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- gamma rays: galaxies (9)
- gamma rays: general (9)
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- astroparticle physics (3)
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- BL Lacertae objects: individual (1ES 0229+200, VER J0232+202) (1)
- BL Lacertae objects: individual (1ES 1959+650=VER J1959+651) (1)
- BL Lacertae objects: individual (B2 1215+30, VER J1217+301) (1)
- BL Lacertae objects: individual (PKS 1424+240)-cosmic background radiation (1)
- BL Lacertae objects: individual (RBS 0413-VER J0319+187) (1)
- BL Lacertae objects: individual (VER J0521+211) (1)
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- ISM: individual objects (Crab Nebula) (1)
- ISM: individual objects (G120.1+01.4, Tycho=VER J0025+641) (1)
- ISM: supernova remnants (1)
- Next generation Cherenkov telescopes (1)
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- X-rays: individual (Cygnus X-3) (1)
- astrobiology (1)
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- black hole physics (1)
- dark matter (1)
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- galaxies: clusters: general (1)
- galaxies: clusters: individual (Coma (ACO 1656)) (1)
- galaxies: individual (M 87) (1)
- galaxies: individual (M 87, VER J1230+123) (1)
- galaxies: individual: 1ES 1741+196=VER J1744+195 (1)
- gamma rays: galaxies: clusters (1)
- gamma rays: general(HESS J0632+057, VER J0633+057) (1)
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- gamma-ray burst: individual (GRB 130427A) (1)
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- novae, cataclysmic variables (1)
- pulsars: individual (PSR J0633+1746, Geminga) (1)
- pulsars: individual (PSR J1023+0038) (1)
- pulsars: individual: B0531+21 (1)
- rays: stars (1)
- relativistic processes (1)
- stars: individual ( KIC 8462852) (1)
- stars: individual (1A 0535+262) (1)
- stars: individual (LS I+61 degrees 303, VER J0240+612) (1)
- supernovae: individual (G0.9+0.1) (1)
- techniques: photometric (1)
- white dwarfs (1)
Institute
Archer, A. ; Barnacka, Anna ; Beilicke, M. ; Benbow, W. ; Berger, K. ; Bird, R. ; Biteau, Jonathan ; Buckley, J. H. ; Bugaev, V. ; Byrum, K. ; Cardenzana, J. V. ; Cerruti, M. ; Chen, W. ; Chen, Xiaoming ; Ciupik, L. ; Connolly, M. P. ; Cui, W. ; Dickinson, H. J. ; Dumm, J. ; Eisch, J. D. ; Falcone, A. ; Federici, Simone ; Feng, Q. ; Finley, J. P. ; Fleischhack, H. ; Fortson, L. ; Furniss, A. ; Galante, N. ; Griffin, S. ; Griffiths, S. T. ; Grube, J. ; Gyuk, G. ; Hakansson, Nils ; Hanna, D. ; Holder, J. ; Hughes, G. ; Johnson, C. A. ; Kaaret, P. ; Kar, P. ; Kertzman, M. ; Khassen, Y. ; Kieda, D. ; Krawczynski, H. ; Kumar, S. ; Lang, M. J. ; Maier, G. ; McArthur, S. ; McCann, A. ; Meagher, K. ; Moriarty, P. ; Mukherjee, R. ; Nieto, D. ; Ong, R. A. ; Otte, A. N. ; Park, N. ; Perkins, J. S. ; Pohl, Manuela ; Popkow, A. ; Prokoph, H. ; Pueschel, Elisa ; Quinn, J. ; Ragan, K. ; Rajotte, J. ; Reyes, L. C. ; Reynolds, P. T. ; Richards, G. T. ; Roache, E. ; Sembroski, G. H. ; Shahinyan, K. ; Smith, A. W. ; Staszak, D. ; Telezhinsky, Igor O. ; Tucci, J. V. ; Tyler, J. ; Varlotta, A. ; Vincent, S. ; Wakely, S. P. ; Weinstein, A. ; Welsing, R. ; Wilhelm, Alina ; Williams, D. A. ; Zajczyk, A. ; Zitzer, B.
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.
