@article{AliuArchambaultArlenetal.2014,
  author    = {Aliu, E. and Archambault, S. and Arlen, T. 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, 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, S. and Feng, Q. and Finley, J. P. and Fleischhack, H. 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 Johnson, C. A. 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 McArthur, S. and McCann, A. and Meagher, K. and Millis, J. 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 Reyes, L. C. and Reynolds, P. T. and Richards, G. T. and Roache, E. and Sembroski, G. H. and Smith, A. W. and Staszak, D. and Telezhinsky, Igor O. and Theiling, M. and Varlotta, A. and Vassiliev, V. V. and Vincent, S. and Wakely, S. P. and Weekes, T. C. and Weinstein, A. and Welsing, R. and Williams, D. A. and Zajczyk, A. and Zitzer, B.},
  title     = {A three-year multi-wavelenght study of the very-high-energy gamma-ray Blazar 1ES 0229+200},
  series = {The astrophysical journal : an international review of spectroscopy and astronomical physics},
  volume    = {782},
  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/782/1/13},
  pages     = {12},
  year      = {2014},
  language  = {en}
}
@article{ArcherBarnackaBeilickeetal.2014,
  author    = {Archer, A. and Barnacka, Anna and Beilicke, M. and Benbow, W. and Berger, K. and Bird, R. and Biteau, Jonathan and Buckley, J. H. and Bugaev, V. and Byrum, K. and Cardenzana, J. V. and Cerruti, M. and Chen, W. and Chen, Xiaoming and Ciupik, L. and Connolly, M. P. and Cui, W. and Dickinson, H. J. and Dumm, J. and Eisch, J. D. and Falcone, A. and Federici, Simone and Feng, Q. and Finley, J. P. and Fleischhack, H. and Fortson, L. and Furniss, A. and Galante, N. and Griffin, S. and Griffiths, S. T. and Grube, J. and Gyuk, G. and Hakansson, Nils and Hanna, D. and Holder, J. and Hughes, G. and Johnson, C. A. and Kaaret, P. and Kar, P. and Kertzman, M. and Khassen, Y. and Kieda, D. and Krawczynski, H. and Kumar, S. and Lang, M. J. and Maier, G. and McArthur, S. and McCann, A. and Meagher, K. 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, Manuela and Popkow, A. and Prokoph, H. and Pueschel, Elisa 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 Shahinyan, K. and Smith, A. W. and Staszak, D. and Telezhinsky, Igor O. and Tucci, J. V. and Tyler, J. and Varlotta, A. and Vincent, S. and Wakely, S. P. and Weinstein, A. and Welsing, R. and Wilhelm, Alina and Williams, D. A. and Zajczyk, A. and Zitzer, B.},
  title     = {Very-high energy observations of the galactic center region by veritas IN 2010-2012},
  series = {The astrophysical journal : an international review of spectroscopy and astronomical physics},
  volume    = {790},
  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/790/2/149},
  pages     = {9},
  year      = {2014},
  abstract  = {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.},
  language  = {en}
}
@article{AliuArchambaultArcheretal.2016,
  author    = {Aliu, E. and Archambault, S. and Archer, A. and Benbow, W. and Bird, R. and Biteau, Jonathan and Buchovecky, M. and Buckley, J. H. and Bugaev, V. and Byrum, K. and Cardenzana, J. V. and Cerruti, M. and Chen, Xuhui and Ciupik, L. and Connolly, M. P. and Cui, W. and Dickinson, H. J. and Eisch, J. D. and Falcone, A. and Feng, Q. and Finley, J. P. and Fleischhack, H. and Flinders, A. and Fortin, P. and Fortson, L. and Furniss, A. and Gillanders, G. H. and Griffin, S. and Grube, J. and Gyuk, G. and Huetten, M. and Hakansson, Nils and Holder, J. 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 Lang, M. J. and Loo, A. and Maier, G. and McArthur, S. and McCann, A. and Meagher, K. and Moriarty, P. and Mukherjee, R. and Nguyen, T. and Nieto, D. and Ong, R. A. and Otte, A. N. and Pandel, D. and Park, N. and Pelassa, V. and Petrashyk, A. and Pohl, M. and Popkow, A. and Pueschel, Elisa and Quinn, J. and Ragan, K. and Reynolds, P. T. and Richards, G. T. and Roache, E. and Rulten, C. and Santander, M. and Sembroski, G. H. and Shahinyan, K. and Smith, A. W. and Staszak, D. and Telezhinsky, Igor O. and Tucci, J. V. and Tyler, J. and Varlotta, A. and Vincent, S. and Wakely, S. P. and Weiner, O. M. and Weinstein, A. and Wilhelm, Alina and Williams, D. A. and Zitzer, B. and Chernyakova, M. and Roberts, M. S. E.},
