that the Markov approximation can lead to erroneous predictions of such phenomena with regard to both strength and functional dependencies on system parameters. In particular, we show that the long-time power-law tails of two-time dipole correlations and their corresponding low-frequency behavior, neglected in the Markovian limit, affect the prediction of the force. Our findings highlight the importance of non-Markovian effects in dispersion interactions.
Y1  - 2016
U6  - https://doi.org/10.1103/PhysRevA.94.042114
SN  - 2469-9926
SN  - 2469-9934
VL  - 94
PB  - American Physical Society
CY  - College Park
ER  - 
TY  - JOUR
A1  - Iurchuk, V.
A1  - Schick, D.
A1  - Bran, J.
A1  - Colson, D.
A1  - Forget, A.
A1  - Halley, D.
A1  - Koc, Azize
A1  - Reinhardt, Mathias
A1  - Kwamen, C.
A1  - Morley, N. A.
A1  - Bargheer, Matias
A1  - Viret, M.
A1  - Gumeniuk, R.
A1  - Schmerber, G.
A1  - Doudin, B.
A1  - Kundys, B.
T1  - Optical Writing of Magnetic Properties by Remanent Photostriction
JF  - Physical review letters
N2  - We present an optically induced remanent photostriction in BiFeO3, resulting from the photovoltaic effect, which is used to modify the ferromagnetism of Ni film in a hybrid BiFeO3/Ni structure. The 75% change in coercivity in the Ni film is achieved via optical and nonvolatile control. This photoferromagnetic effect can be reversed by static or ac electric depolarization of BiFeO3. Hence, the strain dependent changes in magnetic properties are written optically, and erased electrically. Light-mediated straintronics is therefore a possible approach for low-power multistate control of magnetic elements relevant for memory and spintronic applications.
Y1  - 2016
U6  - https://doi.org/10.1103/PhysRevLett.117.107403
SN  - 0031-9007
SN  - 1079-7114
VL  - 117
PB  - American Physical Society
CY  - College Park
ER  - 
TY  - JOUR
A1  - Ivanov, Valentin D.
A1  - Cioni, Maria-Rosa L.
A1  - Bekki, Kenji
A1  - de Grijs, Richard
A1  - Emerson, Jim
A1  - Gibson, Brad K.
A1  - Kamath, Devika
A1  - van Loon, Jacco Th.
A1  - Piatti, Andres E.
A1  - For, Bi-Qing
T1  - New quasars behind the Magellanic Clouds. Spectroscopic confirmation of near-infrared selected candidates
JF  - Current biology
N2  - Context. Quasi-stellar objects (quasars) located behind nearby galaxies provide an excellent absolute reference system for astrometric studies, but they are difficult to identify because of fore-and background contamination. Deep wide-field, high angular resolution surveys spanning the entire area of nearby galaxies are needed to obtain a complete census of such quasars. Aims. We embarked on a program to expand the quasar reference system behind the Large and the Small Magellanic Clouds, the Magellanic Bridge, and the Magellanic Stream that connects the Clouds with the Milky Way. Methods. Hundreds of quasar candidates were selected based on their near-infrared colors and variability properties from the ongoing public ESO VISTA Magellanic Clouds survey. A subset of 49 objects was followed up with optical spectroscopy. Results. We confirmed the quasar nature of 37 objects (34 new identifications): four are low redshift objects, three are probably stars, and the remaining three lack prominent spectral features for a secure classification. The bona fide quasars, identified from their broad emisison lines, are located as follows: 10 behind the LMC, 13 behind the SMC, and 14 behind the Bridge. The quasars span a redshift range from z similar to 0.5 to z similar to 4.1. Conclusions. Upon completion the VMC survey is expected to yield a total of similar to 1500 quasars with Y < 19.32 mag, J < 19.09 mag, and K-s < 18.04 mag.
KW  - surveys
KW  - infrared: galaxies
KW  - quasars: general
KW  - Magellanic Clouds
Y1  - 2016
U6  - https://doi.org/10.1051/0004-6361/201527398
SN  - 1432-0746
VL  - 588
PB  - EDP Sciences
CY  - Les Ulis
ER  - 
TY  - JOUR
A1  - Japha, Yonathan
A1  - Zhou, Shuyu
A1  - Keil, Mark
A1  - Folman, Ron
A1  - Henkel, Carsten
A1  - Vardi, Amichay
T1  - Suppression and enhancement of decoherence in an atomic Josephson junction
JF  - NEW JOURNAL OF PHYSICS
N2  - We investigate the role of interatomic interactions when a Bose gas, in a double-well potential with a finite tunneling probability (a 'Bose–Josephson junction'), is exposed to external noise. We examine the rate of decoherence of a system initially in its ground state with equal probability amplitudes in both sites. The noise may induce two kinds of effects: firstly, random shifts in the relative phase or number difference between the two wells and secondly, loss of atoms from the trap. The effects of induced phase fluctuations are mitigated by atom–atom interactions and tunneling, such that the dephasing rate may be suppressed by half its single-atom value. Random fluctuations may also be induced in the population difference between the wells, in which case atom–atom interactions considerably enhance the decoherence rate. A similar scenario is predicted for the case of atom loss, even if the loss rates from the two sites are equal. We find that if the initial state is number-squeezed due to interactions, then the loss process induces population fluctuations that reduce the coherence across the junction. We examine the parameters relevant for these effects in a typical atom chip device, using a simple model of the trapping potential, experimental data, and the theory of magnetic field fluctuations near metallic conductors. These results provide a framework for mapping the dynamical range of barriers engineered for specific applications and set the stage for more complex atom circuits ('atomtronics').