Archer, A. ; Benbow, W. ; Bird, R. ; Buchovecky, M. ; Buckley, J. H. ; Bugaev, V. ; Byrum, K. ; Cardenzana, J. V. ; Cerruti, M. ; Chen, Xuhui ; Ciupik, L. ; Collins-Hughes, E. ; Connolly, M. P. ; Eisch, J. D. ; Falcone, A. ; Feng, Q. ; Finley, J. P. ; Fleischhack, H. ; Flinders, A. ; Fortson, L. ; Furniss, A. ; Gillanders, G. H. ; Griffin, S. ; Grube, J. ; Gyuk, G. ; Hakansson, Nils ; Hanna, D. ; Holder, J. ; Humensky, T. B. ; Huetten, M. ; Johnson, C. A. ; Kaaret, P. ; Kar, P. ; Kelley-Hoskins, N. ; Kertzman, M. ; Kieda, D. ; Krause, M. ; Krennrich, F. ; Kumar, S. ; Lang, M. J. ; McArthur, S. ; McCann, A. ; Meagher, K. ; Millis, J. ; Moriarty, P. ; Mukherjee, R. ; Nieto, D. ; Ong, R. A. ; Park, N. ; Pelassa, V. ; Pohl, Martin ; Popkow, A. ; Pueschel, Elisa ; Quinn, J. ; Ragan, K. ; Ratliff, G. ; Reynolds, P. T. ; Richards, G. T. ; Roache, E. ; Rousselle, J. ; Santander, M. ; Sembroski, G. H. ; Shahinyan, K. ; Smith, A. W. ; Staszak, D. ; Telezhinsky, Igor O. ; Tucci, J. V. ; Tyler, J. ; Vassiliev, V. V. ; Wakely, S. P. ; Weiner, O. M. ; Weinstein, A. ; Wilhelm, Alina ; Williams, D. A. ; Zitzer, B. ; Yusef-Zadeh, F.
The Galactic Center ridge has been observed extensively in the past by both GeV and TeV gamma-ray instruments revealing a wealth of structure, including a diffuse component and the point sources G0.9+0.1 (a composite supernova remnant) and Sgr A* (believed to be associated with the supermassive black hole located at the center of our Galaxy). Previous very high energy (VHE) gamma-ray observations with the H.E.S.S.. experiment have also detected an extended TeV gamma-ray component along the Galactic plane in the >300 GeV gamma-ray regime. Here we report on observations of the Galactic Center ridge from 2010 to 2014 by the VERITAS telescope array in the >2 TeV energy range. From these observations we (1) provide improved measurements of the differential energy spectrum for Sgr A* in the >2 TeV gamma-ray regime, (2) provide a detection in the >2 TeV gamma-ray emission from the composite SNR G0.9+0.1 and an improved determination of its multi-TeV gamma-ray energy spectrum, and. (3) report on the detection of VER J1746-289, a localized enhancement of >2 TeV gamma-ray emission along the Galactic plane.
Arlen, T. ; Aune, T. ; Beilicke, M. ; Benbow, W. ; Bouvier, A. ; Buckley, J. H. ; Bugaev, V. ; Byrum, K. ; Cannon, A. ; Cesarini, A. ; Ciupik, L. ; Collins-Hughes, E. ; Connolly, M. P. ; Cui, W. ; Dickherber, R. ; Dumm, J. ; Falcone, A. ; Federici, S. ; Feng, Q. ; Finley, J. P. ; Finnegan, G. ; Fortson, L. ; Furniss, A. ; Galante, N. ; Gall, D. ; Godambe, S. ; Griffin, S. ; Grube, J. ; Gyuk, G. ; Holder, J. ; Huan, H. ; Hughes, G. ; Humensky, T. B. ; Imran, A. ; Kaaret, P. ; Karlsson, N. ; Kertzman, M. ; Khassen, Y. ; Kieda, D. ; Krawczynski, H. ; Krennrich, F. ; Lee, K. ; Madhavan, A. S. ; Maier, G. ; Majumdar, P. ; McArthur, S. ; McCann, A. ; Moriarty, P. ; Mukherjee, R. ; Nelson, T. ; de Bhroithe, A. O'Faolain ; Ong, R. A. ; Orr, M. ; Otte, A. N. ; Park, N. ; Perkins, J. S. ; Pohl, Martin ; Prokoph, H. ; Quinn, J. ; Ragan, K. ; Reyes, L. C. ; Reynolds, P. T. ; Roache, E. ; Ruppel, J. ; Saxon, D. B. ; Schroedter, M. ; Sembroski, G. H. ; Skole, C. ; Smith, A. W. ; Telezhinsky, Igor O. ; Tesic, G. ; Theiling, M. ; Thibadeau, S. ; Tsurusaki, K. ; Varlotta, A. ; Vivier, M. ; Wakely, S. P. ; Ward, J. E. ; Weinstein, A. ; Welsing, R. ; Williams, D. A. ; Zitzer, B. ; Pfrommer, C. ; Pinzke, A.