  title     = {A SEARCH FOR VERY HIGH ENERGY GAMMA RAYS FROM THE MISSING LINK BINARY PULSAR J1023+0038 WITH VERITAS},
  series = {The astrophysical journal : an international review of spectroscopy and astronomical physics},
  volume    = {831},
  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/831/2/193},
  pages     = {7},
  year      = {2016},
  abstract  = {The binary millisecond radio pulsar PSR J1023+0038 exhibits many characteristics similar to the gamma-ray binary system PSR B1259-63/LS 2883, making it an ideal candidate for the study of high-energy nonthermal emission. It has been the subject of multiwavelength campaigns following the disappearance of the pulsed radio emission in 2013 June, which revealed the appearance of an accretion disk around the neutron star. We present the results of very high energy (VHE) gamma-ray observations carried out by the Very Energetic Radiation Imaging Telescope Array System before and after this change of state. Searches for steady and pulsed emission of both data sets yield no significant gamma-ray signal above 100 GeV, and upper limits are given for both a steady and pulsed gamma-ray flux. These upper limits are used to constrain the magnetic field strength in the shock region of the PSR J1023+0038 system. Assuming that VHE gamma rays are produced via an inverse Compton mechanism in the shock region, we constrain the shock magnetic field to be greater than similar to 2 G before the disappearance of the radio pulsar and greater than similar to 10 G afterward.},
  language  = {en}
}
@article{AliuArchambaultArcheretal.2015,
  author    = {Aliu, E. and Archambault, S. and Archer, A. and Aune, T. and Barnacka, Anna and Beilicke, M. and Benbow, W. and Bird, R. and Buckley, J. H. and Bugaev, V. and Byrum, K. and Cardenzana, J. V. and Cerruti, M. and Chen, Xuhui and Ciupik, L. and Connolly, M. P. and Cui, W. and Dickinson, H. J. and Dumm, J. and Eisch, J. D. and Errando, M. and Falcone, A. and Feng, Q. and Finley, J. P. and Fleischhack, H. and Fortin, P. and Fortson, L. and Furniss, A. and Gillanders, G. H. and Griffin, S. and Griffiths, S. T. and Grube, J. and Gyuk, G. and Kansson, N. H. A. and Hanna, D. and Holder, J. and Humensky, T. B. and Johnson, C. A. and Kaaret, P. and Kar, P. and Kertzman, M. and Kieda, D. and Krennrich, F. and Kumar, S. and Lang, M. J. and Lyutikov, M. and Madhavan, A. S. and Maier, G. and McArthur, S. and McCann, A. and Meagher, K. and Millis, J. and Moriarty, P. and Mukherjee, R. and Nieto, D. and Ong, R. A. and Otte, A. N. and Park, N. and Pohl, Manuela and Popkow, A. and Prokoph, H. and Pueschel, Elisa and Quinn, J. and Ragan, K. and Reyes, L. C. and Reynolds, P. T. and Richards, G. T. and Roache, E. and Santander, M. and Sembroski, G. H. and Shahinyan, K. and Smith, A. W. and Staszak, D. and Telezhinsky, Igor O. and Tucci, J. V. and Tyler, J. and Varlotta, A. and Vincent, S. and Wakely, S. P. and Weinstein, A. and Williams, D. A. and Zajczyk, A. and Zitzer, B.},
  title     = {A search for pulsations from geminga above 100 GeV with veritas},
  series = {The astrophysical journal : an international review of spectroscopy and astronomical physics},
  volume    = {800},
  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/800/1/61},
  pages     = {7},
  year      = {2015},
  abstract  = {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.},
  language  = {en}
}
@article{ArchambaultArcherBenbowetal.2016,
  author    = {Archambault, S. and Archer, A. and Benbow, W. and Bird, R. and Biteau, Jonathan and Buchovecky, M. 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 Eisch, J. D. and Errando, M. and Falcone, A. and Feng, Q. and Finley, J. P. and Fleischhack, H. and Fortin, P. and Fortson, L. and Furniss, A. and Gillanders, G. H. and Griffin, S. and Grube, J. and Gyuk, G. and Huetten, M. and Hakansson, Nils and Hanna, D. and Holder, J. 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 Maier, G. and McArthur, S. and McCann, A. and Meagher, K. and Moriarty, P. and Mukherjee, R. and Nguyen, T. and Nieto, D. and Ong, R. A. and Otte, A. N. and Park, N. and Perkins, J. S. and Pichel, A. and Pohl, Martin and Popkow, A. and Pueschel, Elisa and Quinn, J. and Ragan, K. and Reynolds, P. T. and Richards, G. T. and Roache, E. and Rovero, A. C. and Santander, M. and Sembroski, G. H. and Shahinyan, K. and Smith, A. W. and Staszak, D. and Telezhinsky, Igor O. and Tucci, J. V. and Tyler, J. and Vincent, S. and Wakely, S. P. and Weiner, O. M. and Weinstein, A. and Williams, D. A. and Zitzer, B. and Fumagalli, M. and Prochaska, J. X.},
