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Allen, C. ; Archambault, S. ; Archer, A. ; Benbow, W. ; Bird, R. ; Bourbeau, E. ; Brose, Robert ; Buchovecky, M. ; Buckley, J. H. ; Bugaev, V. ; Cardenzana, J. V. ; Cerruti, M. ; Chen, Xuhui ; Christiansen, J. L. ; Connolly, M. P. ; Cui, W. ; Daniel, M. K. ; Eisch, J. D. ; Falcone, Abe ; Feng, Q. ; Fernandez-Alonso, M. ; Finley, J. P. ; Fleischhack, H. ; Flinders, A. ; Fortson, L. ; Furniss, A. ; Gillanders, G. H. ; Griffin, S. ; Grube, J. ; Huetten, M. ; Hakansson, N. ; Hanna, D. ; Hervet, O. ; Holder, J. ; Hughes, G. ; Humensky, T. B. ; Johnson, C. A. ; Kaaret, P. ; Kar, P. ; Kelley-Hoskins, N. ; Kertzman, M. ; Kieda, D. ; Krause, M. ; Krennrich, F. ; Kumar, S. ; Lang, M. J. ; Maier, G. ; McArthur, S. ; McCann, A. ; Meagher, K. ; Moriarty, P. ; Mukherjee, R. ; Nguyen, T. ; Nieto, D. ; Ong, R. A. ; Otte, A. N. ; Park, N. ; Petrashyk, A. ; Pichel, A. ; Pohl, Martin ; Popkow, A. ; Pueschel, Elisa ; Quinn, J. ; Ragan, K. ; Reynolds, P. T. ; Richards, G. T. ; Roache, E. ; Rovero, A. C. ; Rulten, C. ; Sadeh, I. ; Santander, Marcos ; Sembroski, G. H. ; Shahinyan, K. ; Telezhinsky, Igor O. ; Tucci, J. V. ; Tyler, J. ; Wakely, S. P. ; Weinstein, A. ; Wilhelm, Alina ; Williams, D. A.
We present very-high-energy gamma-ray observations of the BL Lac object 1ES 2344+514 taken by the Very Energetic Radiation Imaging Telescope Array System between 2007 and 2015. 1ES 2344+514 is detected with a statistical significance above the background of 20.8 sigma in 47.2 h (livetime) of observations, making this the most comprehensive very-high-energy study of 1ES 2344+514 to date. Using these observations, the temporal properties of 1ES 2344+514 are studied on short and long times-scales. We fit a constant-flux model to nightly and seasonally binned light curves and apply a fractional variability test to determine the stability of the source on different time-scales. We reject the constant-flux model for the 2007-2008 and 2014-2015 nightly binned light curves and for the long-term seasonally binned light curve at the > 3 sigma level. The spectra of the time-averaged emission before and after correction for attenuation by the extragalactic background light are obtained. The observed time-averaged spectrum above 200 GeV is satisfactorily fitted (x(2)/NDF = 7.89/6) by a power-law function with an index Gamma = 2.46 +/- 0.06(stat) +/- 0.20(sys) and extends to at least 8 TeV. The extragalactic-backgroundlight-deabsorbed spectrum is adequately fit (x(2)/NDF = 6.73/6) by a power-law function with an index Gamma = 2.15 +/- 0.06(stat) +/- 0.20(sys) while an F-test indicates that the power law with an exponential cut-off function provides a marginally better fit (x(2)/NDF = 2.56/5) at the 2.1 sigma level. The source location is found to be consistent with the published radio location and its spatial extent is consistent with a point source.