Observations of radio halos and relics in galaxy clusters indicate efficient electron acceleration. Protons should likewise be accelerated and, on account of weak energy losses, can accumulate, suggesting that clusters may also be sources of very high energy (VHE; E > 100 GeV) gamma-ray emission. We report here on VHE gamma-ray observations of the Coma galaxy cluster with the VERITAS array of imaging Cerenkov telescopes, with complementing Fermi Large Area Telescope observations at GeV energies. No significant gamma-ray emission from the Coma Cluster was detected. Integral flux upper limits at the 99% confidence level were measured to be on the order of (2-5) x 10(-8) photonsm(-2) s(-1) (VERITAS, >220 GeV) and similar to 2 x 10(-6) photonsm(-2) s(-1) (Fermi, 1-3GeV), respectively. We use the gamma-ray upper limits to constrain cosmic rays (CRs) and magnetic fields in Coma. Using an analytical approach, the CR-to-thermal pressure ratio is constrained to be < 16% from VERITAS data and <1.7% from Fermi data (averaged within the virial radius). These upper limits are starting to constrain the CR physics in self-consistent cosmological cluster simulations and cap the maximum CR acceleration efficiency at structure formation shocks to be <50%. Alternatively, this may argue for non-negligible CR transport processes such as CR streaming and diffusion into the outer cluster regions. Assuming that the radio-emitting electrons of the Coma halo result from hadronic CR interactions, the observations imply a lower limit on the central magnetic field in Coma of similar to(2-5.5) mu G, depending on the radial magnetic field profile and on the gamma-ray spectral index. Since these values are below those inferred by Faraday rotation measurements in Coma (for most of the parameter space), this renders the hadronic model a very plausible explanation of the Coma radio halo. Finally, since galaxy clusters are dark matter (DM) dominated, the VERITAS upper limits have been used to place constraints on the thermally averaged product of the total self-annihilation cross section and the relative velocity of the DM particles, <sigma nu >.
tAliu, E. ; Archambault, S. ; Arlen, T. ; Aune, T. ; Beilicke, M. ; Benbow, W. ; Bird, R. ; Bouvier, A. ; Bradbury, S. M. ; Buckley, J. H. ; Bugaev, V. ; Byrum, K. ; Cannon, A. ; Cesarini, A. ; Ciupik, L. ; Collins-Hughes, E. ; Connolly, M. P. ; Cui, W. ; Dickherber, R. ; Duke, C. ; Dumm, J. ; Dwarkadas, Vikram V. ; Errando, M. ; Falcone, A. ; Federici, Simone ; Feng, Q. ; Finley, J. P. ; Finnegan, G. ; Fortson, L. ; Furniss, A. ; Galante, N. ; Gall, D. ; Gillanders, G. H. ; Godambe, S. ; Gotthelf, E. V. ; Griffin, S. ; Grube, J. ; Gyuk, G. ; Hanna, D. ; Holder, J. ; Huan, H. ; Hughes, G. ; Humensky, T. B. ; Kaaret, P. ; Karlsson, N. ; Kertzman, M. ; Khassen, Y. ; Kieda, D. ; Krawczynski, H. ; Krennrich, F. ; Lang, M. J. ; Lee, K. ; Madhavan, A. S. ; Maier, G. ; Majumdar, P. ; McArthur, S. ; McCann, A. ; Millis, J. ; Moriarty, P. ; Mukherjee, R. ; Nelson, T. ; de Bhroithe, A. O'Faolain ; Ong, R. A. ; Orr, M. ; Otte, A. N. ; Pandel, D. ; Park, N. ; Perkins, J. S. ; Pohl, Martin ; Popkow, A. ; Prokoph, H. ; Quinn, J. ; Ragan, K. ; Reyes, L. C. ; Reynolds, P. T. ; Roache, E. ; Rose, H. J. ; Ruppel, Jens ; Saxon, D. B. ; Schroedter, M. ; Sembroski, G. H. ; Sentuerk, G. D. ; Skole, C. ; Telezhinsky, Igor O. ; Tesic, G. ; Theiling, M. ; Thibadeau, S. ; Tsurusaki, K. ; Tyler, J. ; Varlotta, A. ; Vassiliev, V. V. ; Vincent, S. ; Wakely, S. P. ; Ward, J. E. ; Weekes, T. C. ; Weinstein, A. ; Weisgarber, T. ; Welsing, R. ; Williams, D. A. ; Zitzer, B.
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.