@article{WilhelmTelezhinskyDwarkadasetal.2020, author = {Wilhelm, Alina and Telezhinsky, Igor and Dwarkadas, Vikram V. and Pohl, Martin}, title = {Stochastic re-acceleration and magnetic-field damping in Tycho's supernova remnant}, series = {Astronomy and astrophysics}, volume = {639}, journal = {Astronomy and astrophysics}, publisher = {EDP Sciences}, address = {Les Ulis}, issn = {0004-6361}, doi = {10.1051/0004-6361/201936079}, pages = {14}, year = {2020}, abstract = {Context. Tycho's supernova remnant (SNR) is associated with the historical supernova (SN) event SN 1572 of Type Ia. The explosion occurred in a relatively clean environment, and was visually observed, providing an age estimate. This SNR therefore represents an ideal astrophysical test-bed for the study of cosmic-ray acceleration and related phenomena. A number of studies suggest that shock acceleration with particle feedback and very efficient magnetic-field amplification combined with Alfvenic drift are needed to explain the rather soft radio spectrum and the narrow rims observed in X-rays. Aims. We show that the broadband spectrum of Tycho's SNR can alternatively be well explained when accounting for stochastic acceleration as a secondary process. The re-acceleration of particles in the turbulent region immediately downstream of the shock should be efficient enough to impact particle spectra over several decades in energy. The so-called Alfvenic drift and particle feedback on the shock structure are not required in this scenario. Additionally, we investigate whether synchrotron losses or magnetic-field damping play a more profound role in the formation of the non-thermal filaments. Methods. We solved the full particle transport equation in test-particle mode using hydrodynamic simulations of the SNR plasma flow. The background magnetic field was either computed from the induction equation or follows analytic profiles, depending on the model considered. Fast-mode waves in the downstream region provide the diffusion of particles in momentum space. Results. We show that the broadband spectrum of Tycho can be well explained if magnetic-field damping and stochastic re-acceleration of particles are taken into account. Although not as efficient as standard diffusive shock acceleration, stochastic acceleration leaves its imprint on the particle spectra, which is especially notable in the emission at radio wavelengths. We find a lower limit for the post-shock magnetic-field strength similar to 330 mu G, implying efficient amplification even for the magnetic-field damping scenario. Magnetic-field damping is necessary for the formation of the filaments in the radio range, while the X-ray filaments are shaped by both the synchrotron losses and magnetic-field damping.}, language = {en} } @article{BohdanNiemiecPohletal.2019, author = {Bohdan, Artem and Niemiec, Jacek and Pohl, Martin and Matsumoto, Yosuke and Amano, Takanobu and Hoshino, Masahiro}, title = {Kinetic Simulations of Nonrelativistic Perpendicular Shocks of Young Supernova Remnants}, series = {The astrophysical journal : an international review of spectroscopy and astronomical physics}, volume = {878}, journal = {The astrophysical journal : an international review of spectroscopy and astronomical physics}, number = {1}, publisher = {IOP Publ. Ltd.}, address = {Bristol}, issn = {0004-637X}, doi = {10.3847/1538-4357/ab1b6d}, pages = {11}, year = {2019}, abstract = {Electron injection at high Mach number nonrelativistic perpendicular shocks is studied here for parameters that are applicable to young SNR shocks. Using high-resolution large-scale two-dimensional fully kinetic particle-in-cell simulations and tracing individual particles, we in detail analyze the shock-surfing acceleration (SSA) of electrons at the leading edge of the shock foot. The central question is to what degree the process can be captured in 2D3V simulations. We find that the energy gain in SSA always arises from the electrostatic field of a Buneman wave. Electron energization is more efficient in the out-of-plane orientation of the large-scale magnetic field because both the phase speed and the amplitude of the waves are higher than for the in-plane scenario. Also, a larger number of electrons is trapped by the waves compared to the in-plane configuration. We conclude that significant modifications of the simulation parameters are needed to reach the same level of SSA efficiency as in simulations with out-of-plane magnetic field or 3D simulations.}, language = {en} } @article{AbdallaAharonianBenkhalietal.2019, author = {Abdalla, Hassan E. and Aharonian, Felix A. and Benkhali, F. Ait and Ang{\"u}ner, Ekrem Oǧuzhan and Arakawa, M. and Arcaro, C. and Armand, C. and Backes, M. and Barnard, M. and Becherini, Y. and Berge, D. and Bernloehr, K. and Blackwell, R. and Bottcher, M. and Boisson, C. and Bolmont, J. and Bonnefoy, S. and Bregeon, J. and Brun, F. and Brun, P. and Bryan, M. and Buechele, M. and Bulik, T. and Bylund, T. and Capasso, M. and Caroff, S. and Carosi, A. and Casanova, Sabrina and Cerruti, M. and Chakraborty, N. and Chand, T. and Chandra, S. and Chaves, R. C. G. and Chen, A. and Colafrancesco, S. and Condon, B. and Davids, I. D. and Deil, C. and Devin, J. and deWilt, P. and Dirson, L. and Djannati-Atai, A. and Dmytriiev, A. and Donath, A. and Doroshenko, V and Dyks, J. and Egberts, Kathrin and Emery, G. and Ernenwein, J-P and Eschbach, S. and Feijen, K. and Fegan, S. and Fiasson, A. and Fontaine, G. and Funk, S. and Fuessling, M. and Gabici, S. and Gallant, Y. A. and Gate, F. and Giavitto, G. and Glawion, D. and Glicenstein, J. F. and Gottschall, D. and Grondin, M-H and Hahn, J. and Haupt, M. and Heinzelmann, G. and Henri, G. and Hermann, G. and Hinton, James Anthony and Hofmann, W. and Hoischen, Clemens and Holch, Tim Lukas and Holler, M. and Horns, D. and Huber, D. and Iwasaki, H. and Jacholkowska, A. and Jamrozy, M. and Jankowsky, D. and Jankowsky, F. and Jouvin, L. and Jung-Richardt, I and Kastendieck, M. A. and Katarzynski, K. and Katsuragawa, M. and Katz, U. and Khangulyan, D. and Khelifi, B. and King, J. and Klepser, S. and Kluzniak, W. and Komin, Nu and Kosack, K. and Kostunin, D. and Kraus, M. and Lamanna, G. and Lau, J. and Lemiere, A. and Lemoine-Goumard, M. and Lenain, J-P and Leser, Eva and Lohse, T. and Lopez-Coto, R. and Lypova, I and Malyshev, D. and Marandon, V and Marcowith, Alexandre and Mariaud, C. and Marti-Devesa, G. and Marx, R. and Maurin, G. and Maxted, N. and Meintjes, P. J. and Mitchell, A. M. W. and Moderski, R. and Mohamed, M. and Mohrmann, L. and Moore, C. and Moulin, Emmanuel and Murach, T. and Nakashima, S. and de Naurois, M. and Ndiyavala, H. and Niederwanger, F. and Niemiec, J. and Oakes, L. and Odaka, H. and Ohm, S. and Wilhelmi, E. de Ona and Ostrowski, M. and Oya, I and Panter, M. and Parsons, R. D. and Perennes, C. and Petrucci, P-O and Peyaud, B. and Piel, Q. and Pita, S. and Poireau, V and Noel, A. Priyana and Prokhorov, D. A. and Prokoph, H. and Puehlhofer, G. and Punch, M. and Quirrenbach, A. and Raab, S. and Rauth, R. and Reimer, A. and Reimer, O. and Renaud, M. and Rieger, F. and Rinchiuso, L. and Romoli, C. and Rowell, G. and Rudak, B. and Ruiz-Velasco, E. and Sahakian, V and Saito, S. and Sanchez, David M. and Santangelo, A. and Sasaki, M. and Schlickeiser, R. and Schussler, F. and Schulz, A. and Schutte, H. and Schwanke, U. and Schwemmer, S. and Seglar-Arroyo, M. and Senniappan, M. and Seyffert, A. S. and Shafi, N. and Shilon, I and Shiningayamwe, K. and Simoni, R. and Sinha, A. and Sol, H. and Specovius, A. and Spir-Jacob, M. and Stawarz, L. and Steenkamp, R. and Stegmann, Christian and Steppa, Constantin Beverly and Takahashi, T. and Tavernet, J-P and Tavernier, T. and Taylor, A. M. and Terrier, R. and Tibaldo, Luigi and Tiziani, D. and Tluczykont, M. and Trichard, C. and Tsirou, M. and Tsuji, N. and Tuffs, R. and Uchiyama, Y. and van der Walt, D. J. and van Eldik, C. and van Rensburg, C. and van Soelen, B. and Vasileiadis, G. and Veh, J. and Venter, C. and Vincent, P. and Vink, J. and Voisin, F. and Voelk, H. J. and Vuillaume, T. and Wadiasingh, Z. and Wagner, S. J. and White, R. and Wierzcholska, A. and Yang, R. and Yoneda, H. and Zaborov, D. and Zacharias, M. and Zanin, R. and Zdziarski, A. A. and Zech, Alraune and Ziegler, A. and Zorn, J. and Zywucka, N.}, title = {H.E.S.S. and Suzaku observations of the Vela X pulsar wind nebula}, series = {Astronomy and astrophysics : an international weekly journal}, volume = {627}, journal = {Astronomy and astrophysics : an international weekly journal}, publisher = {EDP Sciences}, address = {Les Ulis}, organization = {HESS Collaboration}, issn = {1432-0746}, doi = {10.1051/0004-6361/201935458}, pages = {16}, year = {2019}, abstract = {Context. Pulsar wind nebulae (PWNe) represent the most prominent population of Galactic very-high-energy gamma-ray sources and are thought to be an efficient source of leptonic cosmic rays. Vela X is a nearby middle-aged PWN, which shows bright X-ray and TeV gamma-ray emission towards an elongated structure called the cocoon. Aims. Since TeV emission is likely inverse-Compton emission of electrons, predominantly from interactions with the cosmic microwave background, while X-ray emission is synchrotron radiation of the same electrons, we aim to derive the properties of the relativistic particles and of magnetic fields with minimal modelling. Methods. We used data from the Suzaku XIS to derive the spectra from three compact regions in Vela X covering distances from 0.3 to 4 pc from the pulsar along the cocoon. We obtained gamma-ray spectra of the same regions from H.E.S.S. observations and fitted a radiative model to the multi-wavelength spectra. Results. The TeV electron spectra and magnetic field strengths are consistent within the uncertainties for the three regions, with energy densities of the order 10(-12) erg cm(-3). The data indicate the presence of a cutoff in the electron spectrum at energies of similar to 100 TeV and a magnetic field strength of similar to 6 mu G. Constraints on the presence of turbulent magnetic fields are weak. Conclusions. The pressure of TeV electrons and magnetic fields in the cocoon is dynamically negligible, requiring the presence of another dominant pressure component to balance the pulsar wind at the termination shock. Sub-TeV electrons cannot completely account for the missing pressure, which may be provided either by relativistic ions or from mixing of the ejecta with the pulsar wind. The electron spectra are consistent with expectations from transport scenarios dominated either by advection via the reverse shock or by diffusion, but for the latter the role of radiative losses near the termination shock needs to be further investigated in the light of the measured cutoff energies. Constraints on turbulent magnetic fields and the shape of the electron cutoff can be improved by spectral measurements in the energy range greater than or similar to 10 keV.}, language = {en} } @article{BroseSushchPohletal.2019, author = {Brose, Robert and Sushch, Iuri and Pohl, Martin and Luken, K. J. and Filipovic, M. D. and Lin, R.}, title = {Nonthermal emission from the reverse shock of the youngest galactic supernova remnant G1.9+0.3}, series = {Astronomy and astrophysics : an international weekly journal}, volume = {627}, journal = {Astronomy and astrophysics : an international weekly journal}, publisher = {EDP Sciences}, address = {Les Ulis}, issn = {1432-0746}, doi = {10.1051/0004-6361/201834430}, pages = {9}, year = {2019}, abstract = {Context. The youngest Galactic supernova remnant G1.9+0.3 is an interesting target for next-generation gamma-ray observatories. So far, the remnant is only detected in the radio and the X-ray bands, but its young age of approximate to 100 yr and inferred shock speed of approximate to 14 000 km s(-1) could make it an efficient particle accelerator. Aims. We aim to model the observed radio and X-ray spectra together with the morphology of the remnant. At the same time, we aim to estimate the gamma-ray flux from the source and evaluate the prospects of its detection with future gamma-ray experiments. Methods. We performed spherical symmetric 1D simulations with the RATPaC code, in which we simultaneously solved the transport equation for cosmic rays, the transport equation for magnetic turbulence, and the hydro-dynamical equations for the gas flow. Separately computed distributions of the particles accelerated at the forward and the reverse shock were then used to calculate the spectra of synchrotron, inverse Compton, and pion-decay radiation from the source. Results. The emission from G1.9+0.3 can be self-consistently explained within the test-particle limit. We find that the X-ray flux is dominated by emission from the forward shock while most of the radio emission originates near the reverse shock, which makes G1.9+0.3 the first remnant with nonthermal radiation detected from the reverse shock. The flux of very-high-energy gamma-ray emission from G1.9+0.3 is expected to be close to the sensitivity threshold of the Cherenkov Telescope Array. The limited time available to grow large-scale turbulence limits the maximum energy of particles to values below 100 TeV, hence G1.9+0.3 is not a PeVatron.