  title     = {UPPER LIMITS FROM FIVE YEARS OF BLAZAR OBSERVATIONS WITH THE VERITAS CHERENKOV TELESCOPES},
  series = {The astronomical journal},
  volume    = {151},
  journal   = {The astronomical journal},
  publisher = {IOP Publ. Ltd.},
  address   = {Bristol},
  organization    = {VERITAS Collaboration},
  issn      = {0004-6256},
  doi       = {10.3847/0004-6256/151/6/142},
  pages     = {19},
  year      = {2016},
  abstract  = {Between the beginning of its full-scale scientific operations in 2007 and 2012, the VERITAS Cherenkov telescope array observed more than 130 blazars; of these, 26 were detected as very-high-energy (VHE; E > 100 GeV) gamma-ray sources. In this work, we present the analysis results of a sample of 114 undetected objects. The observations constitute a total live-time of similar to 570 hr. The sample includes several unidentified Fermi-Large Area Telescope (LAT) sources (located at high Galactic latitude) as well as all the sources from the second Fermi-LAT catalog that are contained within the field of view of the VERITAS observations. We have also performed optical spectroscopy measurements in order to estimate the redshift of some of these blazars that do not have spectroscopic distance estimates. We present new optical spectra from the Kast instrument on the Shane telescope at the Lick observatory for 18 blazars included in this work, which allowed for the successful measurement or constraint on the redshift of four of them. For each of the blazars included in our sample, we provide the flux upper limit in the VERITAS energy band. We also study the properties of the significance distributions and we present the result of a stacked analysis of the data set, which shows a 4s excess.},
  language  = {en}
}
@article{ArchambaultArlenAuneetal.2014,
  author    = {Archambault, S. and Arlen, T. and Aune, T. and Beilicke, M. and Benbow, W. and Bird, R. and Boettcher, Markus and Bouvier, A. and Buckley, J. H. and Bugaev, V. and Ciupik, L. and Collins-Hughes, E. and Connolly, M. P. and Cui, W. and Dickherber, R. 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 Gall, D. and Garson, A. III. and Gillanders, G. H. and Griffin, S. and Grube, J. and Gusbar, C. and Gyuk, G. and Hanna, D. and Holder, J. and Hughes, G. and Kaaret, P. and Kertzman, M. and Khassen, Y. and Kieda, D. and Krawczynski, H. and Lamerato, A. and Lang, M. J. and Li, 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 Nieto, D. and Ong, R. A. and Orr, M. 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 Reynolds, P. T. and Richards, G. T. and Roache, E. and Roustazadeh, P. and Saxon, D. B. and Sembroski, G. H. and Senturk, G. D. and Skole, C. and Staszak, D. and Telezhinsky, Igor O. and Tesic, G. and Theiling, M. and Varlotta, A. and Vassiliev, V. V. and Vincent, S. and Wakely, S. P. and Weinstein, A. and Welsing, R. and Williams, D. A. and Zitzer, B.},
  title     = {Test of models of the cosmic infrared background with multiwavelength observations of the blazar 1ES 1218+30.4 IN 2009},
  series = {The astrophysical journal : an international review of spectroscopy and astronomical physics},
  volume    = {788},
  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/788/2/158},
  pages     = {9},
  year      = {2014},