KW  - atomtronics
KW  - coherence
KW  - ultracold atoms
KW  - Bose-Einstein condensate
KW  - Bose-Hubbard model
KW  - tunneling
KW  - Josephson junction
Y1  - 2016
U6  - https://doi.org/10.1088/1367-2630/18/5/055008
SN  - 1367-2630
VL  - 18
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Jeon, Jae-Hyung
A1  - Javanainen, Matti
A1  - Martinez-Seara, Hector
A1  - Metzler, Ralf
A1  - Vattulainen, Ilpo
T1  - Protein Crowding in Lipid Bilayers Gives Rise to Non-Gaussian Anomalous Lateral Diffusion of Phospholipids and Proteins
JF  - Physical review : X, Expanding access
N2  - Biomembranes are exceptionally crowded with proteins with typical protein-to-lipid ratios being around 1:50 - 1:100. Protein crowding has a decisive role in lateral membrane dynamics as shown by recent experimental and computational studies that have reported anomalous lateral diffusion of phospholipids and membrane proteins in crowded lipid membranes. Based on extensive simulations and stochastic modeling of the simulated trajectories, we here investigate in detail how increasing crowding by membrane proteins reshapes the stochastic characteristics of the anomalous lateral diffusion in lipid membranes. We observe that correlated Gaussian processes of the fractional Langevin equation type, identified as the stochastic mechanism behind lipid motion in noncrowded bilayer, no longer adequately describe the lipid and protein motion in crowded but otherwise identical membranes. It turns out that protein crowding gives rise to a multifractal, non-Gaussian, and spatiotemporally heterogeneous anomalous lateral diffusion on time scales from nanoseconds to, at least, tens of microseconds. Our investigation strongly suggests that the macromolecular complexity and spatiotemporal membrane heterogeneity in cellular membranes play critical roles in determining the stochastic nature of the lateral diffusion and, consequently, the associated dynamic phenomena within membranes. Clarifying the exact stochastic mechanism for various kinds of biological membranes is an important step towards a quantitative understanding of numerous intramembrane dynamic phenomena.
Y1  - 2016
U6  - https://doi.org/10.1103/PhysRevX.6.021006
SN  - 2160-3308
VL  - 6
PB  - American Physical Society
CY  - College Park
ER  - 
TY  - JOUR
A1  - Kamann, S.
A1  - Husser, T. -O.
A1  - Brinchmann, Jarle
A1  - Emsellem, E.
A1  - Weilbacher, Peter Michael
A1  - Wisotzki, Lutz
A1  - Wendt, Martin
A1  - Krajnovic, D.
A1  - Roth, M. M.
A1  - Bacon, Roland
A1  - Dreizler, S.
T1  - MUSE crowded field 3D spectroscopy of over 12 000 stars in the globular cluster NGC 6397
JF  - Tectonophysics : international journal of geotectonics and the geology and physics of the interior of the earth
N2  - We present a detailed analysis of the kinematics of the Galactic globular cluster NGC 6397 based on more than similar to 18 000 spectra obtained with the novel integral field spectrograph MUSE. While NGC 6397 is often considered a core collapse cluster, our analysis suggests a flattening of the surface brightness profile at the smallest radii. Although it is among the nearest globular clusters, the low velocity dispersion of NGC 6397 of < 5 km s(-1) imposes heavy demands on the quality of the kinematical data. We show that despite its limited spectral resolution, MUSE reaches an accuracy of 1 km s(-1) in the analysis of stellar spectra. We find slight evidence for a rotational component in the cluster and the velocity dispersion profile that we obtain shows a mild central cusp. To investigate the nature of this feature, we calculate spherical Jeans models and compare these models to our kinematical data. This comparison shows that if a constant mass-to-light ratio is assumed, the addition of an intermediate-mass black hole with a mass of 600 M-circle dot brings the model predictions into agreement with our data, and therefore could be at the origin of the velocity dispersion profile. We further investigate cases with varying mass-to-light ratios and find that a compact dark stellar component can also explain our observations. However, such a component would closely resemble the black hole from the constant mass-to-light ratio models as this component must be confined to the central similar to 5 ' of the cluster and must have a similar mass. Independent constraints on the distribution of stellar remnants in the cluster or kinematic measurements at the highest possible spatial resolution should be able to distinguish the two alternatives.