}, language = {en} } @article{AbdallaAharonianBenkhalietal.2019, author = {Abdalla, Hassan E. and Aharonian, Felix A. and Benkhali, F. Ait and Ang{\"u}ner, Ekrem Oǧuzhan and Arakawa, M. and Arcaro, C. and Armand, C. and Arrieta, M. and Backes, M. and Barnard, M. and Becherini, Y. and Tjus, J. Becker and Berge, D. and Bernloehr, K. and Blackwell, R. and Bottcher, M. and Boisson, C. and Bolmont, J. and Bonnefoy, S. and Bordas, Pol and Bregeon, J. and Brun, F. and Brun, P. and Bryan, M. and Buechele, M. and Bulik, T. and Bylund, T. and Capasso, M. and Caroff, S. and Carosi, A. and Casanova, Sabrina and Cerruti, M. and Chakraborty, N. and Chand, T. and Chandra, S. and Chaves, R. C. G. and Chen, A. and Colafrancesco, S. and Condon, B. and Davids, I. D. and Deil, C. and Devin, J. and deWilt, P. and Dirson, L. and Djannati-Atai, A. and Dmytriiev, A. and Donath, A. and Doroshenko, V and Dyks, J. and Egberts, Kathrin and Emery, G. and Ernenwein, J-P and Eschbach, S. and Fegan, S. and Fiasson, A. and Fontaine, G. and Funk, S. and Fuessling, M. and Gabici, S. and Gallant, Y. A. and Gate, F. and Giavitto, G. and Glawion, D. and Glicenstein, J. F. and Gottschall, D. and Grondin, M-H and Hahn, J. and Haupt, M. and Heinzelmann, G. and Henri, G. and Hermann, G. and Hinton, James Anthony and Hofmann, W. and Hoischen, Clemens and Holch, Tim Lukas and Holler, M. and Horns, D. and Huber, D. and Iwasaki, H. and Jacholkowska, A. and Jamrozy, M. and Jankowsky, D. and Jankowsky, F. and Jouvin, L. and Jung-Richardt, I and Kastendieck, M. A. and Katarzynski, K. and Katsuragawa, M. and Katz, U. and Kerszberg, D. and Khangulyan, D. and Khelifi, B. and King, J. and Klepser, S. and Kluzniak, W. and Komin, Nu and Kosack, K. and Kraus, M. and Lamanna, G. and Lau, J. and Lefaucheur, J. and Lemiere, A. and Lemoine-Goumard, M. and Lenain, J-P and Leser, Eva and Lohse, T. and Lopez-Coto, R. and Lypova, I and Malyshev, D. and Marandon, V and Marcowith, Alexandre and Mariaud, C. and Marti-Devesa, G. and Marx, R. and Maurin, G. and Meintjes, P. J. and Mitchell, A. M. W. and Moderski, R. and Mohamed, M. and Mohrmann, L. and Moore, C. and Moulin, Emmanuel and Murach, T. and Nakashima, S. and de Naurois, M. and Ndiyavala, H. and Niederwanger, F. and Niemiec, J. and Oakes, L. and Odaka, H. and Ohm, S. and Ostrowski, M. and Oya, I and Panter, M. and Parsons, R. D. and Perennes, C. and Petrucci, P-O and Peyaud, B. and Piel, Q. and Pita, S. and Poireau, V and Noel, A. Priyana and Prokhorov, D. A. and Prokoph, H. and Puehlhofer, G. and Punch, M. and Quirrenbach, A. and Raab, S. and Rauth, R. and Reimer, A. and Reimer, O. and Renaud, M. and Rieger, F. and Rinchiuso, L. and Romoli, C. and Rowell, G. and Rudak, B. and Ruiz-Velasco, E. and Sahakian, V and Saito, S. and Sanchez, David M. and Santangelo, A. and Sasaki, M. and Schlickeiser, R. and Schussler, F. and Schulz, A. and Schutte, H. and Schwanke, U. and Schwemmer, S. and Seglar-Arroyo, M. and Senniappan, M. and Seyffert, A. S. and Shafi, N. and Shilon, I and Shiningayamwe, K. and Simoni, R. and Sinha, A. and Sol, H. and Specovius, A. and Spir-Jacob, M. and Stawarz, L. and Steenkamp, R. and Stegmann, Christian and Steppa, Constantin Beverly and Takahashi, T. and Tavernet, J-P and Tavernier, T. and Taylor, A. M. and Terrier, R. and Tibaldo, L. and Tiziani, D. and Tluczykont, M. and Trichard, C. and Tsirou, M. and Tsuji, N. and Tuffs, R. and Uchiyama, Y. and van der Walt, D. J. and van Eldik, C. and van Rensburg, C. and van Soelen, B. and Vasileiadis, G. and Veh, J. and Venter, C. and Vincent, P. and Vink, J. and Voisin, F. and Voelk, H. J. and Vuillaume, T. and Wadiasingh, Z. and Wagner, S. J. and Wagner, R. M. and White, R. and Wierzcholska, A. and Yang, R. and Yoneda, H. and Zaborov, D. and Zacharias, M. and Zanin, R. and Zdziarski, A. A. and Zech, Alraune and Zefi, F. and Ziegler, A. and Zorn, J. and Zywucka, N.}, title = {Particle transport within the pulsar wind nebula HESS J1825-137}, series = {Astronomy and astrophysics : an international weekly journal}, volume = {621}, journal = {Astronomy and astrophysics : an international weekly journal}, publisher = {EDP Sciences}, address = {Les Ulis}, organization = {HESS Collaboration}, issn = {1432-0746}, doi = {10.1051/0004-6361/201834335}, pages = {18}, year = {2019}, abstract = {Context. We present a detailed view of the pulsar wind nebula (PWN) HESS J1825-137. We aim to constrain the mechanisms dominating the particle transport within the nebula, accounting for its anomalously large size and spectral characteristics. Aims. The nebula was studied using a deep exposure from over 12 years of H.E.S.S. I operation, together with data from H.E.S.S. II that improve the low-energy sensitivity. Enhanced energy-dependent morphological and spatially resolved spectral analyses probe the very high energy (VHE, E > 0.1 TeV) gamma-ray properties of the nebula. Methods. The nebula emission is revealed to extend out to 1.5 degrees from the pulsar, similar to 1.5 times farther than previously seen, making HESS J1825-137, with an intrinsic diameter of similar to 100 pc, potentially the largest gamma-ray PWN currently known. Characterising the strongly energy-dependent morphology of the nebula enables us to constrain the particle transport mechanisms. A dependence of the nebula extent with energy of R proportional to E alpha with alpha = -0.29 +/- 0.04(stat) +/- 0.05(sys) disfavours a pure diffusion scenario for particle transport within the nebula. The total gamma-ray flux of the nebula above 1 TeV is found to be (1.12 +/- 0.03(stat) +/- 0.25(sys)) +/- 10(-11) cm(-2) s(-1), corresponding to similar to 64\% of the flux of the Crab nebula. Results. HESS J1825-137 is a PWN with clearly energy-dependent morphology at VHE gamma-ray energies. This source is used as a laboratory to investigate particle transport within intermediate-age PWNe. Based on deep observations of this highly spatially extended PWN, we produce a spectral map of the region that provides insights into the spectral variation within the nebula.}, language = {en} } @article{SushchBrosePohl2018, author = {Sushch, Iurii and Brose, Robert and Pohl, Martin}, title = {Modeling of the spatially resolved nonthermal emission from the Vela Jr. supernova remnant}, series = {Astronomy and astrophysics : an international weekly journal}, volume = {618}, journal = {Astronomy and astrophysics : an international weekly journal}, publisher = {EDP Sciences}, address = {Les Ulis}, issn = {1432-0746}, doi = {10.1051/0004-6361/201832879}, pages = {11}, year = {2018}, abstract = {Vela Jr. (RX J0852.0-4622) is one of just a few known supernova remnants (SNRs) with a resolved shell across the whole electromagnetic spectrum from radio to very-high-energy (>100 GeV; VHE) gamma-rays. Its proximity and large size allow for detailed spatially resolved observations of the source, making Vela Jr. one of the primary sources used for the study of particle acceleration and emission mechanisms in SNRs. High-resolution X-ray observations reveal a steepening of the spectrum toward the interior of the remnant. In this study we aim for a self-consistent radiation model of Vela Jr. which at the same time would explain the broadband emission from the source and its intensity distribution. We solve the full particle transport equation combined with the high-resolution one-dimensional (1D) hydrodynamic simulations (using Pluto code) and subsequently calculate the radiation from the remnant. The equations are solved in the test particle regime. We test two models for the magnetic field profile downstream of the shock: damped magnetic field, which accounts for the damping of strong magnetic turbulence downstream, and transported magnetic field. Neither of these scenarios can fully explain the observed radial dependence of the X-ray spectrum under spherical symmetry. We show, however, that the softening of the spectrum and the X-ray intensity profile can be explained under the assumption that the emission is enhanced within a cone.}, language = {en} } @article{AbdallaAbramowskiAharonianetal.2018, author = {Abdalla, Hassan E. and Abramowski, A. and Aharonian, Felix A. and Benkhali, F. Ait and Akhperjanian, A. G. and Andersson, T. and Anguener, E. O. and Arakawa, M. and Arrieta, M. and Aubert, P. and Backes, M. and Balzer, A. and Barnard, M. and Becherini, Y. and Tjus, J. Becker and Berge, D. and Bernhard, S. and Bernloehr, K. and Blackwell, R. and Boettcher, M. and Boisson, C. and Bolmont, J. and Bordas, Pol and Bregeon, J. and Brun, F. and Brun, P. and Bryan, M. and Bilchele, M. and Bulik, T. and Capasso, M. and Carr, J. and Casanova, Sabrina and Cerruti, M. and Chakraborty, N. and Chalme-Calvet, R. and Chaves, R. C. G. and Chen, A. and Chevalier, J. and Chretien, M. and Coffaro, M. and Colafrancesco, S. and Cologna, G. and Condon, B. and Conrad, J. and Cui, Y. and Davids, I. D. and Decock, J. and Degrange, B. and Deil, C. and Devin, J. and deWilt, P. and Dirson, L. and Djannati-Atai, A. and Domainko, W. and Donath, A. and Dutson, K. and Dyks, J. and Edwards, T. and Egberts, Kathrin and Eger, P. and Ernenwein, J. -P. and Eschbach, S. and Farnier, C. and Fegan, S. and Fernandes, M. V. and Fiasson, A. and Fontaine, G. and Foerster, A. and Funk, S. and Fuessling, M. and Gabici, S. and Gajdus, M. and Gallant, Y. A. and Garrigoux, T. and Giavitto, G. and Giebels, B. and Glicenstein, J. F. and Gottschall, D. and Goya, A. and Grondin, M. -H. and Hahn, J. and Haupt, M. and Hawkes, J. and Heinzelmann, G. and Henri, G. and Hermann, G. and Hervet, O. and Hinton, J. A. and Hofmann, W. and Hoischen, Clemens and Holler, M. and Horns, D. and Ivascenko, A. and Iwasaki, H. and Jacholkowska, A. and Jamrozy, M. and Janiak, M. and Jankowsky, D. and Jankowsky, F. and Jingo, M. and Jogler, T. and Jouvin, L. and Jung-Richardt, I. and Kastendieck, M. A. and Katarzynski, K. and Katsuragawa, M. and Katz, U. and Kerszberg, D. and Khangulyan, D. and Khelifi, B. and Kieffer, M. and King, J. and Klepser, S. and Klochkov, D. and Kluzniak, W. and Kolitzus, D. and Komin, Nu. and Kosack, K. and Krakau, S. and Kraus, M. and Krueger, P. P. and Laffon, H. and Lamanna, G. and Lau, J. and Lees, J. -P. and Lefaucheur, J. and Lefranc, V. and Lemiere, A. and Lemoine-Goumard, M. and Lenain, J. -P. and Leser, Eva and Lohse, T. and Lorentz, M. and Liu, R. and Lopez-Coto, R. and Lypova, I. and Marandon, V. and Marcowith, Alexandre and Mariaud, C. and Marx, R. and Maurin, G. and Maxted, N. and Mayer, M. and Meintjes, P. J. and Meyer, M. and Mitche, A. M. W. and Moderski, R. and Mohamed, M. and Mohrmann, L. and Mora, K. and Moulin, Emmanuel and Murach, T. and Nakashima, S. and de Naurois, M. and Niederwanger, F. and Niemiec, J. and Oakes, L. and Odaka, H. and Oettl, S. and Ohm, S. and Ostrowski, M. and Oya, I. and Padovani, M. and Panter, M. and Parsons, R. D. and Arribas, M. Paz and Pekeur, N. W. and Pelletier, G. and Perennes, C. and Petrucci, P. -O. and Peyaud, B. and Piel, Q. and Pita, S. and Poon, H. and Prokhorov, D. and Prokoph, H. and Puehlhofer, G. and Punch, M. and Quirrenbach, A. and Raab, S. and Reimer, A. and Reimer, O. and Renaud, M. and de los Reyes, R. and Richter, S. and Rieger, F. and Romoli, C. and Rowell, G. and Rudak, B. and Rulten, C. B. and Sahakian, V. and Saito, S. and Salek, D. and Sanchez, D. A. and Santangelo, A. and Sasaki, M. and Schlickeiser, R. and Schuessler, F. and Schulz, A. and Schwanke, U. and Schwemmer, S. and Seglar-Arroyo, M. and Settimo, M. and Seyffert, A. S. and Shafi, N. and Shilon, I. and Simoni, R. and Sol, H. and Spanier, F. and Spengler, G. and Spies, F. and Stawarz, L. and Steenkamp, R. and Stegmann, Christian and Stycz, K. and Sushch, I. and Takahashi, T. and Tavernet, J. -P. and Tavernier, T. and Taylor, A. M. and Terrier, R. and Tibaldo, L. and Tiziani, D. and Tluczykont, M. and Trichard, C. and Tsuji, N. and Tuffs, R. and Uchiyama, Y. and van der Walt, D. J. and van Eldik, C. and van Rensburg, C. and van Soelen, B. and Vasileiadis, G. and Veh, J. and Venter, C. and Viana, A. and Vincent, P. and Vink, J. and Voisin, F. and Voelk, H. J. and Vuillaume, T. and Wadiasingh, Z. and Wagner, S. J. and Wagner, P. and Wagner, R. M. and White, R. and Wierzcholska, A. and Willmann, P. and Woernlein, A. and Wouters, D. and Yang, R. and Zabalza, V. and Zaborov, D. and Zacharias, M. and Zanin, R. and Zdziarski, A. A. and Zech, Alraune and Zefi, F. and Ziegler, A. and Zywucka, N.}, title = {Deeper HESS observations of Vela Junior (RX J0852.0-4622)}, series = {Astronomy and astrophysics : an international weekly journal}, volume = {612}, journal = {Astronomy and astrophysics : an international weekly journal}, publisher = {EDP Sciences}, address = {Les Ulis}, organization = {H E S S Collaboration}, issn = {1432-0746}, doi = {10.1051/0004-6361/201630002}, pages = {14}, year = {2018}, abstract = {Aims. We study gamma-ray emission from the shell-type supernova remnant (SNR) RXJ0852.0-4622 to better characterize its spectral properties and its distribution over the SNR. Methods. The analysis of an extended High Energy Spectroscopic System (H.E.S.S.) data set at very high energies (E > 100 GeV) permits detailed studies, as well as spatially resolved spectroscopy, of the morphology and spectrum of the whole RXJ0852.0-4622 region. The H.E.S.S. data are combined with archival data from other wavebands and interpreted in the framework of leptonic and hadronic models. The joint Fermi-LAT-H.E.S.S. spectrum allows the direct determination of the spectral characteristics of the parent particle population in leptonic and hadronic scenarios using only GeV-TeV data. Results. An updated analysis of the H.E.S.S. data shows that the spectrum of the entire SNR connects smoothly to the high-energy spectrum measured by Fermi-LAT. The increased data set makes it possible to demonstrate that the H.E.S.S. spectrum deviates significantly from a power law and is well described by both a curved power law and a power law with an exponential cutoff at an energy of E-cut = (6.7 +/- 1.2(stat) +/- 1.2(syst)) TeV. The joint Fermi-LAT-H.E.S.S. spectrum allows the unambiguous identification of the spectral shape as a power law with an exponential cutoff. No significant evidence is found for a variation of the spectral parameters across the SNR, suggesting similar conditions of particle acceleration across the remnant. A simple modeling using one particle population to model the SNR emission demonstrates that both leptonic and hadronic emission scenarios remain plausible. It is also shown that at least a part of the shell emission is likely due to the presence of a pulsar wind nebula around PSR J0855-4644.