TY - JOUR
A1 - Aliu, E.
A1 - Aune, T.
A1 - Barnacka, A.
A1 - Beilicke, M.
A1 - Benbow, W.
A1 - Berger, K.
A1 - Biteau, J.
A1 - Buckley, J. H.
A1 - Bugaev, V.
A1 - Byrum, K.
A1 - Cardenzana, J. V.
A1 - Cerruti, M.
A1 - Chen, Xuhui
A1 - Ciupik, L.
A1 - Connaughton, V.
A1 - Cui, W.
A1 - Dickinson, H. J.
A1 - Eisch, J. D.
A1 - Errando, M.
A1 - Falcone, A.
A1 - Federici, Simone
A1 - Feng, Q.
A1 - Finley, J. P.
A1 - Fleischhack, H.
A1 - Fortin, P.
A1 - Fortson, L.
A1 - Furniss, A.
A1 - Galante, N.
A1 - Gillanders, G. H.
A1 - Griffin, S.
A1 - Griffiths, S. T.
A1 - Grube, J.
A1 - Gyuk, G.
A1 - Hakansson, Nils
A1 - Hanna, D.
A1 - Holder, J.
A1 - Hughes, G.
A1 - Humensky, T. B.
A1 - Johnson, C. A.
A1 - Kaaret, P.
A1 - Kar, P.
A1 - Kertzman, M.
A1 - Khassen, Y.
A1 - Kieda, D.
A1 - Krawczynski, H.
A1 - Krennrich, F.
A1 - Lang, M. J.
A1 - Madhavan, A. S.
A1 - Maier, G.
A1 - McArthur, S.
A1 - McCann, A.
A1 - Meagher, K.
A1 - Millis, J.
A1 - Moriarty, P.
A1 - Mukherjee, R.
A1 - Nieto, D.
A1 - Ong, R. A.
A1 - Otte, A. N.
A1 - Park, N.
A1 - Pohl, Martin
A1 - Popkow, A.
A1 - Prokoph, H.
A1 - Pueschel, E.
A1 - Quinn, J.
A1 - Ragan, K.
A1 - Rajotte, J.
A1 - Reyes, L. C.
A1 - Reynolds, P. T.
A1 - Richards, G. T.
A1 - Roache, E.
A1 - Sembroski, G. H.
A1 - Shahinyan, K.
A1 - Smith, A. W.
A1 - Staszak, D.
A1 - Telezhinsky, Igor
A1 - Tucci, J. V.
A1 - Tyler, J.
A1 - Varlotta, A.
A1 - Vassiliev, V. V.
A1 - Vincent, S.
A1 - Wakely, S. P.
A1 - Weiner, O. M.
A1 - Weinstein, A.
A1 - Welsing, R.
A1 - Wilhelm, Alina
A1 - Williams, D. A.
A1 - Zitzer, B.
A1 - McEnery, J. E.
A1 - Perkins, J. S.
A1 - Veres, P.
A1 - Zhu, S.
T1 - Constraints on very high energy emission from GRB 130427A
JF - The astrophysical journal : an international review of spectroscopy and astronomical physics ; Part 2, Letters
N2 - Prompt emission from the very fluent and nearby (z = 0.34) gamma-ray burst GRB130427A was detected by several orbiting telescopes and by ground-based, wide-field-of-view optical transient monitors. Apart from the intensity and proximity of this GRB, it is exceptional due to the extremely long-lived high-energy (100 MeV to 100 GeV) gamma-ray emission, which was detected by the Large Area Telescope on the Fermi Gamma-Ray Space Telescope for similar to 70 ks after the initial burst. The persistent, hard-spectrum, high-energy emission suggests that the highest-energy gamma rays may have been produced via synchrotron self-Compton processes though there is also evidence that the high-energy emission may instead be an extension of the synchrotron spectrum. VERITAS, a ground-based imaging atmospheric Cherenkov telescope array, began follow-up observations of GRB130427A similar to 71 ks (similar to 20 hr) after the onset of the burst. The GRB was not detected with VERITAS; however, the high elevation of the observations, coupled with the low redshift of the GRB, make VERITAS a very sensitive probe of the emission from GRB130427A for E > 100 GeV. The non-detection and consequent upper limit derived place constraints on the synchrotron self-Compton model of high-energy gamma-ray emission from this burst.