  abstract  = {We present the results of a multi-wavelength campaign targeting the blazar 1ES 1218+30.4 with observations with the 1.3 m McGraw-Hill optical telescope, the Rossi X-ray Timing Explorer (RXTE), the Fermi Gamma-Ray Space Telescope, and the Very Energetic Radiation Imaging Telescope Array System (VERITAS). The RXTE and VERITAS observations were spread over a 13 day period and revealed clear evidence for flux variability, and a strong X-ray and gamma-ray flare on 2009 February 26 (MJD 54888). The campaign delivered a well-sampled broadband energy spectrum with simultaneous RXTE and VERITAS very high energy (VHE, > 100 GeV) observations, as well as contemporaneous optical and Fermi observations. The 1ES 1218+30.4 broadband energy spectrum-the first with simultaneous X-ray and VHE gamma-ray energy spectra-is of particular interest as the source is located at a high cosmological redshift for a VHE source (z = 0.182), leading to strong absorption of VHE gamma rays by photons from the optical/infrared extragalactic background light (EBL) via gamma VHE +gamma EBL -> e(+) e(-)pair-creation processes. We model the data with a one-zone synchrotron self-Compton (SSC) emission model and with the extragalactic absorption predicted by several recent EBL models. We find that the observations are consistent with the SSC scenario and all the EBL models considered in this work. We discuss observational and theoretical avenues to improve on the EBL constraints.},
  language  = {en}
}
@article{ArchambaultArcherAuneetal.2016,
  author    = {Archambault, S. and Archer, A. and Aune, T. and Barnacka, Anna and Benbow, W. and Bird, R. and Buchovecky, M. and Buckley, J. H. and Bugaev, V. and Byrum, K. and Cardenzana, J. V. and Cerruti, M. and Chen, Xuhui and Ciupik, L. and Collins-Hughes, E. and Connolly, M. P. and Cui, W. and Dickinson, H. J. and Dumm, J. and Eisch, J. D. and Falcone, A. and Feng, Q. and Finley, J. P. and Fleischhack, H. and Flinders, A. and Fortin, P. and Fortson, L. and Furniss, A. and Gillanders, G. H. and Griffin, S. and Grube, J. and Gyuk, G. and Huetten, M. and Hakansson, Nils and Hanna, D. and Holder, J. and Humensky, T. B. and Johnson, C. A. and Kaaret, P. and Kar, P. and Kelley-Hoskins, N. and Kertzman, M. and Khassen, Y. and Kieda, D. and Krause, M. and Krennrich, F. and Kumar, S. and Lang, M. J. and Maier, G. and McArthur, S. and McCann, A. and Meagher, K. and Millis, J. and Moriarty, P. and Mukherjee, R. and Nieto, D. and Ong, R. A. and Otte, A. N. and Pandel, D. and Park, N. and Pelassa, V. and Pohl, Martin and Popkow, A. and Pueschel, Elisa and Quinn, J. and Ragan, K. and Reynolds, P. T. and Richards, G. T. and Roache, E. and Rousselle, J. and Rulten, C. and Santander, M. and Sembroski, G. H. and Shahinyan, K. and Smith, A. W. and Staszak, D. and Telezhinsky, Igor O. and Tucci, J. V. and Tyler, J. and Vincent, S. and Wakely, S. P. and Weiner, O. M. and Weinstein, A. and Wilhelm, Alina and Williams, D. A. and Zitzer, B.},
  title     = {EXCEPTIONALLY BRIGHT TEV FLARES FROM THE BINARY LS I+61 degrees 303},
  series = {The astrophysical journal : an international review of spectroscopy and astronomical physics ; Part 2, Letters},
  volume    = {817},
  journal   = {The astrophysical journal : an international review of spectroscopy and astronomical physics ; Part 2, Letters},
  publisher = {IOP Publ. Ltd.},
  address   = {Bristol},
  issn      = {2041-8205},
  doi       = {10.3847/2041-8205/817/1/L7},
  pages     = {6},
  year      = {2016},
  abstract  = {The TeV binary system LS I +61 degrees 303 is known for its regular, non-thermal emission pattern that traces the orbital period of the compact object in its 26.5 day orbit around its B0 Ve star companion. The system typically presents elevated TeV emission around apastron passage with flux levels between 5\% and 15\% of the steady flux from the Crab Nebula (> 300 GeV). In this article, VERITAS observations of LS I + 61 degrees. 303 taken in late 2014 are presented, during which bright TeV flares around apastron at flux levels peaking above 30\% of the Crab Nebula flux were detected. This is the brightest such activity from this source ever seen in the TeV regime. The strong outbursts have rise and fall times of less than a day. The short timescale of the flares, in conjunction with the observation of 10 TeV photons from LS I + 61 degrees 303 during the flares, provides constraints on the properties of the accelerator in the source.},
  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}
}
@article{AliuArcherAuneetal.2015,