}, language = {en} } @article{AhnenAnsoldiAntonellietal.2018, author = {Ahnen, M. L. and Ansoldi, S. and Antonelli, L. A. and Arcaro, C. and Babic, A. and Banerjee, B. and Bangale, P. and Barres de Almeida, U. and Barrio, J. A. and Gonzalez, J. Becerra and Bednarek, W. and Bernardini, E. and Berti, A. and Bhattacharyya, W. and Blanch, O. and Bonnoli, G. and Carosi, R. and Carosi, A. and Chatterjee, A. and Colak, S. M. and Colin, P. and Colombo, E. and Contreras, J. L. and Cortina, J. and Covino, S. and Cumani, P. and Da Vela, P. and Dazzi, F. and De Angelis, A. and De Lotto, B. and Delfino, M. and Delgado, Jose Miguel Martins and Di Pierro, F. and Doert, M. and Dominguez, A. and Prester, D. Dominis and Doro, M. and Glawion, D. Eisenacher and Engelkemeier, M. and Ramazani, V. Fallah and Fernandez-Barral, A. and Fidalgo, D. and Fonseca, M. V. and Font, L. and Fruck, C. and Galindo, D. and Lopez, R. J. Garcia and Garczarczyk, M. and Gaug, M. and Giammaria, P. and Godinovic, N. and Gora, D. and Guberman, D. and Hadasch, D. and Hahn, A. and Hassan, T. and Hayashida, M. and Herrera, J. and Hose, J. and Hrupec, D. and Ishio, K. and Konno, Y. and Kubo, H. and Kushida, J. and Kuvezdic, D. and Lelas, D. and Lindfors, E. and Lombardi, S. and Longo, F. and Lopez, M. and Maggio, C. and Majumdar, P. and Makariev, M. and Maneva, G. and Manganaro, M. and Maraschi, L. and Mariotti, M. and Martinez, M. and Mazin, D. and Menzel, U. and Minev, M. and Miranda, J. M. and Mirzoyan, R. and Moralejo, A. and Moreno, V. and Moretti, E. and Nagayoshi, T. and Neustroev, V. and Niedzwiecki, A. and Nievas Rosillo, M. and Nigro, C. and Nilsson, K. and Ninci, D. and Nishijima, K. and Noda, K. and Nogues, L. and Paiano, S. and Palacio, J. and Paneque, D. and Paoletti, R. and Paredes, J. M. and Pedaletti, G. and Peresano, M. and Perri, L. and Persic, M. and Moroni, P. G. Prada and Prandini, E. and Puljak, I. and Garcia, J. R. and Reichardt, I. and Ribo, M. and Rico, J. and Righi, C. and Rugliancich, A. and Saito, T. and Satalecka, K. and Schroeder, S. and Schweizer, T. and Shore, S. N. and Sitarek, J. and Snidaric, I. and Sobczynska, D. and Stamerra, A. and Strzys, M. and Suric, T. and Takalo, L. and Tavecchio, F. and Temnikov, P. and Terzic, T. and Teshima, M. and Torres-Alba, N. and Treves, A. and Tsujimoto, S. and Vanzo, G. and Vazquez Acosta, M. and Vovk, I. and Ward, J. E. and Will, M. and Zaric, D. and Arbet-Engels, A. and Baack, D. and Balbo, M. and Biland, A. and Blank, M. and Bretz, T. and Bruegge, K. and Bulinski, M. and Buss, J. and Dmytriiev, A. and Dorner, D. and Einecke, S. and Elsaesser, D. and Herbst, T. and Hildebrand, D. and Kortmann, L. and Linhoff, L. and Mahlke, M. and Mannheim, K. and Mueller, S. A. and Neise, D. and Neronov, A. and Noethe, M. and Oberkirch, J. and Paravac, A. and Rhode, W. and Schleicher, B. and Schulz, F. and Sedlaczek, K. and Shukla, A. and Sliusar, V. and Walter, R. and Archer, A. and Benbow, W. and Bird, R. and Brose, Robert and Buckley, J. H. and Bugaev, V. and Christiansen, J. L. and Cui, W. and Daniel, M. K. and Falcone, A. and Feng, Q. and Finley, J. P. and Gillanders, G. H. and Gueta, O. and Hanna, D. and Hervet, O. and Holder, J. and Hughes, G. and Huetten, M. and Humensky, T. B. and Johnson, C. A. and Kaaret, P. and Kar, P. and Kelley-Hoskins, N. and Kertzman, M. and Kieda, D. and Krause, M. and Krennrich, F. and Kumar, S. and Lang, M. J. and Lin, T. T. Y. and Maier, G. and McArthur, S. and Moriarty, P. and Mukherjee, R. and Ong, R. A. and Otte, A. N. and Park, N. and Petrashyk, A. and Pichel, A. and Pohl, Martin and Quinn, J. and Ragan, K. and Reynolds, P. T. and Richards, G. T. and Roache, E. and Rovero, A. C. and Rulten, C. and Sadeh, I. and Santander, M. and Sembroski, G. H. and Shahinyan, K. and Sushch, Iurii and Tyler, J. and Wakely, S. P. and Weinstein, A. and Wells, R. M. and Wilcox, P. and Wilhel, A. and Williams, D. A. and Williamson, T. J. and Zitzer, B. and Perri, M. and Verrecchia, F. and Leto, C. and Villata, M. and Raiteri, C. M. and Jorstad, S. G. and Larionov, V. M. and Blinov, D. A. and Grishina, T. S. and Kopatskaya, E. N. and Larionova, E. G. and Nikiforova, A. A. and Morozova, D. A. and Troitskaya, Yu. V. and Troitsky, I. S. and Kurtanidze, O. M. and Nikolashvili, M. G. and Kurtanidze, S. O. and Kimeridze, G. N. and Chigladze, R. A. and Strigachev, A. and Sadun, A. C.}, title = {Extreme HBL behavior of Markarian 501 during 2012}, series = {Astronomy and astrophysics : an international weekly journal / European Southern Observatory (ESO)}, volume = {620}, journal = {Astronomy and astrophysics : an international weekly journal / European Southern Observatory (ESO)}, publisher = {EDP Sciences}, address = {Les Ulis}, organization = {MAGIC Collaboration FACT Collaboration VERITAS Collaboration}, issn = {1432-0746}, doi = {10.1051/0004-6361/201833704}, pages = {23}, year = {2018}, abstract = {Aims. We aim to characterize the multiwavelength emission from Markarian 501 (Mrk 501), quantify the energy-dependent variability, study the potential multiband correlations, and describe the temporal evolution of the broadband emission within leptonic theoretical scenarios. Methods. We organized a multiwavelength campaign to take place between March and July of 2012. Excellent temporal coverage was obtained with more than 25 instruments, including the MAGIC, FACT and VERITAS Cherenkov telescopes, the instruments on board the Swift and Fermi spacecraft, and the telescopes operated by the GASP-WEBT collaboration. Results. Mrk 501 showed a very high energy (VHE) gamma-ray flux above 0.2 TeV of similar to 0.5 times the Crab Nebula flux (CU) for most of the campaign. The highest activity occurred on 2012 June 9, when the VHE flux was similar to 3 CU, and the peak of the high-energy spectral component was found to be at similar to 2 TeV. Both the X-ray and VHE gamma-ray spectral slopes were measured to be extremely hard, with spectral indices <2 during most of the observing campaign, regardless of the X-ray and VHE flux. This study reports the hardest Mrk 501 VHE spectra measured to date. The fractional variability was found to increase with energy, with the highest variability occurring at VHE. Using the complete data set, we found correlation between the X-ray and VHE bands; however, if the June 9 flare is excluded, the correlation disappears (significance <3 sigma) despite the existence of substantial variability in the X-ray and VHE bands throughout the campaign. Conclusions. The unprecedentedly hard X-ray and VHE spectra measured imply that their low- and high-energy components peaked above 5 keV and 0.5 TeV, respectively, during a large fraction of the observing campaign, and hence that Mrk 501 behaved like an extreme high-frequency-peaked blazar (EHBL) throughout the 2012 observing season. This suggests that being an EHBL may not be a permanent characteristic of a blazar, but rather a state which may change over time. The data set acquired shows that the broadband spectral energy distribution (SED) of Mrk 501, and its transient evolution, is very complex, requiring, within the framework of synchrotron self-Compton (SSC) models, various emission regions for a satisfactory description. Nevertheless the one-zone SSC scenario can successfully describe the segments of the SED where most energy is emitted, with a significant correlation between the electron energy density and the VHE gamma-ray activity, suggesting that most of the variability may be explained by the injection of high-energy electrons. The one-zone SSC scenario used reproduces the behavior seen between the measured X-ray and VHE gamma-ray fluxes, and predicts that the correlation becomes stronger with increasing energy of the X-rays.}, language = {en} } @article{AbeysekaraArcherAuneetal.2018, author = {Abeysekara, A. U. and Archer, A. and Aune, Taylor and Benbow, Wystan and Bird, Ralph and Brose, Robert and Buchovecky, M. and Bugaev, V. and Cui, Wei and Daniel, M. K. and Falcone, A. and Feng, Qi and Finley, John P. and Fleischhack, H. and Flinders, A. and Fortson, L. and Furniss, Amy and Gotthelf, Eric V. and Grube, J. and Hanna, David and Hervet, O. and Holder, J. and Huang, K. and Hughes, G. and Humensky, T. B. and Huetten, M. and Johnson, Caitlin A. and Kaaret, Philip and Kar, P. and Kelley-Hoskins, N. and Kertzman, M. and Kieda, David and Krause, Maria and Kumar, S. and Lang, M. J. and Lin, T. T. Y. and Maier, Gernot and McArthur, S. and Moriarty, P. and Mukherjee, Reshmi and Ong, R. A. and Otte, Adam Nepomuk and Pandel, Dirk and Park, Nahee and Petrashyk, A. and Pohl, Martin and Popkow, Alexis and Pueschel, Elisa and Quinn, J. and Ragan, K. and Reynolds, P. T. and Richards, Gregory T. and Roache, E. and Rousselle, J. and Rulten, C. and Sadeh, I. and Santander, M. and Sembroski, G. H. and Shahinyan, Karlen and Tyler, J. and Vassiliev, V. V. and Wakely, S. P. and Ward, J. E. and Weinstein, A. and Wells, R. M. and Wilcox, P. and Wilhelm, Alina and Williams, David A. and Zitzer, B.}, title = {A Very High Energy gamma-Ray Survey toward the Cygnus Region of the Galaxy}, series = {The astrophysical journal : an international review of spectroscopy and astronomical physics}, volume = {861}, journal = {The astrophysical journal : an international review of spectroscopy and astronomical physics}, number = {2}, publisher = {IOP Publ. Ltd.}, address = {Bristol}, issn = {0004-637X}, doi = {10.3847/1538-4357/aac4a2}, pages = {33}, year = {2018}, abstract = {We present results from deep observations toward the Cygnus region using 300 hr of very high energy (VHE)gamma-ray data taken with the VERITAS Cerenkov telescope array and over 7 yr of high-energy.-ray data taken with the Fermi satellite at an energy above 1 GeV. As the brightest region of diffuse gamma-ray emission in the northern sky, the Cygnus region provides a promising area to probe the origins of cosmic rays. We report the identification of a potential Fermi-LAT counterpart to VER J2031+415 (TeV J2032+4130) and resolve the extended VHE source VER J2019+368 into two source candidates (VER J2018+367* and VER J2020+368*) and characterize their energy spectra. The Fermi-LAT morphology of 3FGL J2021.0+4031e (the Gamma Cygni supernova remnant) was examined, and a region of enhanced emission coincident with VER J2019+407 was identified and jointly fit with the VERITAS data. By modeling 3FGL J2015.6+3709 as two sources, one located at the location of the pulsar wind nebula CTB 87 and one at the quasar QSO J2015+371, a continuous spectrum from 1 GeV to 10 TeV was extracted for VER J2016+371 (CTB 87). An additional 71 locations coincident with Fermi-LAT sources and other potential objects of interest were tested for VHE gamma-ray emission, with no emission detected and upper limits on the differential flux placed at an average of 2.3\% of the Crab Nebula flux. We interpret these observations in a multiwavelength context and present the most detailed gamma-ray view of the region to date.}, language = {en} } @article{AbdallaAbramowskiAharonianetal.2018, author = {Abdalla, Hassan E. and Abramowski, A. and Aharonian, Felix A. and Benkhali, F. Ait and Akhperjanian, A. G. and Andersson, T. and Anguener, E. O. and Arrieta, M. and Aubert, P. and Backes, M. and Balzer, A. and Barnard, M. and Becherini, Y. and Tjus, J. Becker and Berge, D. and Bernhard, S. and Bernloehr, K. and Blackwell, R. and Boettcher, M. and Boisson, C. and Bolmont, J. and Bordas, Pol and Bregeon, J. and Brun, F. and Brun, P. and Bryan, M. and Bulik, T. and Capasso, M. and Carr, J. and Casanova, Sabrina and Cerruti, M. and Chakraborty, N. and Chalme-Calvet, R. and Chaves, R. C. G. and Chen, A. and Chevalier, J. and Chretien, M. and Colafrancesco, S. and Cologna, G. and Condon, B. and Conrad, J. and Cui, Y. and Davids, I. D. and Decock, J. and Degrange, B. and Dei, C. and Devin, J. and deWilt, P. and Dirson, L. and Djannati-Atai, A. and Domainko, W. and Donath, A. and Dubus, G. and Dutson, K. and Dyks, J. and Edwards, T. and Egberts, Kathrin and Eger, P. and Ernenwein, J. -P. and Eschbach, S. and Farnier, C. and Fegan, S. and Fernandes, M. V. and Fiasson, A. and Fontaine, G. and Foerster, A. and Fukuyama, T. and Funk, S. and Fuessling, M. and Gabici, S. and Gajdus, M. and Gallant, Y. A. and Garrigoux, T. and Giavitto, G. and Giebels, B. and Glicenstein, J. F. and Gottschall, D. and Goyal, A. and Grondin, M. -H. and Hadasch, D. and Hahn, J. and Haupt, M. and Hawkes, J. and Heinzelmann, G. and Henri, G. and Hermann, G. and Hervet, O. and Hinton, J. A. and Hofmann, W. and Hoischen, Clemens and Holler, M. and Horns, D. and Ivascenko, A. and Jacholkowska, A. and Jamrozy, M. and Janiak, M. and Jankowsky, D. and Jankowsky, F. and Jingo, M. and Jogler, T. and Jouvin, L. and Jung-Richardt, I. and Kastendieck, M. A. and Katarzynski, K. and Katz, U. and Kerszberg, D. and Khelifi, B. and Kieffer, M. and King, J. and Klepser, S. and Klochkov, D. and Kluzniak, W. and Kolitzus, D. and Komin, Nu. and Kosack, K. and Krakau, S. and Kraus, M. and Krayzel, F. and Krueger, P. P. and Laffon, H. and Lamanna, G. and Lau, J. and Lees, J. -P. and Lefaucheur, J. and Lefranc, V. and Lemiere, A. and Lemoine-Goumard, M. and Lenain, J. -P. and Leser, Eva and Lohse, T. and Lorentz, M. and Liu, R. and Lopez-Coto, R. and Lypova, I. and Marandon, V. and Marcowith, Alexandre and Mariaud, C. and Marx, R. and Maurin, G. and Maxted, N. and Mayer, M. and Meintjes, P. J. and Meyer, M. and Mitchell, A. M. W. and Moderski, R. and Mohamed, M. and Mohrmann, L. and Mora, K. and Moulin, Emmanuel and Murach, T. and de Naurois, M. and Niederwanger, F. and Niemiec, J. and Oakes, L. and Odaka, H. and Oettl, S. and Ohm, S. and Ostrowski, M. and Oya, I. and Padovani, M. and Panter, M. and Parsons, R. D. and Pekeur, N. W. and Pelletier, G. and Perennes, C. and Petrucci, P. -O. and Peyaud, B. and Piel, Q. and Pita, S. and Poon, H. and Prokhorov, D. and Prokoph, H. and Puehlhofer, G. and Punch, M. and Quirrenbach, A. and Raab, S. and Reimer, A. and Reimer, O. and Renaud, M. and de los Reyes, R. and Rieger, F. and Romoli, C. and Rosier-Lees, S. and Rowell, G. and Rudak, B. and Rulten, C. B. and Sahakian, V. and Salek, D. and Sanchez, D. A. and Santangelo, A. and Sasaki, M. and Schlickeiser, R. and Schuessler, F. and Schulz, A. and Schwanke, U. and Schwemmer, S. and Settimo, M. and Seyffert, A. S. and Shafi, N. and Shilon, I. and Simoni, R. and Sol, H. and Spanie, F. and Spengler, G. and Spies, F. and Stawarz, L. and Steenkamp, R. and Stegmann, Christian and Stinzing, F. and Stycz, K. and Sushch, I. and Takahashi, T. and Tavernet, J. -P. and Tavernier, T. and Taylor, A. M. and Terrier, R. and Tibaldo, L. and Tiziani, D. and Tluczykont, M. and Trichard, C. and Tuffs, R. and Uchiyama, Y. and van der Walt, D. J. and van Edik, C. and van Rensburg, C. and van Soelen, B. and Vasileiadis, G. and Veh, J. and Venter, C. and Viana, A. and Vincent, P. and Vink, J. and Voisin, F. and Voelk, H. J. and Volpe, F. and Vuillaume, T. and Wadiasingh, Z. and Wagner, S. J. and Wagner, P. and Wagner, R. M. and White, R. and Wierzcholska, A. and Willmann, P. and Woernlein, A. and Wouters, D. and Yang, R. and Zabalza, V. and Zaborov, D. and Zacharias, M. and Zdziarski, A. A. and Zech, Alraune and Zefi, F. and Ziegler, A. and Zywucka, N.}, title = {HESS observations of RX J1713.7-3946 with improved angular and spectral resolution}, series = {Astronomy and astrophysics : an international weekly journal}, volume = {612}, journal = {Astronomy and astrophysics : an international weekly journal}, publisher = {EDP Sciences}, address = {Les Ulis}, organization = {H E S S Collaboration}, issn = {1432-0746}, doi = {10.1051/0004-6361/201629790}, pages = {25}, year = {2018}, language = {en} } @article{WarrenEllisonBarkovetal.2017, author = {Warren, Donald C. and Ellison, Donald C. and Barkov, Maxim V. and Nagataki, Shigehiro}, title = {Nonlinear Particle Acceleration and Thermal Particles in GRB Afterglows}, series = {The astrophysical journal : an international review of spectroscopy and astronomical physics}, volume = {835}, journal = {The astrophysical journal : an international review of spectroscopy and astronomical physics}, number = {2}, publisher = {IOP Publ. Ltd.