Discovery of Very-high-energy Emission from RGB J2243+203 and Derivation of Its Redshift Upper Limit
(2017)
Abeysekara, A. U. ; Archambault, S. ; Archer, A. ; Benbow, W. ; Bird, R. ; Brose, Robert ; Buchovecky, M. ; Buckley, J. H. ; Bugaev, V. ; Cerruti, M. ; Connolly, M. P. ; Cui, W. ; Falcone, A. ; Feng, Q. ; Finley, J. P. ; Fleischhack, H. ; Fortson, L. ; Furniss, A. ; Gillanders, G. H. ; Griffin, S. ; Grube, J. ; Huetten, M. ; Hanna, D. ; Hervet, O. ; Holder, J. ; Humensky, T. B. ; Johnson, C. A. ; Kaaret, P. ; Kar, P. ; Kelley-Hoskins, N. ; Kertzman, M. ; Kieda, D. ; Krause, M. ; Krennrich, F. ; Kumar, S. ; Lang, M. J. ; Maier, G. ; McArthur, S. ; Moriarty, P. ; Mukherjee, R. ; Nieto, D. ; Ong, R. A. ; Otte, A. N. ; Park, N. ; Petrashyk, A. ; Pohl, Martin ; Popkow, A. ; Pueschel, Elisa ; Quinn, J. ; Ragan, K. ; Reynolds, P. T. ; Richards, G. T. ; Roache, E. ; Rulten, C. ; Sadeh, I. ; Santander, M. ; Sembroski, G. H. ; Shahinyan, K. ; Staszak, D. ; Telezhinsky, Igor O. ; Tyler, J. ; Vassiliev, V. V. ; Wakely, S. P. ; Weiner, O. M. ; Weinstein, A. ; Wilcox, P. ; Wilhelm, Alina ; Williams, D. A. ; Zitzer, B.
Very-high-energy (VHE; > 100 GeV) gamma-ray emission from the blazar RGB J2243+203 was discovered with the VERITAS Cherenkov telescope array, during the period between 2014 December 21 and 24. The VERITAS energy spectrum from this source can be fitted by a power law with a photon index of 4.6 +/- 0.5, and a flux normalization at 0.15 TeV of (6.3 +/- 1.1) x 10(-10) cm(-2) s(-1) TeV-1. The integrated Fermi-LAT flux from 1 to 100 GeV during the VERITAS detection is (4.1 +/- 0.8) x 10(-8) cm(-2) s(-1), which is an order of magnitude larger than the four-year-averaged flux in the same energy range reported in the 3FGL catalog, (4.0 +/- 0.1 x 10(-9) cm(-2) s(-1)). The detection with VERITAS triggered observations in the X-ray band with the Swift-XRT. However, due to scheduling constraints Swift-XRT observations were performed 67 hr after the VERITAS detection, rather than simultaneously with the VERITAS observations. The observed X-ray energy spectrum between 2 and 10 keV can be fitted with a power law with a spectral index of 2.7 +/- 0.2, and the integrated photon flux in the same energy band is (3.6 +/- 0.6) x 10(-13) cm(-2) s(-1). EBL-model-dependent upper limits of the blazar redshift have been derived. Depending on the EBL model used, the upper limit varies in the range from z < 0.9 to z < 1.1.