KW - gamma-ray burst: individual (GRB 130427A)
Y1 - 2014
U6 - http://dx.doi.org/10.1088/2041-8205/795/1/L3
SN - 2041-8205 (print)
SN - 2041-8213 (online)
VL - 795
IS - 1
PB - IOP Publ. Ltd.
CY - Bristol
ER -
TY - JOUR
A1 - Archer, A.
A1 - Barnacka, A.
A1 - Beilicke, M.
A1 - Benbow, W.
A1 - Berger, K.
A1 - Bird, R.
A1 - Biteau, J.
A1 - Buckley, J. H.
A1 - Bugaev, V.
A1 - Byrum, K.
A1 - Cardenzana, J. V.
A1 - Cerruti, M.
A1 - Chen, W.
A1 - Chen, Xiaoming
A1 - Ciupik, L.
A1 - Connolly, M. P.
A1 - Cui, W.
A1 - Dickinson, H. J.
A1 - Dumm, J.
A1 - Eisch, J. D.
A1 - Falcone, A.
A1 - Federici, Simone
A1 - Feng, Q.
A1 - Finley, J. P.
A1 - Fleischhack, H.
A1 - Fortson, L.
A1 - Furniss, A.
A1 - Galante, N.
A1 - Griffin, S.
A1 - Griffiths, S. T.
A1 - Grube, J.
A1 - Gyuk, G.
A1 - Hakansson, Nils
A1 - Hanna, D.
A1 - Holder, J.
A1 - Hughes, G.
A1 - Johnson, C. A.
A1 - Kaaret, P.
A1 - Kar, P.
A1 - Kertzman, M.
A1 - Khassen, Y.
A1 - Kieda, D.
A1 - Krawczynski, H.
A1 - Kumar, S.
A1 - Lang, M. J.
A1 - Maier, G.
A1 - McArthur, S.
A1 - McCann, A.
A1 - Meagher, K.
A1 - Moriarty, P.
A1 - Mukherjee, R.
A1 - Nieto, D.
A1 - Ong, R. A.
A1 - Otte, A. N.
A1 - Park, N.
A1 - Perkins, J. S.
A1 - Pohl, Manuela
A1 - Popkow, A.
A1 - Prokoph, H.
A1 - Pueschel, E.
A1 - Quinn, J.
A1 - Ragan, K.
A1 - Rajotte, J.
A1 - Reyes, L. C.
A1 - Reynolds, P. T.
A1 - Richards, G. T.
A1 - Roache, E.
A1 - Sembroski, G. H.
A1 - Shahinyan, K.
A1 - Smith, A. W.
A1 - Staszak, D.
A1 - Telezhinsky, Igor
A1 - Tucci, J. V.
A1 - Tyler, J.
A1 - Varlotta, A.
A1 - Vincent, S.
A1 - Wakely, S. P.
A1 - Weinstein, A.
A1 - Welsing, R.
A1 - Wilhelm, A.
A1 - Williams, D. A.
A1 - Zajczyk, A.
A1 - Zitzer, B.
T1 - Very-high energy observations of the galactic center region by veritas IN 2010-2012
JF - The astrophysical journal : an international review of spectroscopy and astronomical physics
N2 - The Galactic center is an interesting region for high-energy (0.1-100 GeV) and very-high-energy (E > 100 GeV) gamma-ray observations. Potential sources of GeV/TeV gamma-ray emission have been suggested, e.g., the accretion of matter onto the supermassive black hole, cosmic rays from a nearby supernova remnant (e.g., Sgr A East), particle acceleration in a plerion, or the annihilation of dark matter particles. The Galactic center has been detected by EGRET and by Fermi/LAT in the MeV/GeV energy band. At TeV energies, the Galactic center was detected with moderate significance by the CANGAROO and Whipple 10 m telescopes and with high significance by H.E.S.S., MAGIC, and VERITAS. We present the results from three years of VERITAS observations conducted at large zenith angles resulting in a detection of the Galactic center on the level of 18 standard deviations at energies above similar to 2.5 TeV. The energy spectrum is derived and is found to be compatible with hadronic, leptonic, and hybrid emission models discussed in the literature. Future, more detailed measurements of the high-energy cutoff and better constraints on the high-energy flux variability will help to refine and/or disentangle the individual models.