}, address = {Bristol}, issn = {0004-637X}, doi = {10.3847/1538-4357/aa56c3}, pages = {15}, year = {2017}, abstract = {The standard model for GRB afterglow emission treats the accelerated electron population as a simple power law, N(E) proportional to E-p for p greater than or similar to 2. However, in standard Fermi shock acceleration, a substantial fraction of the swept-up particles do not enter the acceleration process at all. Additionally, if acceleration is efficient, then the nonlinear back-reaction of accelerated particles on the shock structure modifies the shape of the nonthermal tail of the particle spectra. Both of these modifications to the standard synchrotron afterglow impact the luminosity, spectra, and temporal variation of the afterglow. To examine the effects of including thermal particles and nonlinear particle acceleration on afterglow emission, we follow a hydrodynamical model for an afterglow jet and simulate acceleration at numerous points during the evolution. When thermal particles are included, we find that the electron population is at no time well fitted by a single power law, though the highest-energy electrons are; if the acceleration is efficient, then the power-law region is even smaller. Our model predicts hard-soft-hard spectral evolution at X-ray energies, as well as an uncoupled X-ray and optical light curve. Additionally, we show that including emission from thermal particles has drastic effects (increases by factors of 100 and 30, respectively) on the observed flux at optical and GeV energies. This enhancement of GeV emission makes afterglow detections by future gamma-ray observatories, such as CTA, very likely.}, language = {en} } @article{DeBeckerdelValleRomeroetal.2017, author = {De Becker, M. and del Valle, Maria Victoria and Romero, G. E. and Peri, C. S. and Benaglia, P.}, title = {X- ray study of bow shocks in runaway stars}, series = {Monthly notices of the Royal Astronomical Society}, volume = {471}, journal = {Monthly notices of the Royal Astronomical Society}, publisher = {Oxford Univ. Press}, address = {Oxford}, issn = {0035-8711}, doi = {10.1093/mnras/stx1826}, pages = {4452 -- 4464}, year = {2017}, abstract = {Massive runaway stars produce bow shocks through the interaction of their winds with the interstellar medium, with the prospect for particle acceleration by the shocks. These objects are consequently candidates for non-thermal emission. Our aim is to investigate the X-ray emission from these sources. We observed with XMM-Newton a sample of five bow shock runaways, which constitutes a significant improvement of the sample of bow shock runaways studied in X-rays so far. A careful analysis of the data did not reveal any X-ray emission related to the bow shocks. However, X-ray emission from the stars is detected, in agreement with the expected thermal emission from stellar winds. On the basis of background measurements we derive conservative upper limits between 0.3 and 10 keV on the bow shocks emission. Using a simple radiation model, these limits together with radio upper limits allow us to constrain some of the main physical quantities involved in the non-thermal emission processes, such as the magnetic field strength and the amount of incident infrared photons. The reasons likely responsible for the non-detection of non-thermal radiation are discussed. Finally, using energy budget arguments, we investigate the detectability of inverse Compton X-rays in a more extended sample of catalogued runaway star bow shocks. From our analysis we conclude that a clear identification of non-thermal X-rays from massive runaway bow shocks requires one order of magnitude (or higher) sensitivity improvement with respect to present observatories.}, language = {en} } @article{KobzarNiemiecPohletal.2017, author = {Kobzar, Oleh and Niemiec, Jacek and Pohl, Martin and Bohdan, Artem}, title = {Spatio-temporal evolution of the non-resonant instability in shock precursors of young supernova remnants}, series = {Monthly notices of the Royal Astronomical Society}, volume = {469}, journal = {Monthly notices of the Royal Astronomical Society}, publisher = {Oxford Univ. Press}, address = {Oxford}, organization = {ANTARES Collaboration;H E S S Collaboration}, issn = {0035-8711}, doi = {10.1093/mnras/stx1201}, pages = {4985 -- 4998}, year = {2017}, abstract = {A non-resonant cosmic ray (CR) current-driven instability may operate in the shock precursors of young supernova remnants and be responsible for magnetic-field amplification, plasma heating and turbulence. Earlier simulations demonstrated magnetic-field amplification, and in kinetic studies a reduction of the relative drift between CRs and thermal plasma was observed as backreaction. However, all published simulations used periodic boundary conditions, which do not account for mass conservation in decelerating flows and only allow the temporal development to be studied. Here we report results of fully kinetic particle-in-cell simulations with open boundaries that permit inflow of plasma on one side of the simulation box and outflow at the other end, hence allowing an investigation of both the temporal and the spatial development of the instability. Magnetic-field amplification proceeds as in studies with periodic boundaries and, observed here for the first time, the reduction of relative drifts causes the formation of a shock-like compression structure at which a fraction of the plasma ions are reflected. Turbulent electric field generated by the non-resonant instability inelastically scatters CRs, modifying and anisotropizing their energy distribution. Spatial CR scattering is compatible with Bohm diffusion. Electromagnetic turbulence leads to significant non-adiabatic heating of the background plasma maintaining bulk equipartition between ions and electrons. The highest temperatures are reached at sites of large-amplitude electrostatic fields. Ion spectra show supra-thermal tails resulting from stochastic scattering in the turbulent electric field. Together, these modifications in the plasma flow will affect the properties of the shock and particle acceleration there.}, language = {en} } @article{BohdanNiemiecKobzaretal.2017, author = {Bohdan, Artem and Niemiec, Jacek and Kobzar, Oleh and Pohl, Martin}, title = {Electron Pre-acceleration at Nonrelativistic High-Mach-number Perpendicular Shocks}, series = {The astrophysical journal : an international review of spectroscopy and astronomical physics}, volume = {847}, journal = {The astrophysical journal : an international review of spectroscopy and astronomical physics}, publisher = {IOP Publ. Ltd.}, address = {Bristol}, issn = {0004-637X}, doi = {10.3847/1538-4357/aa872a}, pages = {17}, year = {2017}, abstract = {We perform particle-in-cell simulations of perpendicular nonrelativistic collisionless shocks to study electron heating and pre-acceleration for parameters that permit the extrapolation to the conditions at young supernova remnants. Our high-resolution large-scale numerical experiments sample a representative portion of the shock surface and demonstrate that the efficiency of electron injection is strongly modulated with the phase of the shock reformation. For plasmas with low and moderate temperature (plasma beta beta p =5.10(-4) and 0.5 beta p =), we explore the nonlinear shock structure and electron pre-acceleration for various orientations of the large-scale magnetic field with respect to the simulation plane, while keeping it at 90 degrees to the shock normal. Ion reflection off of the shock leads to the formation of magnetic filaments in the shock ramp, resulting from Weibel-type instabilities, and electrostatic Buneman modes in the shock foot. In all of the cases under study, the latter provides first-stage electron energization through the shock-surfing acceleration mechanism. The subsequent energization strongly depends on the field orientation and proceeds through adiabatic or second-order Fermi acceleration processes for configurations with the out-of-plane and in-plane field components, respectively. For strictly out-of-plane field, the fraction of suprathermal electrons is much higher than for other configurations, because only in this case are the Buneman modes fully captured by the 2D simulation grid. Shocks in plasma with moderate bp provide more efficient pre-acceleration. The relevance of our results to the physics of fully 3D systems is discussed.}, language = {en} } @article{FraschettiPohl2017, author = {Fraschetti, F. and Pohl, Martin}, title = {Particle acceleration model for the broad-band baseline spectrum of the Crab nebula}, series = {Monthly notices of the Royal Astronomical Society}, volume = {471}, journal = {Monthly notices of the Royal Astronomical Society}, publisher = {Oxford Univ. Press}, address = {Oxford}, issn = {0035-8711}, doi = {10.1093/mnras/stx1833}, pages = {4866 -- 4874}, year = {2017}, abstract = {We develop a simple one-zone model of the steady-state Crab nebula spectrum encompassing both the radio/soft X-ray and the GeV/multi-TeV observations. By solving the transport equation for GeV-TeV electrons injected at the wind termination shock as a log-parabola momentum distribution and evolved via energy losses, we determine analytically the resulting differential energy spectrum of photons. We find an impressive agreement with the observed spectrum of synchrotron emission, and the synchrotron self-Compton component reproduces the previously unexplained broad 200-GeV peak that matches the Fermi/Large Area Telescope (LAT) data beyond 1 GeV with the Major Atmospheric Gamma Imaging Cherenkov (MAGIC) data. We determine the parameters of the single log-parabola electron injection distribution, in contrast with multiple broken power-law electron spectra proposed in the literature. The resulting photon differential spectrum provides a natural interpretation of the deviation from power law customarily fitted with empirical multiple broken power laws. Our model can be applied to the radio-to-multi-TeV spectrum of a variety of astrophysical outflows, including pulsar wind nebulae and supernova remnants, as well as to interplanetary shocks.}, language = {en} } @article{NishikawaFrederiksenNordlundetal.2016, author = {Nishikawa, Ken-Ichi and Frederiksen, J. T. and Nordlund, A. and Mizuno, Y. and Hardee, P. E. and Niemiec, J. and Gomez, J. L. and Dutan, I. and Meli, A. and Sol, H. and Pohl, Martin and Hartmann, D. H.}, title = {EVOLUTION OF GLOBAL RELATIVISTIC JETS: COLLIMATIONS AND EXPANSION WITH kKHI AND THE WEIBEL INSTABILITY}, series = {The astrophysical journal : an international review of spectroscopy and astronomical physics}, volume = {820}, journal = {The astrophysical journal : an international review of spectroscopy and astronomical physics}, publisher = {IOP Publ. Ltd.}, address = {Bristol}, issn = {0004-637X}, doi = {10.3847/0004-637X/820/2/94}, pages = {14}, year = {2016}, abstract = {In the study of relativistic jets one of the key open questions is their interaction with the environment. Here. we study the initial evolution of both electron-proton (e(-) - p(+)) and electron-positron (e(+/-)) relativistic jets, focusing on their lateral interaction with ambient plasma. We follow the evolution of toroidal magnetic fields generated by both the kinetic Kelvin-Helmholtz and Mushroom instabilities. For an e(-) - p(+) jet, the induced magnetic field collimates the jet and electrons are perpendicularly accelerated. As the instabilities saturate and subsequently weaken, the magnetic polarity switches from clockwise to counterclockwise in the middle of the jet. For an e(+/-) jet, we find strong mixing of electrons and positrons with the ambient plasma, resulting in the creation of a bow shock. The merging of current filaments generates density inhomogeneities that. initiate a forward shock. Strong jet-ambient plasma mixing prevents a full development of the jet (on the scale studied), revealing evidence for both jet collimation and particle acceleration in the forming bow shock. Differences in the magnetic field structure generated by e(-) - p(+) and e(+/-) jets may contribute to the polarization properties of the observed emission in AGN jets and gamma-ray bursts.}, language = {en} } @article{ChenPohlBottcheretal.2016, author = {Chen, Xuhui and Pohl, Martin and Bottcher, Markus and Gao, Shan}, title = {Particle diffusion and localized acceleration in inhomogeneous AGN jets - II. Stochastic variation}, series = {Monthly notices of the Royal Astronomical Society}, volume = {458}, journal = {Monthly notices of the Royal Astronomical Society}, publisher = {Oxford Univ. Press}, address = {Oxford}, issn = {0035-8711}, doi = {10.1093/mnras/stw528}, pages = {3260 -- 3271}, year = {2016}, abstract = {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.}, language = {en} } @article{BroseTelezhinskyPohl2016, author = {Brose, Robert and Telezhinsky, Igor O. and Pohl, Martin}, title = {Transport of magnetic turbulence in supernova remnants}, series = {Physical review letters}, volume = {593}, journal = {Physical review letters}, publisher = {EDP Sciences}, address = {Les Ulis}, issn = {1432-0746}, doi = {10.1051/0004-6361/201527345}, pages = {8}, year = {2016}, abstract = {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.}, language = {en} } @article{PohlWilhelmTelezhinsky2015, author = {Pohl, Manuela and Wilhelm, Alina and Telezhinsky, Igor O.}, title = {Reacceleration of electrons in supernova remnants}, series = {Astronomy and astrophysics : an international weekly journal}, volume = {574}, journal = {Astronomy and astrophysics : an international weekly journal}, publisher = {EDP Sciences}, address = {Les Ulis}, issn = {0004-6361}, doi = {10.1051/0004-6361/201425027}, pages = {11}, year = {2015}, abstract = {Context. radio spectra of many shell-type supernova remnants show deviations from those expected on theoretical grounds. Aims. In this paper we determine the effect of stochastic reacceleration on the spectra of electrons in the GeV band and at lower energies, and we investigate whether reacceleration can explain the observed variation in radio spectral indices. Methods. We explicitely calculated the momentum diffusion coefficient for 3 types of turbulence expected downstream of the forward shock: fast-mode waves, small-scale non-resonant modes, and large-scale modes arising from turbulent dynamo activity. After noting that low-energy particles are efficiently coupled to the quasi-thermal plasma, a simplified cosmic-ray transport equation can be formulated and is numerically solved. Results. Only fast-mode waves can provide momentum diffusion fast enough to significantly modify the spectra of particles. Using a synchrotron emissivity that accurately reflects a highly turbulent magnetic field, we calculated the radio spectral index and find that soft spectra with index a alpha less than or similar to -0.6 can be maintained over more than 2 decades in radio frequency, even if the electrons experience reacceleration for only one acceleration time. A spectral hardening is possible but considerably more frequency-dependent. The spectral modification imposed by stochastic reacceleration downstream of the forward shock depends only weakly on the initial spectrum provided by, e.g., diffusive shock acceleration at the shock itself.