Abeysekara, A. U. ; Archambault, S. ; Archer, A. ; Benbow, Wystan ; Bird, Ralph ; Buchovecky, M. ; Buckley, J. H. ; Bugaev, V. ; Byrum, K. ; Cerruti, M. ; Chen, X. ; Ciupik, L. ; Cui, W. ; Dickinson, H. J. ; Eisch, J. D. ; Errando, M. ; Falcone, A. ; Feng, Q. ; Finley, J. P. ; Fleischhack, H. ; Fortson, L. ; Furniss, A. ; Gillanders, G. H. ; Griffin, S. ; Grube, J. ; Hutten, M. ; Hakansson, N. ; Hanna, D. ; Holder, J. ; Humensky, T. B. ; Johnson, C. A. ; Kaaret, P. ; Kar, P. ; Kertzman, M. ; Kieda, D. ; Krause, M. ; Krennrich, F. ; Kumar, S. ; Lang, M. J. ; Maier, G. ; McArthur, S. ; McCann, A. ; Meagher, K. ; Moriarty, P. ; Mukherjee, R. ; Nguyen, T. ; Nieto, D. ; Ong, R. A. ; Otte, A. N. ; Park, N. ; Pelassa, V. ; Pohl, Martin ; Popkow, A. ; Pueschel, Elisa ; Quinn, J. ; Ragan, K. ; Reynolds, P. T. ; Richards, G. T. ; Roache, E. ; Rulten, C. ; Santander, M. ; Sembroski, G. H. ; Shahinyan, K. ; Staszak, D. ; Telezhinsky, Igor O. ; Tucci, J. V. ; Tyler, J. ; Wakely, S. P. ; Weiner, O. M. ; Weinstein, A. ; Wilhelm, Alina ; Williams, D. A. ; Fegan, S. ; Giebels, B. ; Horan, D. ; Berdyugin, A. ; Kuan, J. ; Lindfors, E. ; Nilsson, K. ; Oksanen, A. ; Prokoph, H. ; Reinthal, R. ; Takalo, L. ; Zefi, F.
B2 1215+30 is a BL-Lac-type blazar that was first detected at TeV energies by the MAGIC atmospheric Cherenkov telescopes and subsequently confirmed by the Very Energetic Radiation Imaging Telescope Array System (VERITAS) observatory with data collected between 2009 and 2012. In 2014 February 08, VERITAS detected a large-amplitude flare from B2. 1215+30 during routine monitoring observations of the blazar 1ES. 1218+304, located in the same field of view. The TeV flux reached 2.4 times the Crab Nebula flux with a variability timescale of <3.6 hr. Multiwavelength observations with Fermi-LAT, Swift, and the Tuorla Observatory revealed a correlated high GeV flux state and no significant optical counterpart to the flare, with a spectral energy distribution where the gamma-ray luminosity exceeds the synchrotron luminosity. When interpreted in the framework of a onezone leptonic model, the observed emission implies a high degree of beaming, with Doppler factor delta > 10, and an electron population with spectral index p < 2.3.
Archambault, S. ; Archer, A. ; Benbow, W. ; Bird, Ralph ; Bourbeau, E. ; Bouvier, A. ; Buchovecky, M. ; Bugaev, V. ; Cardenzana, J. V. ; Cerruti, M. ; Ciupik, L. ; Connolly, M. P. ; Cui, W. ; Daniel, M. K. ; Errando, M. ; Falcone, A. ; Feng, Q. ; Finley, J. P. ; Fleischhack, H. ; Fortson, L. ; Furniss, A. ; Gillanders, G. H. ; Griffin, S. ; Hanna, D. ; Hervet, O. ; Holder, J. ; Hughes, G. ; Humensky, T. B. ; Hutten, M. ; Johnson, C. A. ; Kaaret, P. ; Kar, P. ; Kertzman, M. ; Kieda, D. ; Krause, M. ; Lang, M. J. ; Lin, T. T. Y. ; Maier, G. ; McArthur, S. ; Moriarty, P. ; Mukherjee, R. ; Nieto, D. ; Ong, R. A. ; Otte, A. N. ; Park, N. ; Pohl, Martin ; Popkow, A. ; Pueschel, Elisa ; Quinn, J. ; Ragan, K. ; Reynolds, P. T. ; Richards, G. T. ; Roache, E. ; Rulten, C. ; Sadeh, I. ; Sembroski, G. H. ; Shahinyan, K. ; Staszak, D. ; Telezhinsky, Igor O. ; Trepanier, S. ; Wakely, S. P. ; Weinstein, A. ; Wilcox, P. ; Williams, D. A. ; Zitzer, B.