KW - astroparticle physics
KW - black hole physics
KW - Galaxy: center
KW - gamma rays: galaxies
KW - methods: data analysis
KW - radiation mechanisms: non-thermal
Y1 - 2014
U6 - http://dx.doi.org/10.1088/0004-637X/790/2/149
SN - 0004-637X (print)
SN - 1538-4357 (online)
VL - 790
IS - 2
PB - IOP Publ. Ltd.
CY - Bristol
ER -
TY - JOUR
A1 - Aleksic, J.
A1 - Ansoldi, S.
A1 - Antonelli, L. A.
A1 - Antoranz, P.
A1 - Babic, A.
A1 - Bangale, P.
A1 - de Almeida, U. Barres
A1 - Barrio, J. A.
A1 - Gonzalez, J. Becerra
A1 - Bednarek, W.
A1 - Bernardini, E.
A1 - Biasuzzi, B.
A1 - Biland, A.
A1 - Blanch, O.
A1 - Boller, A.
A1 - Bonnefoy, S.
A1 - Bonnoli, G.
A1 - Borracci, F.
A1 - Bretz, T.
A1 - Carmona, E.
A1 - Carosi, A.
A1 - Colin, P.
A1 - Colombo, E.
A1 - Contreras, J. L.
A1 - Cortina, J.
A1 - Covino, S.
A1 - Da Vela, P.
A1 - Dazzi, F.
A1 - De Angelis, A.
A1 - De Caneva, G.
A1 - De Lotto, B.
A1 - Wilhelmi, E. de Ona
A1 - Mendez, C. Delgado
A1 - Prester, Dijana Dominis
A1 - Dorner, D.
A1 - Doro, M.
A1 - Einecke, S.
A1 - Eisenacher, D.
A1 - Elsaesser, D.
A1 - Fonseca, M. V.
A1 - Font, L.
A1 - Frantzen, K.
A1 - Fruck, C.
A1 - Galindo, D.
A1 - Lopez, R. J. Garcia
A1 - Garczarczyk, M.
A1 - Terrats, D. Garrido
A1 - Gaug, M.
A1 - Godinovic, N.
A1 - Munoz, A. Gonzalez
A1 - Gozzini, S. R.
A1 - Hadasch, D.
A1 - Hanabata, Y.
A1 - Hayashida, M.
A1 - Herrera, J.
A1 - Hildebrand, D.
A1 - Hose, J.
A1 - Hrupec, D.
A1 - Hughes, G.
A1 - Idec, W.
A1 - Kadenius, V.
A1 - Kellermann, H.
A1 - Knoetig, M. L.
A1 - Kodani, K.
A1 - Konno, Y.
A1 - Krause, J.
A1 - Kubo, H.
A1 - Kushida, J.
A1 - La Barbera, A.
A1 - Lelas, D.
A1 - Lewandowska, N.
A1 - Lindfors, E.
A1 - Lombardi, S.
A1 - Lopez, M.
A1 - Lopez-Coto, R.
A1 - Lopez-Oramas, A.
A1 - Lorenz, E.
A1 - Lozano, I.
A1 - Makariev, M.
A1 - Mallot, K.
A1 - Maneva, G.
A1 - Mankuzhiyil, N.
A1 - Mannheim, K.
A1 - Maraschi, L.
A1 - Marcote, B.
A1 - Mariotti, M.
A1 - Martinez, M.
A1 - Mazin, D.
A1 - Menzel, U.
A1 - Miranda, J. M.
A1 - Mirzoyan, R.
A1 - Moralejo, A.
A1 - Munar-Adrover, P.
A1 - Nakajima, D.
A1 - Niedzwiecki, A.
A1 - Nilsson, K.
A1 - Nishijima, K.
A1 - Noda, K.
A1 - Orito, R.
A1 - Overkemping, A.
A1 - Paiano, S.
A1 - Palatiello, M.
A1 - Paneque, D.
A1 - Paoletti, R.
A1 - Paredes, J. M.
A1 - Paredes-Fortuny, X.
A1 - Persic, M.
A1 - Moroni, P. G. Prada
A1 - Prandini, E.
A1 - Puljak, I.
A1 - Reinthal, R.
A1 - Rhode, W.
A1 - Ribo, M.
A1 - Rico, J.