}, language = {en} } @article{ChenPohlBoettcher2015, author = {Chen, Xuhui and Pohl, Martin and B{\"o}ttcher, Markus}, title = {Particle diffusion and localized acceleration in inhomogeneous AGN jets - I. Steady-state spectra}, series = {Monthly notices of the Royal Astronomical Society}, volume = {447}, journal = {Monthly notices of the Royal Astronomical Society}, number = {1}, publisher = {Oxford Univ. Press}, address = {Oxford}, issn = {0035-8711}, doi = {10.1093/mnras/stu2438}, pages = {530 -- 544}, year = {2015}, abstract = {We study the acceleration, transport, and emission of particles in relativistic jets. Localized stochastic particle acceleration, spatial diffusion, and synchrotron as well as synchrotron self-Compton (SSC) emission are considered in a leptonic model. To account for inhomogeneity, we use a 2D axisymmetric cylindrical geometry for both relativistic electrons and magnetic field. In this first phase of our work, we focus on steady-state spectra that develop from a time-dependent model. We demonstrate that small isolated acceleration region in a much larger emission volume are sufficient to accelerate particles to high energy. Diffusive escape from these small regions provides a natural explanation for the spectral form of the jet emission. The location of the acceleration regions within the jet is found to affect the cooling break of the spectrum in this diffusive model. Diffusion-caused energy-dependent inhomogeneity in the jets predicts that the SSC spectrum is harder than the synchrotron spectrum. There can also be a spectral hardening towards the high-energy section of the synchrotron spectrum, if particle escape is relatively slow. These two spectral hardening effects indicate that the jet inhomogeneity might be a natural explanation for the unexpected hard. gamma-ray spectra observed in some blazars.}, language = {en} } @article{AbramowskiAharonianBenkhalietal.2015, author = {Abramowski, Attila and Aharonian, Felix A. and Benkhali, Faical Ait and Akhperjanian, A. G. and Ang{\"u}ner, Ekrem Oǧuzhan and Backes, Michael and Balzer, Arnim and Becherini, Yvonne and Tjus, J. Becker and Berge, David and Bernhard, Sabrina and Bernl{\"o}hr, K. and Birsin, E. and Blackwell, R. and Boettcher, Markus and Boisson, Catherine and Bolmont, J. and Bordas, Pol and Bregeon, Johan and Brun, Francois and Brun, Pierre and Bryan, Mark and Bulik, Tomasz and Carr, John and Casanova, Sabrina and Chakraborty, N. and Chalme-Calvet, R. and Chaves, Ryan C. G. and Chen, Andrew and Chretien, M. and Colafrancesco, Sergio and Cologna, Gabriele and Conrad, Jan and Couturier, C. and Cui, Y. and Davids, I. D. and Degrange, B. and Deil, C. and deWilt, P. and Djannati-Ata{\"i}, A. and Domainko, W. and Donath, A. and Dubus, G. and Dutson, K. and Dyks, J. and Dyrda, M. and Edwards, T. and Egberts, Kathrin and Eger, P. and Ernenwein, J. -P. and Espigat, P. and Farnier, C. and Fegan, S. and Feinstein, F. and Fernandesl, M. V. and Fernandez, D. and Fiasson, A. and Fontaine, G. and Foerster, A. and Fuessling, M. and Gabici, S. and Gajdus, M. and Gallant, Y. A. and Garrigoux, T. and Giavitto, G. and Giebels, B. and Glicenstein, J. F. and Gottschall, D. and Goyal, A. and Grondin, M. -H. and Grudzinska, M. and Hadasch, D. and Haeffner, S. and Hahn, J. and Hawkes, J. and Heinzelmann, G. and Henri, G. and Hermann, G. and Hervet, O. and Hillert, A. and Hinton, James Anthony and Hofmann, W. and Hofverberg, P. and Hoischen, Clemens and Holler, M. and Horns, D. and Ivascenko, A. and Jacholkowska, A. and Jahn, C. and Jamrozy, M. and Janiak, M. and Jankowsky, F. and Jung-Richardt, I. and Kastendieckl, M. A. and Katarzynski, K. and Katz, U. and Kerszberg, D. and Khelifi, B. and Kieffer, M. and Klepser, S. and Klochkov, D. and Kluzniak, W. and Kolitzus, D. and Komin, Nu. and Kosack, K. and Krakau, S. and Krayzel, F. and Krueger, P. P. and Laffon, H. and Lamanna, G. and Lau, J. and Lefaucheur, J. and Lefranc, V. and Lemiere, A. and Lemoine-Goumard, M. and Lenain, J. -P. and Lohse, T. and Lopatin, A. and Lu, C. -C. and Lui, R. and Marandon, V. and Marcowith, Alexandre and Mariaud, C. and Marx, R. and Maurin, G. and Maxted, N. and Mayer, M. and Meintjes, P. J. and Menzler, U. and Meyer, M. and Mitchell, A. M. W. and Moderski, R. and Mohamed, M. and Mora, K. and Moulin, Emmanuel and Murach, T. and de Naurois, M. and Niemiec, J. and Oakes, L. and Odaka, H. and Oettl, S. and Ohm, S. and de Ona Wilhelmi, E. and Opitz, B. and Ostrowski, M. and Oya, I. and Panter, M. and Parsons, R. D. and Arribas, M. Paz and Pekeur, N. W. and Pelletier, G. and Petrucci, P. -O. and Peyaud, B. and Pita, S. and Poon, H. and Prokoph, H. and Puehlhofer, G. and Punch, M. and Quirrenbach, A. and Raab, S. and Reichardt, I. and Reimer, A. and Reimer, O. and Renaud, M. and de los Reyes, R. and Rieger, F. and Romoli, C. and Rosier-Lees, S. and Rowell, G. and Rudak, B. and Rulten, C. B. and Sahakian, V. and Salek, D. and Sanchez, David M. and Santangelo, A. and Sasaki, M. and Schlickeiser, R. and Schuessler, F. and Schulz, A. and Schwanke, U. and Schwemmer, S. and Seyffert, A. S. and Simoni, R. and Sol, H. and Spanier, F. and Spengler, G. and Spies, F. and Stawarz, L. and Steenkamp, R. and Stegmann, Christian and Stinzing, F. and Stycz, K. and Sushch, Iurii and Tavernet, J. -P. and Tavernier, T. and Taylor, A. M. and Terrier, R. and Tluczykont, M. and Trichard, C. and Valerius, K. and van der Walt, J. and van Eldik, C. and van Soelen, B. and Vasileiadis, G. and Veh, J. and Venter, C. and Viana, A. and Vincent, P. and Vink, J. and Voisin, F. and Voelk, H. J. and Vuillaume, T. and Wagner, S. J. and Wagner, P. and Wagner, R. M. and Weidinger, M. and Weitzel, Q. and White, R. and Wierzcholska, A. and Willmann, P. and Woernlein, A. and Wouters, D. and Yang, R. and Zabalza, V. and Zaborov, D. and Zacharias, M. and Zdziarski, A. A. and Zech, Alraune and Zefi, F. and Zywucka, N.}, title = {Discovery of variable VHE gamma-ray emission from the binary system 1FGL J1018.6-5856}, series = {Astronomy and astrophysics : an international weekly journal}, volume = {577}, journal = {Astronomy and astrophysics : an international weekly journal}, publisher = {EDP Sciences}, address = {Les Ulis}, organization = {HESS Collaboration}, issn = {0004-6361}, doi = {10.1051/0004-6361/201525699}, pages = {6}, year = {2015}, abstract = {Re-observations with the HESS telescope array of the very high-energy (VHE) source HESS J1018-589A that is coincident with the Fermi-LAT gamma-ray binary 1FGL J1018.6-5856 have resulted in a source detection significance of more than 9 sigma and the detection of variability (chi(2)/nu of 238.3/155) in the emitted gamma-ray flux. This variability confirms the association of HESS J1018-589A with the high-energy gamma-ray binary detected Fermi-LAT and also confirms the point-like source as a new VHE binary system. The spectrum of HESS J1018-589A is best fit with a power-law function with photon index Gamma = 2.20 +/- 0.14(stat) +/- 0.2(sys). Emission is detected up to similar to 20 TeV. The mean differential flux level is (2.9 +/- 0.4) x 10(-13) TeV-1 cm(-2) s(-1) at 1 TeV, equivalent to similar to 1\% of the flux from the Crab Nebula at the same energy. Variability is clearly detected the night-by-night light curve. When folded on the orbital period of 16.58 days, the rebinned light curve peaks in phase with the observed X-ray high-energy phaseograms. The fit of the HESS phaseogram to a constant flux provides evidence of periodicity at the level of N-sigma > 3 sigma. The of the VHE phaseogram and measured spectrum suggest a low-inclination, low-eccentricity system with a modest impact from VHE gamma-ray due to pair production (tau less than or similar to 1 at 300 GeV).}, language = {en} } @article{AbramowskiAharonianBenkhalietal.2015, author = {Abramowski, Attila and Aharonian, Felix A. and Benkhali, Faical Ait and Akhperjanian, A. G. and Ang{\"u}ner, Ekrem Oǧuzhan and Backes, Michael and Balenderan, Shangkari and Balzer, Arnim and Barnacka, Anna and Becherini, Yvonne and Tjus, J. Becker and Berge, David and Bernhard, Sabrina and Bernl{\"o}hr, K. and Birsin, E. and Biteau, Jonathan and Boettcher, Markus and Boisson, Catherine and Bolmont, J. and Bordas, Pol and Bregeon, Johan and Brun, Francois and Brun, Pierre and Bryan, Mark and Bulik, Tomasz and Carrigan, Svenja and Casanova, Sabrina and Chadwick, Paula M. and Chakraborty, N. and Chalme-Calvet, R. and Chaves, Ryan C. G. and Chretien, M. and Colafrancesco, Sergio and Cologna, Gabriele and Conrad, Jan and Couturier, C. and Cui, Y. and Davids, I. D. and Degrange, B. and Deil, C. and deWilt, P. and Djannati-Ata{\"i}, A. and Domainko, W. and Donath, A. and Dubus, G. and Dutson, K. and Dyks, J. and Dyrda, M. and Edwards, T. and Egberts, Kathrin and Eger, P. and Espigat, P. and Farnier, C. and Fegan, S. and Feinstein, F. and Fernandes, M. V. and Fernandez, D. and Fiasson, A. and Fontaine, G. and Foerster, A. and F{\"u}ssling, Matthias and Gabici, S. and Gajdus, M. and Gallant, Y. A. and Garrigoux, T. and Giavitto, G. and Giebels, B. and Glicenstein, J. F. and Gottschall, D. and Grondin, M. -H. and Grudzinska, M. and Hadasch, D. and Haeffner, S. and Hahn, J. and Harris, J. and Heinzelmann, G. and Henri, G. and Hermann, G. and Hervet, O. and Hillert, A. and Hinton, James Anthony and Hofmann, W. and Hofverberg, P. and Holler, Maraike and Horns, D. and Ivascenko, A. and Jacholkowska, A. and Jahn, C. and Jamrozy, M. and Janiak, M. and Jankowsky, F. and Jung-Richardt, I. and Kastendieck, M. A. and Katarzynski, K. and Katz, U. and Kaufmann, S. and Khelifi, B. and Kieffer, M. and Klepser, S. and Klochkov, D. and Kluzniak, W. and Kolitzus, D. and Komin, Nu. and Kosack, K. and Krakau, S. and Krayzel, F. and Krueger, P. P. and Laffon, H. and Lamanna, G. and Lefaucheur, J. and Lefranc, V. and Lemiere, A. and Lemoine-Goumard, M. and Lenain, J. -P. and Lohse, T. and Lopatin, A. and Lu, C. -C. and Marandon, V. and Marcowith, Alexandre and Marx, R. and Maurin, G. and Maxted, N. and Mayer, Michael and McComb, T. J. L. and Mehault, J. and Meintjes, P. J. and Menzler, U. and Meyer, M. and Mitchell, A. M. W. and Moderski, R. and Mohamed, M. and Mora, K. and Moulin, Emmanuel and Murach, T. and de Naurois, M. and Niemiec, J. and Nolan, S. J. and Oakes, L. and Odaka, H. and Ohm, S. and Opitz, B. and Ostrowski, M. and Oya, I. and Panter, M. and Parsons, R. D. and Arribas, M. Paz and Pekeur, N. W. and Pelletier, G. and Petrucci, P. -O and Peyaud, B. and Pita, S. and Poon, H. and Puehlhofer, G. and Punch, M. and Quirrenbach, A. and Raab, S. and Reichardt, I. and Reimer, A. and Reimer, O. and Renaud, M. and de los Reyes, R. and Rieger, F. and Romoli, C. and Rosier-Lees, S. and Rowell, G. and Rudak, B. and Rulten, C. B. and Sahakian, V. and Salek, D. and Sanchez, David M. and Santangelo, A. and Schlickeiser, R. and Schuessler, F. and Schulz, A. and Schwanke, U. and Schwarzburg, S. and Schwemmer, S. and Sol, H. and Spanier, F. and Spengler, G. and Spies, F. and Stawarz, L. and Steenkamp, R. and Stegmann, Christian and Stinzing, F. and Stycz, K. and Sushch, Iurii and Tavernet, J. -P. and Tavernier, T. and Taylor, A. M. and Terrier, R. and Tluczykont, M. and Trichard, C. and Valerius, K. and van Eldik, C. and van Soelen, B. and Vasileiadis, G. and Veh, J. and Venter, C. and Viana, A. and Vincent, P. and Vink, J. and Voelk, H. J. and Volpe, F. and Vorster, M. and Vuillaume, T. and Wagner, S. J. and Wagner, P. and Wagner, R. M. and Ward, M. and Weidinger, M. and Weitzel, Q. and White, R. and Wierzcholska, A. and Willmann, P. and Woernlein, A. and Wouters, D. and Yang, R. and Zabalza, V. and Zaborov, D. and Zacharias, M. and Zdziarski, A. A. and Zech, Alraune and Zechlin, H. -S.}, title = {HESS reveals a lack of TeV emission from the supernova remnant Puppis A (Research Note)}, series = {Astronomy and astrophysics : an international weekly journal}, volume = {575}, journal = {Astronomy and astrophysics : an international weekly journal}, publisher = {EDP Sciences}, address = {Les Ulis}, organization = {HESS Collaboration}, issn = {0004-6361}, doi = {10.1051/0004-6361/2014424805}, pages = {6}, year = {2015}, abstract = {Context. Puppis A is an interesting similar to 4 kyr-old supernova remnant (SNR) that shows strong evidence of interaction between the forward shock and a molecular cloud. It has been studied in detail from radio frequencies to high-energy (HE, 0.1-100 GeV) gamma-rays. An analysis of the Fermi-LAT data has shown extended HE gamma-ray emission with a 0.2-100 GeV spectrum exhibiting no significant deviation from a power law, unlike most of the GeV-emitting SNRs known to be interacting with molecular clouds. This makes it a promising target for imaging atmospheric Cherenkov telescopes (IACTs) to probe the gamma-ray emission above 100 GeV. Aims. Very-high-energy (VHE, E >= 0.1 TeV) gamma-ray emission from Puppis A has been, for the first time, searched for with the High Energy Stereoscopic System (HESS.). Methods. Stereoscopic imaging of Cherenkov radiation from extensive air showers is used to reconstruct the direction and energy of the incident gamma-rays in order to produce sky images and source spectra. The profile likelihood method is applied to find constraints on the existence of a potential break or cutoff in the photon spectrum. Results. The analysis of the HESS. data does not reveal any significant emission towards Puppis A. The derived upper limits on the differential photon flux imply that its broadband gamma-ray spectrum must exhibit a spectral break or cutoff. By combining Fermi-LAT and HESS. measurements, the 99\% confidence-level upper limits on such a cutoff are found to be 450 and 280 GeV, assuming a power law with a simple exponential and a sub-exponential cutoff, respectively. It is concluded that none of the standard limitations (age, size, radiative losses) on the particle acceleration mechanism, assumed to be continuing at present, can explain the lack of VHE signal. The scenario in which particle acceleration has ceased some time ago is considered as an alternative explanation. The HE/VHE spectrum of Puppis A could then exhibit a break of non-radiative origin (as observed in several other interacting SNRs, albeit at somewhat higher energies), owing to the interaction with dense and neutral material, in particular towards the NE region.