  author    = {Aliu, E. and Archer, A. and Aune, T. and Barnacka, Anna and Behera, B. and Beilicke, M. and Benbow, W. and Berger, K. and Bird, R. and Buckley, J. H. and Bugaev, V. and Byrum, K. and Cardenzana, J. V. and Cerruti, M. and Chen, Xuhui and Ciupik, L. and Connolly, M. P. and Cui, Wei and Dickinson, H. J. and Dumm, J. and Eisch, J. D. and Errando, M. 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 Hakansson, Nils and Hanna, D. and Holder, J. and Hughes, G. and Humensky, T. B. and Johnson, C. A. and Kaaret, P. and Kar, P. and Kertzman, M. and Khassen, Y. and Kieda, D. and Krawczynski, H. and Krennrich, F. and Kumar, S. and Lang, M. J. and Madhavan, A. and McArthur, S. and McCann, A. and Meagher, K. and Millis, J. and Moriarty, P. and Nieto, Daniel and Ong, R. A. and Orr, M. and Otte, A. N. and Park, N. and Perkins, J. S. and Pohl, Martin and Popkow, A. and Prokoph, H. and Pueschel, Elisa 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 Shahinyan, K. and Staszak, D. and Telezhinsky, Igor O. and Tucci, J. V. and Tyler, J. and Varlotta, A. and Vassiliev, V. V. and Wakely, S. P. and Weinstein, A. and Welsing, R. and Wilhelm, Alina and Williams, D. A. and Zitzer, B.},
  title     = {Veritas observations of the BL LAC OBJECT PG 1553+113},
  series = {The astrophysical journal : an international review of spectroscopy and astronomical physics},
  volume    = {799},
  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/799/1/7},
  pages     = {9},
  year      = {2015},
  abstract  = {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\%.},
  language  = {en}
}
@article{AbeysekaraArcherBenbowetal.2018,
  author    = {Abeysekara, A. U. and Archer, A. and Benbow, Wystan and Bird, Ralph and Brill, A. and Brose, Robert and Buckley, J. H. and Christiansen, Jessie L. and Chromey, A. J. and Daniel, M. K. and Falcone, A. and Feng, Qi and Finley, John P. and Fortson, L. and Furniss, Amy and Gillanders, Gerard H. and Gueta, O. and Hanna, David and Hervet, O. and Holder, J. and Hughes, G. and Humensky, T. B. and Johnson, Caitlin A. and Kaaret, Philip and Kar, P. and Kelley-Hoskins, N. and Kertzman, M. and Kieda, David and Krause, Maria and Krennrich, F. and Lang, M. J. and Moriarty, P. and Mukherjee, Reshmi and Ong, R. A. and Otte, A. N. and Park, N. and Petrashyk, A. and Pohl, Martin and Pueschel, Elisa and Quinn, J. and Ragan, K. and Reynolds, P. T. and Richards, Gregory T. and Roache, E. and Rulten, C. and Sadeh, I. and Santander, Marcos and Scott, S. S. and Sembroski, G. H. and Shahinyan, Karlen and Tyler, J. and Wakely, S. P. and Weinstein, A. and Wells, R. M. and Wilcox, P. and Wilhelm, Alina and Williams, D. A. and Williamson, T. J. and Zitzer, B. and Kaur, A.},
  title     = {VERITAS Observations of the BL Lac Object TXS 0506+056},
  series = {The astrophysical journal : an international review of spectroscopy and astronomical physics ; Part 2, Letters},
  volume    = {861},
  journal   = {The astrophysical journal : an international review of spectroscopy and astronomical physics ; Part 2, Letters},
  number    = {2},
  publisher = {IOP Publ. Ltd.},
  address   = {Bristol},
  organization    = {VERITAS Collaboration},
  issn      = {2041-8205},
  doi       = {10.3847/2041-8213/aad053},
  pages     = {6},
  year      = {2018},
  abstract  = {On 2017 September 22, the IceCube Neutrino Observatory reported the detection of the high-energy neutrino event IC 170922A, of potential astrophysical origin. It was soon determined that the neutrino direction was consistent with the location of the gamma-ray blazar TXS 0506+056. (3FGL J0509.4+ 0541), which was in an elevated gamma-ray emission state as measured by the Fermi satellite. Very Energetic Radiation Imaging Telescope Array System (VERITAS) observations of the neutrino/blazar region started on 2017 September 23 in response to the neutrino alert and continued through 2018 February 6. While no significant very-high-energy (VHE; E > 100 GeV) emission was observed from the blazar by VERITAS in the two-week period immediately following the IceCube alert, TXS 0506+ 056 was detected by VERITAS with a significance of 5.8 standard deviations (sigma) in the full 35 hr data set. The average photon flux of the source during this period was (8.9 +/- 1.6). x. 10(-12) cm(-2) s(-1), or 1.6\% of the Crab Nebula flux, above an energy threshold of 110 GeV, with a soft spectral index of 4.8. +/-. 1.3.},
  language  = {en}
}