A1 - Garcia, J. Rodriguez
A1 - Rugamer, S.
A1 - Saito, T.
A1 - Saito, K.
A1 - Satalecka, K.
A1 - Scalzotto, V.
A1 - Scapin, V.
A1 - Schultz, C.
A1 - Schweizer, T.
A1 - Sun, S.
A1 - Shore, S. N.
A1 - Sillanpaa, A.
A1 - Sitarek, J.
A1 - Snidaric, I.
A1 - Sobczynska, D.
A1 - Spanier, F.
A1 - Stamatescu, V.
A1 - Stamerra, A.
A1 - Steinbring, T.
A1 - Steinke, B.
A1 - Storz, J.
A1 - Strzys, M.
A1 - Takalo, L.
A1 - Takami, H.
A1 - Tavecchio, F.
A1 - Temnikov, P.
A1 - Terzic, T.
A1 - Tescaro, D.
A1 - Teshima, M.
A1 - Thaele, J.
A1 - Tibolla, O.
A1 - Torres, D. F.
A1 - Toyama, T.
A1 - Treves, A.
A1 - Uellenbeck, M.
A1 - Vogler, P.
A1 - Zanin, R.
A1 - Archambault, S.
A1 - Archer, A.
A1 - Beilicke, M.
A1 - Benbow, W.
A1 - Berger, K.
A1 - Bird, R.
A1 - Biteau, J.
A1 - Buckley, J. H.
A1 - Bugaev, V.
A1 - Cerruti, M.
A1 - Chen, Xiaoming
A1 - Ciupik, L.
A1 - Collins-Hughes, E.
A1 - Cui, W.
A1 - Eisch, J. D.
A1 - Falcone, A.
A1 - Feng, Q.
A1 - Finley, J. P.
A1 - Fortin, P.
A1 - Fortson, L.
A1 - Furniss, A.
A1 - Galante, N.
A1 - Gillanders, G. H.
A1 - Griffin, S.
A1 - Gyuk, G.
A1 - Hakansson, Nils
A1 - Holder, J.
A1 - Johnson, C. A.
A1 - Kaaret, P.
A1 - Kar, P.
A1 - Kertzman, M.
A1 - Kieda, D.
A1 - Lang, M. J.
A1 - McArthur, S.
A1 - McCann, A.
A1 - Meagher, K.
A1 - Millis, J.
A1 - Moriarty, P.
A1 - Ong, R. A.
A1 - Otte, A. N.
A1 - Perkins, J. S.
A1 - Pichel, A.
A1 - Pohl, Manuela
A1 - Popkow, A.
A1 - Prokoph, H.
A1 - Pueschel, E.
A1 - Ragan, K.
A1 - Reyes, L. C.
A1 - Reynolds, P. T.
A1 - Richards, G. T.
A1 - Roache, E.
A1 - Rovero, A. C.
A1 - Sembroski, G. H.
A1 - Shahinyan, K.
A1 - Staszak, D.
A1 - Telezhinsky, Igor
A1 - Tucci, J. V.
A1 - Tyler, J.
A1 - Varlotta, A.
A1 - Wakely, S. P.
A1 - Welsing, R.
A1 - Wilhelm, Alina
A1 - Williams, D. A.
A1 - Buson, S.
A1 - Finke, J.
A1 - Villata, M.
A1 - Raiteri, C.
A1 - Aller, H. D.
A1 - Aller, M. F.
A1 - Cesarini, A.
A1 - Chen, W. P.
A1 - Gurwell, M. A.
A1 - Jorstad, S. G.
A1 - Kimeridze, G. N.
A1 - Koptelova, E.
A1 - Kurtanidze, O. M.
A1 - Kurtanidze, S. O.
A1 - Lahteenmaki, A.
A1 - Larionov, V. M.
A1 - Larionova, E. G.
A1 - Lin, H. C.
A1 - McBreen, B.
A1 - Moody, J. W.
A1 - Morozova, D. A.
A1 - Marscher, A. P.
A1 - Max-Moerbeck, W.
A1 - Nikolashvili, M. G.
A1 - Perri, M.
A1 - Readhead, A. C. S.
A1 - Richards, J. L.
A1 - Ros, J. A.
A1 - Sadun, A. C.
A1 - Sakamoto, T.