}, language = {en} } @article{AbramowskiAharonianBenkhalietal.2015, author = {Abramowski, Attila and Aharonian, Felix A. and Benkhali, Faical Ait and Akhperjanian, A. G. and Ang{\"u}ner, Ekrem Oǧuzhan and Anton, Gisela and Backes, Michael and Balenderan, Shangkari and Balzer, Arnim and Barnacka, Anna and Becherini, Yvonne and Tjus, J. Becker and Bernl{\"o}hr, K. and Birsin, E. and Bissaldi, E. and Biteau, Jonathan and Boettcher, Markus and Boisson, Catherine and Bolmont, J. and Bordas, Pol and Brucker, J. and Brun, Francois and Brun, Pierre and Bulik, Tomasz and Carrigan, Svenja and Casanova, Sabrina and Chadwick, Paula M. and Chalme-Calvet, R. and Chaves, Ryan C. G. and Cheesebrough, A. and Chretien, M. and Colafrancesco, Sergio and Cologna, Gabriele and Conrad, Jan and Couturier, C. and Cui, Y. and Dalton, M. and Daniel, M. K. and Davids, I. D. and Degrange, B. and Deil, C. and deWilt, P. and Dickinson, H. J. and Djannati-Ata{\"i}, A. and Domainko, W. and Dubus, G. and Dutson, K. and Dyks, J. and Dyrda, M. and Edwards, T. and Egberts, Kathrin and Eger, P. and Espigat, P. and Farnier, C. and Fegan, S. and Feinstein, F. and Fernandes, M. V. and Fernandez, D. and Fiasson, A. and Fontaine, G. and Foerster, A. and F{\"u}ßling, Matthias and Gajdus, M. and Gallant, Y. A. and Garrigoux, T. and Giavitto, G. and Giebels, B. and Glicenstein, J. F. and Grondin, M. -H. and Grudzinska, M. and Haeffner, S. and Hahn, J. and Harris, J. and Heinzelmann, G. and Henri, G. and Hermann, G. and Hervet, O. and Hillert, A. and Hinton, James Anthony and Hofmann, W. and Hofverberg, P. and Holler, Markus and Horns, D. and Jacholkowska, A. and Jahn, C. and Jamrozy, M. and Janiak, M. and Jankowsky, F. and Jung, I. and Kastendieck, M. A. and Katarzynski, K. and Katz, U. and Kaufmann, S. and Khelifi, B. and Kieffer, M. and Klepser, S. and Klochkov, D. and Kluzniak, W. and Kneiske, T. and Kolitzus, D. and Komin, Nu. and Kosack, K. and Krakau, S. and Krayzel, F. and Krueger, P. P. and Laffon, H. and Lamanna, G. and Lefaucheur, J. and Lemiere, A. and Lemoine-Goumard, M. and Lenain, J. -P. and Lohse, T. and Lopatin, A. and Lu, C. -C. and Marandon, V. and Marcowith, Alexandre and Marx, R. and Maurin, G. and Maxted, N. and Mayer, Markus and McComb, T. J. L. and Mehault, J. and Meintjes, P. J. and Menzler, U. and Meyer, M. and Moderski, R. and Mohamed, M. and Moulin, Emmanuel and Murach, T. and Naumann, C. L. and de Naurois, M. and Niemiec, J. and Nolan, S. J. and Oakes, L. and Odaka, H. and Ohm, S. and Wilhelmi, E. de Ona and Opitz, B. and Ostrowski, M. and Oya, I. and Panter, M. and Parsons, R. D. and Arribas, M. Paz and Pekeur, N. W. and Pelletier, G. and Perez, J. and Petrucci, P. -O. and Peyaud, B. and Pita, S. and Poon, H. and Puehlhofer, G. and Punch, M. and Quirrenbach, A. and Raab, S. and Raue, M. and Reichardt, I. and Reimer, A. and Reimer, O. and Renaud, M. and Reyes, R. de los and Rieger, F. and Rob, L. and Romoli, C. and Rosier-Lees, S. and Rowell, G. and Rudak, B. and Rulten, C. B. and Sahakian, V. and Sanchez, David M. and Santangelo, A. and Schlickeiser, R. and Schuessler, F. and Schulz, A. and Schwanke, U. and Schwarzburg, S. and Schwemmer, S. and Sol, H. and Spengler, G. and Spies, F. and Stawarz, L. and Steenkamp, R. and Stegmann, Christian and Stinzing, F. and Stycz, K. and Sushch, Iurii and Tavernet, J. -P. and Tavernier, T. and Taylor, A. M. and Terrier, R. and Tluczykont, M. and Trichard, C. and Valerius, K. and van Eldik, C. and van Soelen, B. and Vasileiadis, G. and Venter, C. and Viana, A. and Vincent, P. and Voelk, H. J. and Volpe, F. and Vorster, M. and Vuillaume, T. and Wagner, S. J. and Wagner, P. and Wagner, R. M. and Ward, M. and Weidinger, M. and Weitzel, Q. and White, R. and Wierzcholska, A. and Willmann, P. and Woernlein, A. and Wouters, D. and Yang, R. and Zabalza, V. and Zacharias, M. and Zdziarski, A. A. and Zech, Alraune and Zechlin, H. -S. and Acero, F. and Casandjian, J. M. and Cohen-Tanugi, J. and Giordano, F. and Guillemot, L. and Lande, J. and Pletsch, H. and Uchiyama, Y.}, title = {Probing the gamma-ray emission from HESS J1834-087 using HESS and Fermi LAT observations}, series = {Astronomy and astrophysics : an international weekly journal}, volume = {574}, journal = {Astronomy and astrophysics : an international weekly journal}, publisher = {EDP Sciences}, address = {Les Ulis}, organization = {HESS Collaboration, Fermi-LAT Collaboration}, issn = {0004-6361}, doi = {10.1051/0004-6361/201322694}, pages = {10}, year = {2015}, abstract = {Aims. Previous observations with the High Energy Stereoscopic System (H.E.S.S.) have revealed an extended very-high-energy (VHE; E > 100 GeV) gamma-ray source, HESS J1834-087, coincident with the supernova remnant (SNR) W41. The origin of the gamma-ray emission was investigated in more detail with the H.E.S.S. array and the Large Area Telescope (LAT) onboard the Fermi Gamma-ray Space Telescope. Methods. The gamma-ray data provided by 61 h of observations with H.E.S.S., and four years with the Fermi LAT were analyzed, covering over five decades in energy from 1.8 GeV up to 30 TeV. The morphology and spectrum of the TeV and GeV sources were studied and multiwavelength data were used to investigate the origin of the gamma-ray emission toward W41. Results. The TeV source can be modeled with a sum of two components: one point-like and one significantly extended (sigma(TeV) = 0.17 degrees +/- 0.01 degrees), both centered on SNR W41 and exhibiting spectra described by a power law with index Gamma(TeV) similar or equal to 2.6. The GeV source detected with Fermi LAT is extended (sigma(GeV) = 0.15 degrees +/- 0.03 degrees) and morphologically matches the VHE emission. Its spectrum can be described by a power-law model with an index Gamma(GeV) = 2.15 +/- 0.12 and smoothly joins the spectrum of the whole TeV source. A break appears in the gamma-ray spectra around 100 GeV. No pulsations were found in the GeV range. Conclusions. Two main scenarios are proposed to explain the observed emission: a pulsar wind nebula (PWN) or the interaction of SNR W41 with an associated molecular cloud. X-ray observations suggest the presence of a point-like source (a pulsar candidate) near the center of the remnant and nonthermal X-ray diffuse emission that could arise from the possibly associated PWN. The PWN scenario is supported by the compatible positions of the TeV and GeV sources with the putative pulsar. However, the spectral energy distribution from radio to gamma-rays is reproduced by a one-zone leptonic model only if an excess of low-energy electrons is injected following a Maxwellian distribution by a pulsar with a high spin-down power (> 10(37) erg s(-1)). This additional low-energy component is not needed if we consider that the point-like TeV source is unrelated to the extended GeV and TeV sources. The interacting SNR scenario is supported by the spatial coincidence between the gamma-ray sources, the detection of OH (1720 MHz) maser lines, and the hadronic modeling.}, language = {en} } @article{NishikawaHardeeDutanetal.2014, author = {Nishikawa, Ken-Ichi and Hardee, P. E. and Dutan, I. and Niemiec, J. and Medvedev, M. and Mizuno, Y. and Meli, A. and Sol, H. and Zhang, B. and Pohl, Martin and Hartmann, D. H.}, title = {Magnetic agnetic field generation in core-sheath jets via the kinetic Kelvin-Helmholtz instability}, series = {The astrophysical journal : an international review of spectroscopy and astronomical physics}, volume = {793}, journal = {The astrophysical journal : an international review of spectroscopy and astronomical physics}, number = {1}, publisher = {IOP Publ. Ltd.}, address = {Bristol}, issn = {0004-637X}, doi = {10.1088/0004-637X/793/1/60}, pages = {16}, year = {2014}, abstract = {We have investigated magnetic field generation in velocity shears via the kinetic Kelvin-Helmholtz instability (kKHI) using a relativistic plasma jet core and stationary plasma sheath. Our three-dimensional particle-in-cell simulations consider plasma jet cores with Lorentz factors of 1.5, 5, and 15 for both electron-proton and electron-positron plasmas. For electron-proton plasmas, we find generation of strong large-scale DC currents and magnetic fields that extend over the entire shear surface and reach thicknesses of a few tens of electron skin depths. For electron-positron plasmas, we find generation of alternating currents and magnetic fields. Jet and sheath plasmas are accelerated across the shear surface in the strong magnetic fields generated by the kKHI. The mixing of jet and sheath plasmas generates a transverse structure similar to that produced by the Weibel instability.}, language = {en} } @article{AliuArchambaultAuneetal.2014, author = {Aliu, E. and Archambault, S. and Aune, T. and Behera, B. and Beilicke, M. and Benbow, W. and Berger, K. and Bird, R. and Bouvier, A. and Buckley, J. H. and Bugaev, V. and Byrum, K. and Cerruti, M. and Chen, X. and Ciupik, L. and Connolly, M. P. and Cui, W. and Duke, C. and Dumm, J. and Errando, M. and Falcone, A. and Federici, S. and Feng, Q. and Finley, J. P. and Fortin, P. and Fortson, L. and Furniss, A. and Galante, N. and Gillanders, G. H. and Griffin, S. and Griffiths, S. T. and Grube, J. and Gyuk, G. and Hanna, D. and Holder, J. and Hughes, G. and Humensky, T. B. and Kaaret, P. and Kertzman, M. and Khassen, Y. and Kieda, D. and Krawczynski, H. and Krennrich, F. and Lang, M. J. and Madhavan, A. S. and Maier, G. and Majumdar, P. and McCann, A. and Moriarty, P. and Mukherjee, R. and Nieto, D. and Ong, R. A. and Otte, A. N. and Park, N. and Perkins, J. S. and Pohl, M. and Popkow, A. and Prokoph, H. and Quinn, J. and Ragan, K. and Rajotte, J. and Reyes, L. C. and Reynolds, P. T. and Richards, G. T. and Roache, E. and Rousselle, J. and Sembroski, G. H. and Sheidaei, F. and Skole, C. and Smith, A. W. and Staszak, D. and Stroh, M. and Telezhinsky, Igor O. and Theiling, M. and Tucci, J. V. and Tyler, J. and Varlotta, A. and Vincent, S. and Wakely, S. P. and Weinstein, A. and Welsing, R. and Williams, D. A. and Zajczyk, A. and Zitzer, B. and Abramowski, Attila and Aharonian, Felix A. and Benkhali, Faical Ait and Akhperjanian, A. G. and Ang{\"u}ner, Ekrem Oǧuzhan and Anton, Gisela and Balenderan, Shangkari and Balzer, Arnim and Barnacka, Anna and Becherini, Yvonne and Tjus, J. Becker and Bernl{\"o}hr, K. and Birsin, E. and Bissaldi, E. and Biteau, Jonathan and Boettcher, Markus and Boisson, Catherine and Bolmont, J. and Bordas, Pol and Brucker, J. and Brun, Francois and Brun, Pierre and Bulik, Tomasz and Carrigan, Svenja and Casanova, Sabrina and Cerruti, M. and Chadwick, Paula M. and Chalme-Calvet, R. and Chaves, Ryan C. G. and Cheesebrough, A. and Chretien, M. and Colafrancesco, Sergio and Cologna, Gabriele and Conrad, Jan and Couturier, C. and Dalton, M. and Daniel, M. K. and Davids, I. D. and Degrange, B. and Deil, C. and deWilt, P. and Dickinson, H. J. and Djannati-Ata{\"i}, A. and Domainko, W. and Dubus, G. and Dutson, K. and Dyks, J. and Dyrda, M. and Edwards, T. and Egberts, Kathrin and Eger, P. and Espigat, P. and Farnier, C. and Fegan, S. and Feinstein, F. and Fernandes, M. V. and Fernandez, D. and Fiasson, A. and Fontaine, G. and Foerster, A. and Fuessling, M. and Gajdus, M. and Gallant, Y. A. and Garrigoux, T. and Giavitto, G. and Giebels, B. and Glicenstein, J. F. and Grondin, M. -H. and Grudzinska, M. and Haeffner, S. and Hahn, J. and Harris, J. and Heinzelmann, G. and Henri, G. and Hermann, G. and Hervet, O. and Hillert, A. and Hinton, James Anthony and Hofmann, W. and Hofverberg, P. and Holler, M. and Horns, D. and Jacholkowska, A. and Jahn, C. and Jamrozy, M. and Janiak, M. and Jankowsky, F. and Jung, I. and Kastendieck, M. A. and Katarzynski, K. and Katz, U. and Kaufmann, S. and Khelifi, B. and Kieffer, M. and Klepser, S. and Klochkov, D. and Kluzniak, W. and Kneiske, T. and Kolitzus, D. and Komin, Nu. and Kosack, K. and Krakau, S. and Krayzel, F. and Krueger, P. P. and Laffon, H. and Lamanna, G. and Lefaucheur, J. and Lemiere, A. and Lemoine-Goumard, M. and Lenain, J. -P. and Lennarz, D. and Lohse, T. and Lopatin, A. and Lu, C. -C. and Marandon, V. and Marcowith, Alexandre and Marx, R. and Maurin, G. and Maxted, N. and Mayer, M. and McComb, T. J. L. and Mehault, J. and Menzler, U. and Meyer, M. and Moderski, R. and Mohamed, M. and Moulin, Emmanuel and Murach, T. and Naumann, C. L. and de Naurois, M. and Niemiec, J. and Nolan, S. J. and Oakes, L. and Ohm, S. and Wilhelmi, E. de Ona and Opitz, B. and Ostrowski, M. and Oya, I. and Panter, M. and Parsons, R. D. and Arribas, M. Paz and Pekeur, N. W. and Pelletier, G. and Perez, J. and Petrucci, P. -O. and Peyaud, B. and Pita, S. and Poon, H. and Puehlhofer, G. and Punch, M. and Quirrenbach, A. and Raab, S. and Raue, M. and Reimer, A. and Reimer, O. and Renaud, M. and de los Reyes, R. and Rieger, F. and Rob, L. and Romoli, C. and Rosier-Lees, S. and Rowell, G. and Rudak, B. and Rulten, C. B. and Sahakian, V. and Sanchez, David M. and Santangelo, A. and Schlickeiser, R. and Schuessler, F. and Schulz, A. and Schwanke, U. and Schwarzburg, S. and Schwemmer, S. and Sol, H. and Spengler, G. and Spies, F. and Stawarz, L. and Steenkamp, R. and Stegmann, Christian and Stinzing, F. and Stycz, K. and Sushch, Iurii and Szostek, A. and Tavernet, J. -P. and Tavernier, T. and Taylor, A. M. and Terrier, R. and Tluczykont, M. and Trichard, C. and Valerius, K. and van Eldik, C. and Vasileiadis, G. and Venter, C. and Viana, A. and Vincent, P. and Voelk, H. J. and Volpe, F. and Vorster, M. and Wagner, S. J. and Wagner, P. and Ward, M. and Weidinger, M. and Weitzel, Q. and White, R. and Wierzcholska, A. and Willmann, P. and Woernlein, A. and Wouters, D. and Zacharias, M. and Zajczyk, A. and Zdziarski, A. A. and Zech, Alraune and Zechlin, H. -S.}, title = {Long-term TeV and X-RAY observations of the GAMMA- RAY binary hess J0632+057}, series = {The astrophysical journal : an international review of spectroscopy and astronomical physics}, volume = {780}, journal = {The astrophysical journal : an international review of spectroscopy and astronomical physics}, number = {2}, publisher = {IOP Publ. Ltd.}, address = {Bristol}, organization = {VERITAS Collaboration, HESS Collaboration}, issn = {0004-637X}, doi = {10.1088/0004-637X/780/2/168}, pages = {14}, year = {2014}, language = {en} } @article{AliuArchambaultBeheraetal.2013, author = {Aliu, E. and Archambault, S. and Behera, B. and Berger, K. and Beilicke, M. and Benbow, W. and Bird, R. and Bouvier, A. and Bugaev, V. and Cerruti, M. and Chen, Xuhui and Ciupik, L. and Connolly, M. P. and Cui, W. and Dumm, J. and Falcone, A. and Federici, Simone and Feng, Q. and Finley, J. P. and Fortin, P. and Fortson, L. and Furniss, A. and Galante, N. and Gillanders, G. H. and Griffin, S. and Griffiths, S. T. and Grube, J. and Gyuk, G. and Hanna, D. and Holder, J. and Hughes, G. and Humensky, T. B. and Kaaret, P. and Kertzman, M. and Khassen, Y. and Kieda, D. and Krennrich, F. and Lang, M. J. and Maier, G. and Majumdar, P. and McArthur, S. and McCann, A. and Moriarty, P. and Mukherjee, R. and de Bhroithe, A. O'Faolain and Ong, R. A. and Otte, A. N. and Park, N. and Perkins, J. S. and Pohl, Martin and Popkow, A. and Prokoph, H. and Quinn, J. and Ragan, K. and Rajotte, J. and Ratliff, G. and Reynolds, P. T. and Richards, G. T. and Roache, E. and Sembroski, G. H. and Sheidaei, F. and Skole, C. and Smith, A. W. and Staszak, D. and Telezhinsky, Igor O. and Tyler, J. and Varlotta, A. and Vincent, S. and Wakely, S. P. and Weekes, T. C. and Weinstein, A. and Welsing, R. and Zajczyk, A. and Zitzer, B.