Imaging atmospheric Cherenkov telescopes (IACTs) are equipped with sensitive photomultiplier tube (PMT) cameras. Exposure to high levels of background illumination degrades the efficiency of and potentially destroys these photo-detectors over time, so IACTs cannot be operated in the same configuration in the presence of bright moonlight as under dark skies. Since September 2012, observations have been carried out with the VERITAS IACTs under bright moonlight (defined as about three times the night-sky-background (NSB) of a dark extragalactic field, typically occurring when Moon illumination > 35%) in two observing modes, firstly by reducing the voltage applied to the PMTs and, secondly, with the addition of ultra-violet (UV) bandpass filters to the cameras. This has allowed observations at up to about 30 times previous NSB levels (around 80% Moon illumination), resulting in 30% more observing time between the two modes over the course of a year. These additional observations have already allowed for the detection of a flare from the 1ES 1727 + 502 and for an observing program targeting a measurement of the cosmic-ray positron fraction. We provide details of these new observing modes and their performance relative to the standard VERITAS observations. (C) 2017 Elsevier B.V. All rights reserved.
Archambault, S. ; Archer, A. ; Benbow, Wystan ; Bird, Ralph ; Bourbeau, E. ; Buchovecky, M. ; Buckley, J. H. ; Bugaev, V. ; Cerruti, M. ; Connolly, M. P. ; Cui, W. ; Dwarkadas, Vikram V. ; Errando, M. ; Falcone, A. ; Feng, Q. ; Finley, J. P. ; Fleischhack, H. ; Fortson, L. ; Furniss, A. ; Griffin, S. ; Huetten, M. ; Hanna, D. ; Holder, J. ; Johnson, C. A. ; Kaaret, P. ; Kar, P. ; Kelley-Hoskins, N. ; Kertzman, M. ; Kieda, D. ; Krause, M. ; Kumar, S. ; Lang, M. J. ; Maier, G. ; McArthur, S. ; McCann, A. ; Moriarty, P. ; Mukherjee, R. ; Nieto, D. ; Ong, R. A. ; Otte, A. N. ; Park, Nahee ; Pohl, Martin ; Popkow, A. ; Pueschel, Elisa ; Quinn, J. ; Ragan, K. ; Reynolds, P. T. ; Richards, G. T. ; Roache, E. ; Sadeh, I. ; Santander, M. ; Sembroski, G. H. ; Shahinyan, K. ; Slane, P. ; Staszak, D. ; Telezhinsky, Igor O. ; Trepanier, S. ; Tyler, J. ; Wakely, S. P. ; Weinstein, A. ; Weisgarber, T. ; Wilcox, P. ; Wilhelm, Alina ; Williams, D. A. ; Zitzer, B.
Prospects for Cherenkov Telescope Array Observations of the Young Supernova Remnant RX J1713.7-3946
(2017)