A1 - Sigua, L. A.
A1 - Smith, P. S.
A1 - Tornikoski, M.
A1 - Troitsky, I. S.
A1 - Wehrle, A. E.
A1 - Jordan, B.
T1 - Unprecedented study of the broadband emission of Mrk 421 during flaring activity in March 2010
JF - Astronomy and astrophysics : an international weekly journal
N2 - Context. Because of its proximity, Mrk 421 is one of the best sources on which to study the nature of BL Lac objects. Its proximity allows us to characterize its broadband spectral energy distribution (SED).
Aims. The goal is to better understand the mechanisms responsible for the broadband emission and the temporal evolution of Mrk 421. These mechanisms may also apply to more distant blazars that cannot be studied with the same level of detail.
Methods. A flare occurring in March 2010 was observed for 13 consecutive days (from MJD 55 265 to MJD 55 277) with unprecedented wavelength coverage from radio to very high energy (VHE; E > 100 GeV) gamma-rays with MAGIC, VERITAS, Whipple, Fermi-LAT, MAXI, RXTE, Swift, GASP-WEBT, and several optical and radio telescopes. We modeled the day-scale SEDs with one-zone and two-zone synchrotron self-Compton (SSC) models, investigated the physical parameters, and evaluated whether the observed broadband SED variability can be associated with variations in the relativistic particle population.
Results. The activity of Mrk 421 initially was high and then slowly decreased during the 13-day period. The flux variability was remarkable at the X-ray and VHE bands, but it was minor or not significant at the other bands. The variability in optical polarization was also minor. These observations revealed an almost linear correlation between the X-ray flux at the 2-10 keV band and the VHE gamma-ray flux above 200 GeV, consistent with the gamma-rays being produced by inverse-Compton scattering in the Klein-Nishina regime in the framework of SSC models. The one-zone SSC model can describe the SED of each day for the 13 consecutive days reasonably well, which once more shows the success of this standard theoretical scenario to describe the SEDs of VHE BL Lacs such as Mrk 421. This flaring activity is also very well described by a two-zone SSC model, where one zone is responsible for the quiescent emission, while the other smaller zone, which is spatially separated from the first, contributes to the daily variable emission occurring at X-rays and VHE gamma-rays. The second blob is assumed to have a smaller volume and a narrow electron energy distribution with 3 x 10(4) < gamma < 6 x 10(5), where. is the Lorentz factor of the electrons. Such a two-zone scenario would naturally lead to the correlated variability at the X-ray and VHE bands without variability at the optical/UV band, as well as to shorter timescales for the variability at the X-ray and VHE bands with respect to the variability at the other bands.
Conclusions. Both the one-zone and the two-zone SSC models can describe the daily SEDs via the variation of only four or five model parameters, under the hypothesis that the variability is associated mostly with the underlying particle population. This shows that the particle acceleration and cooling mechanism that produces the radiating particles might be the main mechanism responsible for the broadband SED variations during the flaring episodes in blazars. The two-zone SSC model provides a better agreement with the observed SED at the narrow peaks of the low-and high-energy bumps during the highest activity, although the reported one-zone SSC model could be further improved by varying the parameters related to the emitting region itself (delta, B and R), in addition to the parameters related to the particle population.
KW - radiation mechanisms: non-thermal
KW - galaxies: active
KW - BL Lacertae objects: individual: Mrk 421
KW - gamma rays: galaxies
Y1 - 2015
U6 - http://dx.doi.org/10.1051/0004-6361/201424811
SN - 0004-6361 (print)
SN - 1432-0746 (online)
VL - 578
PB - EDP Sciences
CY - Les Ulis
ER -
TY - JOUR
A1 - Orienti, M.
A1 - Finke, J.
A1 - Raiteri, C. M.
A1 - Hovatta, T.
A1 - Larsson, J.
A1 - Max-Moerbeck, W.
A1 - Perkins, J.
A1 - Readhead, A. C. S.
A1 - Richards, J. L.
A1 - Beilicke, M.
A1 - Benbow, W.
A1 - Berger, K.
A1 - Bird, R.
A1 - Bugaev, V.
A1 - Cardenzana, J. V.
A1 - Cerruti, M.
A1 - Chen, Xuhui
A1 - Ciupik, L.
A1 - Dickinson, H. J.