}, title = {Multiwavelemght oservatons of the TeV binary LS I+61 degrees 303 with veritas, fermi-lat, and swift/XRT during a TeV outburst}, series = {The astrophysical journal : an international review of spectroscopy and astronomical physics}, volume = {779}, journal = {The astrophysical journal : an international review of spectroscopy and astronomical physics}, number = {1}, publisher = {IOP Publ. Ltd.}, address = {Bristol}, issn = {0004-637X}, doi = {10.1088/0004-637X/779/1/88}, pages = {7}, year = {2013}, abstract = {We present the results of a multiwavelength observational campaign on the TeV binary system LS I +61 degrees 303 with the VERITAS telescope array (>200 GeV), Fermi-LAT (0.3-300 GeV), and Swift/XRT (2-10 keV). The data were taken from 2011 December through 2012 January and show a strong detection in all three wavebands. During this period VERITAS obtained 24.9 hr of quality selected livetime data in which LS I +61 degrees 303 was detected at a statistical significance of 11.9 sigma. These TeV observations show evidence for nightly variability in the TeV regime at a post-trial significance of 3.6 sigma. The combination of the simultaneously obtained TeV and X-ray fluxes do not demonstrate any evidence for a correlation between emission in the two bands. For the first time since the launch of the Fermi satellite in 2008, this TeV detection allows the construction of a detailed MeV-TeV spectral energy distribution from LS I +61 degrees 303. This spectrum shows a distinct cutoff in emission near 4 GeV, with emission seen by the VERITAS observations following a simple power-law above 200 GeV. This feature in the spectrum of LS I +61 degrees 303, obtained from overlapping observations with Fermi-LAT and VERITAS, may indicate that there are two distinct populations of accelerated particles producing the GeV and TeV emission.}, language = {en} } @article{ArchambaultBeilickeBenbowetal.2013, author = {Archambault, S. and Beilicke, M. and Benbow, W. and Berger, K. and Bird, R. and Bouvier, A. and Buckley, J. H. and Bugaev, V. and Byrum, K. and Cerruti, M. and Chen, Xuhui and Ciupik, L. and Connolly, M. P. and Cui, W. and Duke, C. and Dumm, J. and Errando, M. and Falcone, A. and Federici, Simone and Feng, Q. and Finley, J. P. and Fortson, L. and Furniss, A. and Galante, N. and Gillanders, G. H. and Griffin, S. and Griffiths, S. T. and Grube, J. and Gyuk, G. and Hanna, D. and Holder, J. and Hughes, G. and Humensky, T. B. and Kaaret, P. and Kertzman, M. and Khassen, Y. and Kieda, D. and Krawczynski, H. and Lang, M. J. and Madhavan, A. S. and Maier, G. and Majumdar, P. and McArthur, S. and McCann, A. and Moriarty, P. and Mukherjee, R. and Nieto, D. and de Bhroithe, A. O'Faolain and Ong, R. A. and Otte, A. N. and Pandel, D. and Park, N. and Perkins, J. S. and Pohl, Martin and Popkow, A. and Prokoph, H. and Quinn, J. and Ragan, K. and Rajotte, J. and Reyes, L. C. and Reynolds, P. T. and Richards, G. T. and Roache, E. and Sembroski, G. H. and Sheidaei, F. and Smith, A. W. and Staszak, D. and Telezhinsky, Igor O. and Theiling, M. and Tucci, J. V. and Tyler, J. and Varlotta, A. and Vincent, S. and Wakely, S. P. and Weekes, T. C. and Weinstein, A. and Williams, D. A. and Zitzer, B. and McCollough, M. L.}, title = {Veritas observatons of the microquasar cygnus X-3}, series = {The astrophysical journal : an international review of spectroscopy and astronomical physics}, volume = {779}, journal = {The astrophysical journal : an international review of spectroscopy and astronomical physics}, number = {2}, publisher = {IOP Publ. Ltd.}, address = {Bristol}, organization = {VERITAS Collaboration, Smithsonian Astrophys Observ}, issn = {0004-637X}, doi = {10.1088/0004-637X/779/2/150}, pages = {10}, year = {2013}, abstract = {We report results from TeV gamma-ray observations of the microquasar Cygnus X-3. The observations were made with the Very Energetic Radiation Imaging Telescope Array System (VERITAS) over a time period from 2007 June 11 to 2011 November 28. VERITAS is most sensitive to gamma rays at energies between 85 GeV and 30 TeV. The effective exposure time amounts to a total of about 44 hr, with the observations covering six distinct radio/X-ray states of the object. No significant TeV gamma-ray emission was detected in any of the states, nor with all observations combined. The lack of a positive signal, especially in the states where GeV gamma rays were detected, places constraints on TeV gamma-ray production in Cygnus X-3. We discuss the implications of the results.}, language = {en} } @article{tAliuArchambaultArlenetal.2013, author = {tAliu, E. and Archambault, S. and Arlen, T. and Aune, T. and Beilicke, M. and Benbow, W. and Bird, R. and Bouvier, A. and Bradbury, S. M. and Buckley, J. H. and Bugaev, V. and Byrum, K. and Cannon, A. and Cesarini, A. and Ciupik, L. and Collins-Hughes, E. and Connolly, M. P. and Cui, W. and Dickherber, R. and Duke, C. and Dumm, J. and Dwarkadas, Vikram V. and Errando, M. and Falcone, A. and Federici, Simone and Feng, Q. and Finley, J. P. and Finnegan, G. and Fortson, L. and Furniss, A. and Galante, N. and Gall, D. and Gillanders, G. H. and Godambe, S. and Gotthelf, E. V. and Griffin, S. and Grube, J. and Gyuk, G. and Hanna, D. and Holder, J. and Huan, H. and Hughes, G. and Humensky, T. B. and Kaaret, P. and Karlsson, N. and Kertzman, M. and Khassen, Y. and Kieda, D. and Krawczynski, H. and Krennrich, F. and Lang, M. J. and Lee, K. and Madhavan, A. S. and Maier, G. and Majumdar, P. and McArthur, S. and McCann, A. and Millis, J. and Moriarty, P. and Mukherjee, R. and Nelson, T. and de Bhroithe, A. O'Faolain and Ong, R. A. and Orr, M. and Otte, A. N. and Pandel, D. and Park, N. and Perkins, J. S. and Pohl, Martin and Popkow, A. and Prokoph, H. and Quinn, J. and Ragan, K. and Reyes, L. C. and Reynolds, P. T. and Roache, E. and Rose, H. J. and Ruppel, Jens and Saxon, D. B. and Schroedter, M. and Sembroski, G. H. and Sentuerk, G. D. and Skole, C. and Telezhinsky, Igor O. and Tesic, G. and Theiling, M. and Thibadeau, S. and Tsurusaki, K. and Tyler, J. and Varlotta, A. and Vassiliev, V. V. and Vincent, S. and Wakely, S. P. and Ward, J. E. and Weekes, T. C. and Weinstein, A. and Weisgarber, T. and Welsing, R. and Williams, D. A. and Zitzer, B.}, title = {Discovery of TeV Gamma-Ray emission toward supernova remnant SNR G78.2+2.1}, series = {The astrophysical journal : an international review of spectroscopy and astronomical physics}, volume = {770}, journal = {The astrophysical journal : an international review of spectroscopy and astronomical physics}, number = {2}, publisher = {IOP Publ. Ltd.}, address = {Bristol}, issn = {0004-637X}, doi = {10.1088/0004-637X/770/2/93}, pages = {7}, year = {2013}, abstract = {We report the discovery of an unidentified, extended source of very-high-energy gamma-ray emission, VER J2019+407, within the radio shell of the supernova remnant SNR G78.2+2.1, using 21.4 hr of data taken by the VERITAS gamma-ray observatory in 2009. These data confirm the preliminary indications of gamma-ray emission previously seen in a two-year (2007-2009) blind survey of the Cygnus region by VERITAS. VER J2019+407, which is detected at a post-trials significance of 7.5 standard deviations in the 2009 data, is localized to the northwestern rim of the remnant in a region of enhanced radio and X-ray emission. It has an intrinsic extent of 0 degrees.23 +/- 0 degrees.03(stat-0 degrees.02sys)(+0 degrees.04) and its spectrum is well-characterized by a differential power law (dN/dE = N-0 x (E/TeV)-Gamma) with a photon index of Gamma = 2.37 +/- 0.14(stat) +/- 0.20(sys) and a flux normalization of N-0 = 1.5 +/- 0.2(stat) +/- 0.4(sys) x 10(-12) photon TeV-1 cm(-2) s(-1). This yields an integral flux of 5.2 +/- 0.8(stat) +/- 1.4(sys) x 10(-12) photon cm(-2) s(-1) above 320 GeV, corresponding to 3.7\% of the Crab Nebula flux. We consider the relationship of the TeV gamma-ray emission with the GeV gamma-ray emission seen from SNR G78.2+2.1 as well as that seen from a nearby cocoon of freshly accelerated cosmic rays. Multiple scenarios are considered as possible origins for the TeV gamma-ray emission, including hadronic particle acceleration at the SNR shock.}, language = {en} } @article{RettigPohl2012, author = {Rettig, R. and Pohl, M.}, title = {The properties of non-thermal X-ray filaments in young supernova remnants}, series = {Astronomy and astrophysics : an international weekly journal}, volume = {545}, journal = {Astronomy and astrophysics : an international weekly journal}, number = {5}, publisher = {EDP Sciences}, address = {Les Ulis}, issn = {0004-6361}, doi = {10.1051/0004-6361/201219409}, pages = {9}, year = {2012}, abstract = {Context. Young supernova remnants (SNRs) exhibit narrow filaments of non-thermal X-ray emission whose widths can be limited either by electron energy losses or damping of the magnetic field. Aims. We want to investigate whether or not different models of these filaments can be observationally tested. Methods. Using observational parameters of four historical remnants, we calculated the filament profiles and compared the spectra of the filaments with those of the total non-thermal emission. For that purpose, we solved a one-dimensional stationary transport equation for the isotropic differential number density of the electrons. Results. We find that the difference between the spectra of filament and total non-thermal emission above 1 keV is more pronounced in the damping model than in the energy-loss model. Conclusions. A considerable damping of the magnetic field can result in an observable difference between the spectra of filament and total non-thermal emission, thus potentially permitting an observational discrimination between the energy-loss model and the damping model of the X-ray filaments.}, language = {en} } @article{NiemiecPohlBretetal.2012, author = {Niemiec, Jacek and Pohl, Martin and Bret, Antoine and Wieland, Volkmar}, title = {Nonrelativistic parallel shocks in unmagnetized and weakly magnetized plasmas}, series = {The astrophysical journal : an international review of spectroscopy and astronomical physics}, volume = {759}, journal = {The astrophysical journal : an international review of spectroscopy and astronomical physics}, number = {1}, publisher = {IOP Publ. Ltd.}, address = {Bristol}, issn = {0004-637X}, doi = {10.1088/0004-637X/759/1/73}, pages = {20}, year = {2012}, abstract = {We present results of 2D3V particle-in-cell simulations of nonrelativistic plasma collisions with absent or parallel large-scale magnetic field for parameters applicable to the conditions at young supernova remnants. We study the collision of plasma slabs of different density, leading to two different shocks and a contact discontinuity. Electron dynamics play an important role in the development of the system. While nonrelativistic shocks in both unmagnetized and magnetized plasmas can be mediated by Weibel-type instabilities, the efficiency of shock-formation processes is higher when a large-scale magnetic field is present. The electron distributions downstream of the forward and reverse shocks are generally isotropic, whereas that is not always the case for the ions. We do not see any significant evidence of pre-acceleration, neither in the electron population nor in the ion distribution.}, language = {en} } @article{AbdoAckermannAjelloetal.2011, author = {Abdo, A. A. and Ackermann, Margit and Ajello, M. and Allafort, A. J. and Baldini, L. and Ballet, J. and Barbiellini, G. and Baring, M. G. and Bastieri, D. and Bechtol, K. C. and Bellazzini, R. and Berenji, B. and Blandford, R. D. and Bloom, E. D. and Bonamente, E. and Borgland, A. W. and Bouvier, A. and Brandt, T. J. and Bregeon, Johan and Brez, A. and Brigida, M. and Bruel, P. and Buehler, R. and Buson, S. and Caliandro, G. A. and Cameron, R. A. and Cannon, A. and Caraveo, P. A. and Carrigan, Svenja and Casandjian, J. M. and Cavazzuti, E. and Cecchi, C. and Celik, O. and Charles, E. and Chekhtman, A. and Cheung, C. C. and Chiang, J. and Ciprini, S. and Claus, R. and Cohen-Tanugi, J. and Conrad, Jan and Cutini, S. and Dermer, C. D. and de Palma, F. and do Couto e Silva, E. and Drell, P. S. and Dubois, R. and Dumora, D. and Favuzzi, C. and Fegan, S. J. and Ferrara, E. C. and Focke, W. B. and Fortin, P. and Frailis, M. and Fuhrmann, L. and Fukazawa, Y. and Funk, S. and Fusco, P. and Gargano, F. and Gasparrini, D. and Gehrels, N. and Germani, S. and Giglietto, N. and Giordano, F. and Giroletti, M. and Glanzman, T. and Godfrey, G. and Grenier, I. A. and Guillemot, L. and Guiriec, S. and Hayashida, M. and Hays, E. and Horan, D. and Hughes, R. E. and Johannesson, G. and Johnson, A. S. and Johnson, W. N. and Kadler, M. and Kamae, T. and Katagiri, H. and Kataoka, J. and Knoedlseder, J. and Kuss, M. and Lande, J. and Latronico, L. and Lee, S. -H. and Lemoine-Goumard, M. and Longo, F. and Loparco, F. and Lott, B. and Lovellette, M. N. and Lubrano, P. and Madejski, G. M. and Makeev, A. and Max-Moerbeck, W. and Mazziotta, Mario Nicola and McEnery, J. E. and Mehault, J. and Michelson, P. F. and Mitthumsiri, W. and Mizuno, T. and Moiseev, A. A. and Monte, C. and Monzani, M. E. and Morselli, A. and Moskalenko, I. V. and Murgia, S. and Naumann-Godo, M. and Nishino, S. and Nolan, P. L. and Norris, J. P. and Nuss, E. and Ohsugi, T. and Okumura, A. and Omodei, N. and Orlando, E. and Ormes, J. F. and Paneque, D. and Panetta, J. H. and Parent, D. and Pavlidou, V. and Pearson, T. J. and Pelassa, V. and Pepe, M. and Pesce-Rollins, M. and Piron, F. and Porter, T. A. and Raino, S. and Rando, R. and Razzano, M. and Readhead, A. and Reimer, A. and Reimer, O. and Richards, J. L. and Ripken, J. and Ritz, S. and Roth, M. and Sadrozinski, H. F. -W. and Sanchez, D. and Sander, A. and Scargle, J. D. and Sgro, C. and Siskind, E. J. and Smith, P. D. and Spandre, G. and Spinelli, P. and Stawarz, L. and Stevenson, M. and Strickman, M. S. and Sokolovsky, K. V. and Suson, D. J. and Takahashi, H. and Takahashi, T. and Tanaka, T. and Thayer, J. B. and Thayer, J. G. and Thompson, D. J. and Tibaldo, L. and Torres, F. and Tosti, G. and Tramacere, A. and Uchiyama, Y. and Usher, T. L. and Vandenbroucke, J. and Vasileiou, V. and Vilchez, N. and Vitale, V. and Waite, A. P. and Wang, P. and Wehrle, A. E. and Winer, B. L. and Wood, K. S. and Yang, Z. and Ylinen, T. and Zensus, J. A. and Ziegler, M. and Aleksic, J. and Antonelli, L. A. and Antoranz, P. and Backes, Michael