KW  - globular clusters: individual: NGC 6397
KW  - stars: kinematics and dynamics
KW  - techniques: radial velocities
KW  - techniques: imaging spectroscopy
KW  - black hole physics
Y1  - 2016
U6  - https://doi.org/10.1051/0004-6361/201527065
SN  - 1432-0746
VL  - 588
PB  - EDP Sciences
CY  - Les Ulis
ER  - 
TY  - JOUR
A1  - Kappel, David
A1  - Arnold, Gabriele
A1  - Haus, Rainer
T1  - Multi-spectrum retrieval of Venus IR surface emissivity maps from VIRTIS/VEX nightside measurements at Themis Regio
JF  - Icarus : international journal of solar system studies
N2  - Renormalized emissivity maps of Themis Regio at the three surface windows are determined from 64 measurement repetitions. Retrieval errors are estimated by a statistical evaluation of maps derived from various disjoint selections of spectra and using different assumptions on the interfering parameters. Double standard deviation errors for the three surface windows amount to 3%, 8%, and 4%, respectively, allowing geologic interpretation. A comparison to results from an earlier error analysis based on synthetic spectra shows that unconsidered time variations of interfering atmospheric parameters are a major error source. Spatial variations of the 1.02 mu m surface emissivity of 20% that correspond to the difference between unweathered granitic and basaltic rocks would be easily detectable, but such variations are ruled out for the studied target area. Emissivity anomalies of up to 8% are detected at both 1.02 and 1.18 mu m. At present sensitivity, no anomalies are identified at 1.10 mu m, but anomalies exceeding the determined error level can be excluded. With single standard deviation significance, all three maps show interesting spatial emissivity variations. (C) 2015 Elsevier Inc. All rights reserved.
KW  - Venus, surface
KW  - Infrared observations
KW  - Radiative transfer
Y1  - 2016
U6  - https://doi.org/10.1016/j.icarus.2015.10.014
SN  - 0019-1035
SN  - 1090-2643
VL  - 265
SP  - 42
EP  - 62
PB  - Elsevier
CY  - San Diego
ER  - 
TY  - JOUR
A1  - Kegeles, Alexander
A1  - Oriti, Daniele
T1  - Generalized conservation laws in non-local field theories
JF  - Journal of physics : A, Mathematical and theoretical
N2  - We propose a geometrical treatment of symmetries in non-local field theories, where the non-locality is due to a lack of identification of field arguments in the action. We show that the existence of a symmetry of the action leads to a generalized conservation law, in which the usual conserved current acquires an additional non-local correction term, obtaining a generalization of the standard Noether theorem. We illustrate the general formalism by discussing the specific physical example of complex scalar field theory of the type describing the hydrodynamic approximation of Bose-Einstein condensates. We expect our analysis and results to be of particular interest for the group field theory formulation of quantum gravity.
KW  - conservation laws
KW  - non-local field theory
KW  - Noether theorem
KW  - group field theory
Y1  - 2016
U6  - https://doi.org/10.1088/1751-8113/49/13/135401
SN  - 1751-8113
SN  - 1751-8121
VL  - 49
SP  - 119
EP  - 134
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Kim, Kyung-Chan
A1  - Shprits, Yuri Y.
A1  - Blake, J. Bernard
T1  - Fast injection of the relativistic electrons into the inner zone and the formation of the split-zone structure during the Bastille Day storm in July 2000
JF  - Journal of geophysical research : Space physics
N2  - During the July 2000 geomagnetic storm, known as the Bastille Day storm, Solar, Anomalous, and Magnetospheric Particle Explorer (SAMPEX)/Heavy Ion Large Telescope (HILT) observed a strong injection of similar to 1MeV electrons into the slot region (L similar to 2.5) during the storm main phase. Then, during the following month, electrons were clearly seen diffusing inward down to L=2 and forming a pronounced split structure encompassing a narrow, newly formed slot region around L=3. SAMPEX observations are first compared with electron and proton observations on HEO-3 and NOAA-15 to validate that the observed unusual dynamics was not caused by proton contamination of the SAMPEX instrument. The time-dependent 3-D Versatile Electron Radiation Belt (VERB) simulation of 1MeV electron flux evolution is compared with the SAMPEX/HILT observations. The results show that the VERB code predicts overall time evolution of the observed split structure. The simulated split structure is produced by pitch angle scattering into the Earth atmosphere of similar to 1MeV electrons by plasmaspheric hiss.
KW  - inner radiation zone and slot region
KW  - Bastille Day geomagnetic storm
KW  - 3-D diffusion simulation
KW  - plasmaspheric hiss
Y1  - 2016
U6  - https://doi.org/10.1002/2015JA022072
SN  - 2169-9380
SN  - 2169-9402
VL  - 121
SP  - 8329
EP  - 8342
PB  - American Geophysical Union
CY  - Washington
ER  -