A1 - Eisch, J. D.
A1 - Errando, M.
A1 - Falcone, A.
A1 - Finley, J. P.
A1 - Fleischhack, H.
A1 - Fortin, P.
A1 - Fortson, L.
A1 - Furniss, A.
A1 - Gerard, L.
A1 - Gillanders, G. H.
A1 - Griffiths, S. T.
A1 - Grube, J.
A1 - Gyuk, G.
A1 - Hakansson, Nils
A1 - Holder, J.
A1 - Humensky, T. B.
A1 - Kar, P.
A1 - Kertzman, M.
A1 - Khassen, Y.
A1 - Kieda, D.
A1 - Krennrich, F.
A1 - Kumar, S.
A1 - Lang, M. J.
A1 - Maier, G.
A1 - McCann, A.
A1 - Meagher, K.
A1 - Moriarty, P.
A1 - Mukherjee, R.
A1 - Nieto, D.
A1 - Ong, R. A.
A1 - Otte, A. N.
A1 - Pohl, Manuela
A1 - Popkow, A.
A1 - Prokoph, H.
A1 - Pueschel, E.
A1 - Quinn, J.
A1 - Ragan, K.
A1 - Reynolds, P. T.
A1 - Richards, G. T.
A1 - Roache, E.
A1 - Rousselle, J.
A1 - Santander, M.
A1 - Sembroski, G. H.
A1 - Smith, A. W.
A1 - Staszak, D.
A1 - Telezhinsky, Igor
A1 - Tucci, J. V.
A1 - Tyler, J.
A1 - Varlotta, A.
A1 - Vassiliev, V. V.
A1 - Wakely, S. P.
A1 - Weinstein, A.
A1 - Welsing, R.
A1 - Williams, D. A.
A1 - Zitzer, B.
T1 - The most powerful flaring activity from the NLSyl PMN J0948+0022
JF - Monthly notices of the Royal Astronomical Society
N2 - We report on multifrequency observations performed during 2012 December-2013 August of the first narrow-line Seyfert 1 galaxy detected in gamma-rays, PMN J0948+0022 (z = 0.5846). A y -ray flare was observed by the Large Area Telescope on board Fermi during 2012 December-2013 January, reaching a daily peak flux in the 0.1-100 GeV energy range of (155 31) x 10 8 ph cm(-2) S-1 on 2013 January 1, corresponding to an apparent isotropic luminosity of similar to 1.5 x 1048 erg s(-1). The y -ray flaring period triggered Swift and Very Energetic Radiation Imaging Telescope Array System (VERITAS) observations in addition to radio and optical monitoring by Owens Valley Radio Observatory, Monitoring Of Jets in Active galactic nuclei with VLBA Experiments, and Catalina Real-time Transient Survey. A strong flare was observed in optical, UV, and X-rays on 2012 December 30, quasi-simultaneously to the y -ray flare, reaching a record flux for this source from optical to y gamma-rays. VERITAS observations at very high energy (E > 100 GeV) during 2013 January 6-17 resulted in an upper limit of F>0.2 Trev < 4.0 x 10(-12) ph cm(-2) s(-1). We compared the spectral energy distribution (SED) of the flaring state in 2013 January with that of an intermediate state observed in 2011. The two SEDs, modelled as synchrotron emission and an external Compton scattering of seed photons from a dust torus, can be modelled by changing both the electron distribution parameters and the magnetic field.
KW - galaxies: active-galaxies: individual: PMN J0948+0022
KW - galaxies: nuclei
KW - galaxies: Seyfert
KW - gamma-rays: general
Y1 - 2015
U6 - http://dx.doi.org/10.1093/mnras/stu2251
SN - 0035-8711 (print)
SN - 1365-2966 (online)
VL - 446
IS - 3
SP - 2456
EP - 2467
PB - Oxford Univ. Press
CY - Oxford
ER -
TY - JOUR
A1 - Aliu, E.
A1 - Archer, A.
A1 - Aune, T.
A1 - Barnacka, A.
A1 - Behera, B.
A1 - Beilicke, M.
A1 - Benbow, W.
A1 - Berger, K.
A1 - Bird, R.
A1 - Buckley, J. H.
A1 - Bugaev, V.
A1 - Byrum, K.
A1 - Cardenzana, J. V.
A1 - Cerruti, M.