and Barrio, J. A. and Gonzalez, J. Becerra and Bednarek, W. and Berdyugin, A. and Berger, K. and Bernardini, E. and Biland, A. and Blanch Bigas, O. and Bock, R. K. and Boller, A. and Bonnoli, G. and Bordas, Pol and Tridon, D. Borla and Bosch-Ramon, Valentin and Bose, D. and Braun, I. and Bretz, T. and Camara, M. and Carmona, E. and Carosi, A. and Colin, P. and Colombo, E. and Contreras, J. L. and Cortina, J. and Covino, S. and Dazzi, F. and de Angelis, A. and del Pozo, E. De Cea and De Lotto, B. and De Maria, M. and De Sabata, F. and Mendez, C. Delgado and Ortega, A. Diago and Doert, M. and Dominguez, A. and Prester, Dijana Dominis and Dorner, D. and Doro, M. and Elsaesser, D. and Ferenc, D. and Fonseca, M. V. and Font, L. and Lopen, R. J. Garcia and Garczarczyk, M. and Gaug, M. and Giavitto, G. and Godinovi, N. and Hadasch, D. and Herrero, A. and Hildebrand, D. and Hoehne-Moench, D. and Hose, J. and Hrupec, D. and Jogler, T. and Klepser, S. and Kraehenbuehl, T. and Kranich, D. and Krause, J. and La Barbera, A. and Leonardo, E. and Lindfors, E. and Lombardi, S. and Lopez, M. and Lorenz, E. and Majumdar, P. and Makariev, E. and Maneva, G. and Mankuzhiyil, N. and Mannheim, K. and Maraschi, L. and Mariotti, M. and Martinez, M. and Mazin, D. and Meucci, M. and Miranda, J. M. and Mirzoyan, R. and Miyamoto, H. and Moldon, J. and Moralejo, A. and Nieto, D. and Nilsson, K. and Orito, R. and Oya, I. and Paoletti, R. and Paredes, J. M. and Partini, S. and Pasanen, M. and Pauss, F. and Pegna, R. G. and Perez-Torres, M. A. and Persic, M. and Peruzzo, J. and Pochon, J. and Moroni, P. G. Prada and Prada, F. and Prandini, E. and Puchades, N. and Puljak, I. and Reichardt, T. and Reinthal, R. and Rhode, W. and Ribo, M. and Rico, J. and Rissi, M. and Ruegamer, S. and Saggion, A. and Saito, K. and Saito, T. Y. and Salvati, M. and Sanchez-Conde, M. and Satalecka, K. and Scalzotto, V. and Scapin, V. and Schultz, C. and Schweizer, T. and Shayduk, M. and Shore, S. N. and Sierpowska-Bartosik, A. and Sillanpaa, A. and Sitarek, J. and Sobczynska, D. and Spanier, F. and Spiro, S. and Stamerra, A. and Steinke, B. and Storz, J. and Strah, N. and Struebig, J. C. and Suric, T. and Takalo, L. O. and Tavecchio, F. and Temnikov, P. and Terzic, T. and Tescaro, D. and Teshima, M. and Vankov, H. and Wagner, R. M. and Weitzel, Q. and Zabalza, V. and Zandanel, F. and Zanin, R. and Acciari, V. A. and Arlen, T. and Aune, T. and Benbow, W. and Boltuch, D. and Bradbury, S. M. and Buckley, J. H. and Bugaev, V. and Cannon, A. and Cesarini, A. and Ciupik, L. and Cui, W. and Dickherber, R. and Errando, M. and Falcone, A. and Finley, J. P. and Finnegan, G. and Fortson, L. and Furniss, A. and Galante, N. and Gall, D. and Gillanders, G. H. and Godambe, S. and Grube, J. and Guenette, R. and Gyuk, G. and Hanna, D. and Holder, J. and Huang, D. and Hui, C. M. and Humensky, T. B. and Kaaret, P. and Karlsson, N. and Kertzman, M. and Kieda, D. and Konopelko, A. and Krawczynski, H. and Krennrich, F. and Lang, M. J. and Maier, G. and McArthur, S. and McCann, A. and McCutcheon, M. and Moriarty, P. and Mukherjee, R. and Ong, R. and Otte, N. and Pandel, D. and Perkins, J. S. and Pichel, A. and Pohl, M. and Quinn, J. and Ragan, K. and Reyes, L. C. and Reynolds, P. T. and Roache, E. and Rose, H. J. and Rovero, A. C. and Schroedter, M. and Sembroski, G. H. and Senturk, G. D. and Steele, D. and Swordy, S. P. and Tesic, G. and Theiling, M. and Thibadeau, S. and Varlotta, A. and Vincent, S. and Wakely, S. P. and Ward, J. E. and Weekes, T. C. and Weinstein, A. and Weisgarber, T. and Williams, D. A. and Wood, M. and Zitzer, B. and Villata, M. and Raiteri, C. M. and Aller, H. D. and Aller, M. F. and Arkharov, A. A. and Blinov, D. A. and Calcidese, P. and Chen, W. P. and Efimova, N. V. and Kimeridze, G. and Konstantinova, T. S. and Kopatskaya, E. N. and Koptelova, E. and Kurtanidze, O. M. and Kurtanidze, S. O. and Lahteenmaki, A. and Larionov, V. M. and Larionova, E. G. and Larionova, L. V. and Ligustri, R. and Morozova, D. A. and Nikolashvili, M. G. and Sigua, L. A. and Troitsky, I. S. and Angelakis, E. and Capalbi, M. and Carraminana, A. and Carrasco, L. and Cassaro, P. and de la Fuente, E. and Gurwell, M. A. and Kovalev, Y. Y. and Kovalev, Yu. A. and Krichbaum, T. P. and Krimm, H. A. and Leto, Paolo and Lister, M. L. and Maccaferri, G. and Moody, J. W. and Mori, Y. and Nestoras, I. and Orlati, A. and Pagani, C. and Pace, C. and Pearson, R. and Perri, M. and Piner, B. G. and Pushkarev, A. B. and Ros, E. and Sadun, A. C. and Sakamoto, T. and Tornikoski, M. and Yatsu, Y. and Zook, A.}, title = {Insights into the high-energy gamma-Ray emission of markarian 501 fromextensive multifrequency observations in the fermi era}, series = {The astrophysical journal : an international review of spectroscopy and astronomical physics}, volume = {727}, journal = {The astrophysical journal : an international review of spectroscopy and astronomical physics}, number = {2}, publisher = {IOP Publ. Ltd.}, address = {Bristol}, organization = {Fermi-LAT Collaboration, MAGIC Collaboration, VERITAS Collaboration}, issn = {0004-637X}, doi = {10.1088/0004-637X/727/2/129}, pages = {26}, year = {2011}, abstract = {We report on the gamma-ray activity of the blazar Mrk 501 during the first 480 days of Fermi operation. We find that the average Large Area Telescope (LAT) gamma-ray spectrum of Mrk 501 can be well described by a single power-law function with a photon index of 1.78 +/- 0.03. While we observe relatively mild flux variations with the Fermi-LAT (within less than a factor of two), we detect remarkable spectral variability where the hardest observed spectral index within the LAT energy range is 1.52 +/- 0.14, and the softest one is 2.51 +/- 0.20. These unexpected spectral changes do not correlate with the measured flux variations above 0.3 GeV. In this paper, we also present the first results from the 4.5 month long multifrequency campaign (2009 March 15-August 1) on Mrk 501, which included the Very Long Baseline Array (VLBA), Swift, RXTE, MAGIC, and VERITAS, the F-GAMMA, GASP-WEBT, and other collaborations and instruments which provided excellent temporal and energy coverage of the source throughout the entire campaign. The extensive radio to TeV data set from this campaign provides us with the most detailed spectral energy distribution yet collected for this source during its relatively low activity. The average spectral energy distribution of Mrk 501 is well described by the standard one-zone synchrotron self-Compton (SSC) model. In the framework of this model, we find that the dominant emission region is characterized by a size less than or similar to 0.1 pc (comparable within a factor of few to the size of the partially resolved VLBA core at 15-43 GHz), and that the total jet power (similar or equal to 10(44) erg s(-1)) constitutes only a small fraction (similar to 10(-3)) of the Eddington luminosity. The energy distribution of the freshly accelerated radiating electrons required to fit the time-averaged data has a broken power-law form in the energy range 0.3 GeV-10 TeV, with spectral indices 2.2 and 2.7 below and above the break energy of 20 GeV. We argue that such a form is consistent with a scenario in which the bulk of the energy dissipation within the dominant emission zone of Mrk 501 is due to relativistic, proton-mediated shocks. We find that the ultrarelativistic electrons and mildly relativistic protons within the blazar zone, if comparable in number, are in approximate energy equipartition, with their energy dominating the jet magnetic field energy by about two orders of magnitude.}, language = {en} } @article{AbdoAckermannAjelloetal.2011, author = {Abdo, A. A. and Ackermann, Margit and Ajello, M. and Allafort, A. J. and Baldini, L. and Ballet, J. and Barbiellini, G. and Baring, M. G. and Bastieri, D. and Bellazzini, R. and Berenji, B. and Blandford, R. D. and Bloom, E. D. and Bonamente, E. and Borgland, A. W. and Bouvier, A. and Brandt, T. J. and Bregeon, Johan and Brigida, M. and Bruel, P. and Buehler, R. and Buson, S. and Caliandro, G. A. and Cameron, R. A. and Caraveo, P. A. and Casandjian, J. M. and Cecchi, C. and Chaty, S. and Chekhtman, A. and Cheung, C. C. and Chiang, J. and Cillis, A. N. and Ciprini, S. and Claus, R. and Cohen-Tanugi, J. and Conrad, Jan and Corbel, S. and Cutini, S. and de Angelis, A. and de Palma, F. and Dermer, C. D. and Digel, S. W. and do Couto e Silva, E. and Drell, P. S. and Drlica-Wagner, A. and Dubois, R. and Dumora, D. and Favuzzi, C. and Ferrara, E. C. and Fortin, P. and Frailis, M. and Fukazawa, Y. and Fukui, Y. and Funk, S. and Fusco, P. and Gargano, F. and Gasparrini, D. and Gehrels, N. and Germani, S. and Giglietto, N. and Giordano, F. and Giroletti, M. and Glanzman, T. and Godfrey, G. and Grenier, I. A. and Grondin, M. -H. and Guiriec, S. and Hadasch, D. and Hanabata, Y. and Harding, A. K. and Hayashida, M. and Hayashi, K. and Hays, E. and Horan, D. and Jackson, M. S. and Johannesson, G. and Johnson, A. S. and Kamae, T. and Katagiri, H. and Kataoka, J. and Kerr, M. and Knoedlseder, J. and Kuss, M. and Lande, J. and Latronico, L. and Lee, S. -H. and Lemoine-Goumard, M. and Longo, F. and Loparco, F. and Lovellette, M. N. and Lubrano, P. and Madejski, G. M. and Makeev, A. and Mazziotta, Mario Nicola and McEnery, J. E. and Michelson, P. F. and Mignani, R. P. and Mitthumsiri, W. and Mizuno, T. and Moiseev, A. A. and Monte, C. and Monzani, M. E. and Morselli, A. and Moskalenko, I. V. and Murgia, S. and Naumann-Godo, M. and Nolan, P. L. and Norris, J. P. and Nuss, E. and Ohsugi, T. and Okumura, A. and Orlando, E. and Ormes, J. F. and Paneque, D. and Parent, D. and Pelassa, V. and Pesce-Rollins, M. and Pierbattista, M. and Piron, F. and Pohl, Martin and Porter, T. A. and Raino, S. and Rando, R. and Razzano, M. and Reimer, O. and Reposeur, T. and Ritz, S. and Romani, R. W. and Roth, M. and Sadrozinski, H. F. -W. and Parkinson, P. M. Saz and Sgro, C. and Smith, D. A. and Smith, P. D. and Spandre, G. and Spinelli, P. and Strickman, M. S. and Tajima, H. and Takahashi, H. and Takahashi, T. and Tanaka, T. and Thayer, J. G. and Thayer, J. B. and Thompson, D. J. and Tibaldo, L. and Tibolla, O. and Torres, D. F. and Tosti, G. and Tramacere, A. and Troja, E. and Uchiyama, Y. and Vandenbroucke, J. and Vasileiou, V. and Vianello, G. and Vilchez, N. and Vitale, V. and Waite, A. P. and Wang, P. and Winer, B. L. and Wood, K. S. and Yamamoto, H. and Yamazaki, R. and Yang, Z. and Ziegler, M.}, title = {Observations of the young supernova remnant RX J1713.7-3946 with the fermi large area telescope}, series = {The astrophysical journal : an international review of spectroscopy and astronomical physics}, volume = {734}, journal = {The astrophysical journal : an international review of spectroscopy and astronomical physics}, number = {1}, publisher = {IOP Publ. Ltd.}, address = {Bristol}, issn = {0004-637X}, doi = {10.1088/0004-637X/734/1/28}, pages = {9}, year = {2011}, abstract = {We present observations of the young supernova remnant (SNR) RX J1713.7-3946 with the Fermi Large Area Telescope (LAT). We clearly detect a source positionally coincident with the SNR. The source is extended with a best-fit extension of 0 degrees.55 +/- 0 degrees.04 matching the size of the non-thermal X-ray and TeV gamma-ray emission from the remnant. The positional coincidence and the matching extended emission allow us to identify the LAT source with SNR RX J1713.7-3946. The spectrum of the source can be described by a very hard power law with a photon index of Gamma = 1.5 +/- 0.1 that coincides in normalization with the steeper H. E. S. S.-detected gamma-ray spectrum at higher energies. The broadband gamma-ray emission is consistent with a leptonic origin as the dominant mechanism for the gamma-ray emission.}, language = {en} } @article{AcciariAliuArayaetal.2011, author = {Acciari, V. A. and Aliu, E. and Araya, M. and Arlen, T. and Aune, T. and Beilicke, M. and Benbow, W. and Bradbury, S. M. and Buckley, J. H. and Bugaev, V. and Byrum, K. and Cannon, A. and Cesarini, A. and Ciupik, L. and Collins-Hughes, E. and Cui, W. and Dickherber, R. and Duke, C. and Falcone, A. and Finley, J. P. and Fortson, L. and Furniss, A. and Galante, N. and Gall, D. and Godambe, S. and Griffin, S. and Guenette, R. and Gyuk, G. and Hanna, D. and Holder, J. and Hughes, G. and Hui, C. M. and Humensky, T. B. and Imran, A. and Kaaret, P. and Kertzman, M. and Krawczynski, H. and Krennrich, F. and Madhavan, A. S. and Maier, G. and Majumdar, P. and McArthur, S. and Moriarty, P. and Ong, R. A. and Otte, A. N. and Pandel, D. and Park, N. and Perkins, J. S. and Pohl, Martin and Prokoph, H. and Quinn, J. and Ragan, K. and Reyes, L. C. and Reynolds, P. T. and Roache, E. and Rose, H. J. and Saxon, D. B. and Sembroski, G. H. and Sentuerk, G. D. and Smith, A. W. and Tesic, G. and Theiling, M. and Thibadeau, S. and Varlotta, A. and Vincent, S. and Vivier, M. and Wakely, S. P. and Ward, J. E. and Weekes, T. C. and Weinstein, A. and Weisgarber, T. and Weng, S. and Williams, D. A. and Wood, M. and Zitzer, B.}, title = {Gamma-ray observations of the Be/Pulsar binary 1A 0535+262 during a Giant X-Ray outburst}, series = {The astrophysical journal : an international review of spectroscopy and astronomical physics}, volume = {733}, journal = {The astrophysical journal : an international review of spectroscopy and astronomical physics}, number = {2}, publisher = {IOP Publ. Ltd.}, address = {Bristol}, issn = {0004-637X}, doi = {10.1088/0004-637X/733/2/96}, pages = {10}, year = {2011}, abstract = {Giant X-ray outbursts, with luminosities of about 10(37) erg s(-1), are observed roughly every five years from the nearby Be/pulsar binary 1A 0535+262. In this article, we present observations of the source with VERITAS at very high energies (VHEs; E > 100 GeV) triggered by the X-ray outburst in 2009 December. The observations started shortly after the onset of the outburst and provided comprehensive coverage of the episode, as well as the 111 day binary orbit. No VHE emission is evident at any time. We also examined data from the contemporaneous observations of 1A 0535+262 with the Fermi/Large Area Telescope at high-energy photons (E > 0.1 GeV) and failed to detect the source at GeV energies. The X-ray continua measured with the Swift/X-Ray Telescope and the RXTE/PCA can be well described by the combination of blackbody and Comptonized emission from thermal electrons. Therefore, the gamma-ray and X-ray observations suggest the absence of a significant population of non-thermal particles in the system. This distinguishes 1A 0535+262 from those Be X-ray binaries (such as PSR B1259-63 and LS I +61 degrees 303) that have been detected at GeV-TeV energies. We discuss the implications of the results on theoretical models.}, language = {en} }