A1 - Chen, Xuhui
A1 - Ciupik, L.
A1 - Connolly, M. P.
A1 - Cui, Wei
A1 - Dickinson, H. J.
A1 - Dumm, J.
A1 - Eisch, J. D.
A1 - Errando, M.
A1 - Falcone, A.
A1 - Federici, Simone
A1 - Feng, Q.
A1 - Finley, J. P.
A1 - Fortin, P.
A1 - Fortson, L.
A1 - Furniss, A.
A1 - Galante, N.
A1 - Gillanders, G. H.
A1 - Griffin, S.
A1 - Griffiths, S. T.
A1 - Grube, J.
A1 - Gyuk, G.
A1 - Hakansson, Nils
A1 - Hanna, D.
A1 - Holder, J.
A1 - Hughes, G.
A1 - Humensky, T. B.
A1 - Johnson, C. A.
A1 - Kaaret, P.
A1 - Kar, P.
A1 - Kertzman, M.
A1 - Khassen, Y.
A1 - Kieda, D.
A1 - Krawczynski, H.
A1 - Krennrich, F.
A1 - Kumar, S.
A1 - Lang, M. J.
A1 - Madhavan, A.
A1 - McArthur, S.
A1 - McCann, A.
A1 - Meagher, K.
A1 - Millis, J.
A1 - Moriarty, P.
A1 - Nieto, Daniel
A1 - Ong, R. A.
A1 - Orr, M.
A1 - Otte, A. N.
A1 - Park, N.
A1 - Perkins, J. S.
A1 - Pohl, Martin
A1 - Popkow, A.
A1 - Prokoph, H.
A1 - Pueschel, E.
A1 - Quinn, J.
A1 - Ragan, K.
A1 - Rajotte, J.
A1 - Reyes, L. C.
A1 - Reynolds, P. T.
A1 - Richards, G. T.
A1 - Roache, E.
A1 - Sembroski, G. H.
A1 - Shahinyan, K.
A1 - Staszak, D.
A1 - Telezhinsky, I.
A1 - Tucci, J. V.
A1 - Tyler, J.
A1 - Varlotta, A.
A1 - Vassiliev, V. V.
A1 - Wakely, S. P.
A1 - Weinstein, A.
A1 - Welsing, R.
A1 - Wilhelm, Alina
A1 - Williams, D. A.
A1 - Zitzer, B.
T1 - Veritas observations of the BL LAC OBJECT PG 1553+113
JF - The astrophysical journal : an international review of spectroscopy and astronomical physics
N2 - We present results from VERITAS observations of the BL Lac object PG 1553+113 spanning the years 2010, 2011, and 2012. The time-averaged spectrum, measured between 160 and 560 GeV, is well described by a power law with a spectral index of 4.33 +/- 0.09. The time-averaged integral flux above 200 GeV measured for this period was (1.69 +/- 0.06) x 10(-11) photons cm(-2) s(-1), corresponding to 6.9% of the Crab Nebula flux. We also present the combined gamma-ray spectrum from the Fermi Large Area Telescope and VERITAS covering an energy range from 100 MeV to 560 GeV. The data are well fit by a power law with an exponential cutoff at 101.9 +/- 3.2 GeV. The origin of the cutoff could be intrinsic to PG 1553+113 or be due to the gamma-ray opacity of our universe through pair production off the extragalactic background light (EBL). Given lower limits to the redshift of z > 0.395 based on optical/UV observations of PG 1553+113, the cutoff would be dominated by EBL absorption. Conversely, the small statistical uncertainties of the VERITAS energy spectrum have allowed us to provide a robust upper limit on the redshift of PG 1553+113 of z <= 0.62. A strongly elevated mean flux of (2.50 +/- 0.14) x10(-11) photons cm(-2) s(-1) (10.3% of the Crab Nebula flux) was observed during 2012, with the daily flux reaching as high as (4.44 +/- 0.71) x10(-11) photons cm(-2) s(-1) (18.3% of the Crab Nebula flux) on MJD 56048. The light curve measured during the 2012 observing season is marginally inconsistent with a steady flux, giving a chi(2) probability for a steady flux of 0.03%.
KW - BL Lacertae objects: general
Y1 - 2015
U6 - http://dx.doi.org/10.1088/0004-637X/799/1/7
SN - 0004-637X (print)
SN - 1538-4357 (online)
VL - 799
IS - 1
PB - IOP Publ. Ltd.
CY - Bristol
ER -
TY - JOUR
A1 - Aliu, E.
A1 - Archambault, S.
A1 - Archer, A.
A1 - Aune, T.
A1 - Barnacka, A.
A1 - Beilicke, M.
A1 - Benbow, W.
A1 - Bird, R.
A1 - Buckley, J. H.
A1 - Bugaev, V.
A1 - Byrum, K.
A1 - Cardenzana, J. V.
A1 - Cerruti, M.
A1 - Chen, Xuhui
A1 - Ciupik, L.
A1 - Connolly, M. P.
A1 - Cui, W.
A1 - Dickinson, H. J.
A1 - Dumm, J.
A1 - Eisch, J. D.
A1 - Errando, M.
A1 - Falcone, A.
A1 - Feng, Q.
A1 - Finley, J. P.
A1 - Fleischhack, H.
A1 - Fortin, P.
A1 - Fortson, L.
A1 - Furniss, A.
A1 - Gillanders, G. H.
A1 - Griffin, S.
A1 - Griffiths, S. T.
A1 - Grube, J.
A1 - Gyuk, G.
A1 - Kansson, N. H. A.
A1 - Hanna, D.
A1 - Holder, J.
A1 - Humensky, T. B.
A1 - Johnson, C. A.
A1 - Kaaret, P.
A1 - Kar, P.
A1 - Kertzman, M.
A1 - Kieda, D.
A1 - Krennrich, F.
A1 - Kumar, S.
A1 - Lang, M. J.
A1 - Lyutikov, M.
A1 - Madhavan, A. S.
A1 - Maier, G.
A1 - McArthur, S.
A1 - McCann, A.
A1 - Meagher, K.
A1 - Millis, J.
A1 - Moriarty, P.
A1 - Mukherjee, R.
A1 - Nieto, D.
A1 - Ong, R. A.
A1 - Otte, A. N.
A1 - Park, N.
A1 - Pohl, Manuela
A1 - Popkow, A.
A1 - Prokoph, H.
A1 - Pueschel, E.
A1 - Quinn, J.
A1 - Ragan, K.
A1 - Reyes, L. C.
A1 - Reynolds, P. T.
A1 - Richards, G. T.
A1 - Roache, E.
A1 - Santander, M.
A1 - Sembroski, G. H.
A1 - Shahinyan, K.
A1 - Smith, A. W.
A1 - Staszak, D.
A1 - Telezhinsky, Igor
A1 - Tucci, J. V.
A1 - Tyler, J.
A1 - Varlotta, A.
A1 - Vincent, S.
A1 - Wakely, S. P.
A1 - Weinstein, A.
A1 - Williams, D. A.
A1 - Zajczyk, A.
A1 - Zitzer, B.
T1 - A search for pulsations from geminga above 100 GeV with veritas
JF - The astrophysical journal : an international review of spectroscopy and astronomical physics
N2 - We present the results of 71.6 hr of observations of the Geminga pulsar (PSR J0633+1746) with the VERITAS very-high-energy gamma-ray telescope array. Data taken with VERITAS between 2007 November and 2013 February were phase-folded using a Geminga pulsar timing solution derived from data recorded by the XMM-Newton and Fermi-LAT space telescopes. No significant pulsed emission above 100 GeV is observed, and we report upper limits at the 95% confidence level on the integral flux above 135 GeV (spectral analysis threshold) of 4.0x10(-13) s(-1) cm(-2) and 1.7 x 10(-13) s(-1) cm(-2) for the two principal peaks in the emission profile. These upper limits, placed in context with phase-resolved spectral energy distributions determined from 5 yr of data from the Fermi-Large Area Telescope (LAT), constrain possible hardening of the Geminga pulsar emission spectra above similar to 50 GeV.
KW - gamma rays: stars
KW - pulsars: general
KW - pulsars: individual (PSR J0633+1746, Geminga)
Y1 - 2015
U6 - http://dx.doi.org/10.1088/0004-637X/800/1/61
SN - 0004-637X (print)
SN - 1538-4357 (online)
VL - 800
IS - 1
PB - IOP Publ. Ltd.
CY - Bristol
ER -