Acero, F. ; Aloisio, R. ; Amans, J. ; Amato, Elena ; Antonelli, L. A. ; Aramo, C. ; Armstrong, T. ; Arqueros, F. ; Asano, Katsuaki ; Ashley, M. ; Backes, M. ; Balazs, C. ; Balzer, A. ; Bamba, Aya ; Barkov, Maxim ; Barrio, J. A. ; Benbow, Wystan ; Bernloehr, K. ; Beshley, V. ; Bigongiari, C. ; Biland, A. ; Bilinsky, A. ; Bissaldi, Elisabetta ; Biteau, J. ; Blanch, O. ; Blasi, P. ; Blazek, J. ; Boisson, C. ; Bonanno, G. ; Bonardi, A. ; Bonavolonta, C. ; Bonnoli, G. ; Braiding, C. ; Brau-Nogue, S. ; Bregeon, J. ; Brown, A. M. ; Bugaev, V. ; Bulgarelli, A. ; Bulik, T. ; Burton, Michael ; Burtovoi, A. ; Busetto, G. ; Bottcher, M. ; Cameron, R. ; Capalbi, M. ; Caproni, Anderson ; Caraveo, P. ; Carosi, R. ; Cascone, E. ; Cerruti, M. ; Chaty, Sylvain ; Chen, A. ; Chen, X. ; Chernyakova, M. ; Chikawa, M. ; Chudoba, J. ; Cohen-Tanugi, J. ; Colafrancesco, S. ; Conforti, V. ; Contreras, J. L. ; Costa, A. ; Cotter, G. ; Covino, Stefano ; Covone, G. ; Cumani, P. ; Cusumano, G. ; Daniel, M. ; Dazzi, F. ; De Angelis, A. ; De Cesare, G. ; De Franco, A. ; De Frondat, F. ; Dal Pino, E. M. de Gouveia ; De Lisio, C. ; Lopez, R. de los Reyes ; De Lotto, B. ; de Naurois, M. ; De Palma, F. ; Del Santo, M. ; Delgado, C. ; della Volpe, D. ; Di Girolamo, T. ; Di Giulio, C. ; Di Pierro, F. ; Di Venere, L. ; Doro, M. ; Dournaux, J. ; Dumas, D. ; Dwarkadas, Vikram V. ; Diaz, C. ; Ebr, J. ; Egberts, Kathrin ; Einecke, S. ; Elsaesser, D. ; Eschbach, S. ; Falceta-Goncalves, D. ; Fasola, G. ; Fedorova, E. ; Fernandez-Barral, A. ; Ferrand, Gilles ; Fesquet, M. ; Fiandrini, E. ; Fiasson, A. ; Filipovic, Miroslav D. ; Fioretti, V. ; Font, L. ; Fontaine, Gilles ; Franco, F. J. ; Freixas Coromina, L. ; Fujita, Yutaka ; Fukui, Y. ; Funk, S. ; Forster, A. ; Gadola, A. ; Lopez, R. Garcia ; Garczarczyk, M. ; Giglietto, N. ; Giordano, F. ; Giuliani, A. ; Glicenstein, J. ; Gnatyk, R. ; Goldoni, P. ; Grabarczyk, T. ; Graciani, R. ; Graham, J. ; Grandi, P. ; Granot, Jonathan ; Green, A. J. ; Griffiths, S. ; Gunji, S. ; Hakobyan, H. ; Hara, S. ; Hassan, T. ; Hayashida, M. ; Heller, M. ; Helo, J. C. ; Hinton, J. ; Hnatyk, B. ; Huet, J. ; Huetten, M. ; Humensky, T. B. ; Hussein, M. ; Horandel, J. ; Ikeno, Y. ; Inada, T. ; Inome, Y. ; Inoue, S. ; Inoue, T. ; Inoue, Y. ; Ioka, K. ; Iori, Maurizio ; Jacquemier, J. ; Janecek, P. ; Jankowsky, D. ; Jung, I. ; Kaaret, P. ; Katagiri, H. ; Kimeswenger, S. ; Kimura, Shigeo S. ; Knodlseder, J. ; Koch, B. ; Kocot, J. ; Kohri, K. ; Komin, N. ; Konno, Y. ; Kosack, K. ; Koyama, S. ; Kraus, Michaela ; Kubo, Hidetoshi ; Mezek, G. Kukec ; Kushida, J. ; La Palombara, N. ; Lalik, K. ; Lamanna, G. ; Landt, H. ; Lapington, J. ; Laporte, P. ; Lee, S. ; Lees, J. ; Lefaucheur, J. ; Lenain, J. -P. ; Leto, Giuseppe ; Lindfors, E. ; Lohse, T. ; Lombardi, S. ; Longo, F. ; Lopez, M. ; Lucarelli, F. ; Luque-Escamilla, Pedro Luis ; Lopez-Coto, R. ; Maccarone, M. C. ; Maier, G. ; Malaguti, G. ; Mandat, D. ; Maneva, G. ; Mangano, S. ; Marcowith, A. ; Marti, J. ; Martinez, M. ; Martinez, G. ; Masuda, S. ; Maurin, G. ; Maxted, N. ; Melioli, Claudio ; Mineo, T. ; Mirabal, N. ; Mizuno, T. ; Moderski, R. ; Mohammed, M. ; Montaruli, T. ; Moralejo, A. ; Mori, K. ; Morlino, G. ; Morselli, A. ; Moulin, E. ; Mukherjee, R. ; Mundell, C. ; Muraishi, H. ; Murase, Kohta ; Nagataki, Shigehiro ; Nagayoshi, T. ; Naito, T. ; Nakajima, D. ; Nakamori, T. ; Nemmen, R. ; Niemiec, Jacek ; Nieto, D. ; Nievas-Rosillo, M. ; Nikolajuk, M. ; Nishijima, K. ; Noda, K. ; Nogues, L. ; Nosek, D. ; Novosyadlyj, B. ; Nozaki, S. ; Ohira, Yutaka ; Ohishi, M. ; Ohm, S. ; Okumura, A. ; Ong, R. A. ; Orito, R. ; Orlati, A. ; Ostrowski, M. ; Oya, I. ; Padovani, Marco ; Palacio, J. ; Palatka, M. ; Paredes, Josep M. ; Pavy, S. ; Persic, M. ; Petrucci, P. ; Petruk, Oleh ; Pisarski, A. ; Pohl, Martin ; Porcelli, A. ; Prandini, E. ; Prast, J. ; Principe, G. ; Prouza, M. ; Pueschel, Elisa ; Puelhofer, G. ; Quirrenbach, A. ; Rameez, M. ; Reimer, O. ; Renaud, M. ; Ribo, M. ; Rico, J. ; Rizi, V. ; Rodriguez, J. ; Fernandez, G. Rodriguez ; Rodriguez Vazquez, J. J. ; Romano, Patrizia ; Romeo, G. ; Rosado, J. ; Rousselle, J. ; Rowell, G. ; Rudak, B. ; Sadeh, I. ; Safi-Harb, S. ; Saito, T. ; Sakaki, N. ; Sanchez, D. ; Sangiorgi, P. ; Sano, H. ; Santander, M. ; Sarkar, S. ; Sawada, M. ; Schioppa, E. J. ; Schoorlemmer, H. ; Schovanek, P. ; Schussler, F. ; Sergijenko, O. ; Servillat, M. ; Shalchi, A. ; Shellard, R. C. ; Siejkowski, H. ; Sillanpaa, A. ; Simone, D. ; Sliusar, V. ; Sol, H. ; Stanic, S. ; Starling, R. ; Stawarz, L. ; Stefanik, S. ; Stephan, M. ; Stolarczyk, T. ; Szanecki, M. ; Szepieniec, T. ; Tagliaferri, G. ; Tajima, H. ; Takahashi, M. ; Takeda, J. ; Tanaka, M. ; Tanaka, S. ; Tejedor, L. A. ; Telezhinsky, Igor O. ; Temnikov, P. ; Terada, Y. ; Tescaro, D. ; Teshima, M. ; Testa, V. ; Thoudam, S. ; Tokanai, F. ; Torres, D. F. ; Torresi, E. ; Tosti, G. ; Townsley, C. ; Travnicek, P. ; Trichard, C. ; Trifoglio, M. ; Tsujimoto, S. ; Vagelli, V. ; Vallania, P. ; Valore, L. ; van Driel, W. ; van Eldik, C. ; Vandenbroucke, Justin ; Vassiliev, V. ; Vecchi, M. ; Vercellone, Stefano ; Vergani, S. ; Vigorito, C. ; Vorobiov, S. ; Vrastil, M. ; Vazquez Acosta, M. L. ; Wagner, S. J. ; Wagner, R. ; Wakely, S. P. ; Walter, R. ; Ward, J. E. ; Watson, J. J. ; Weinstein, A. ; White, M. ; White, R. ; Wierzcholska, A. ; Wilcox, P. ; Williams, D. A. ; Wischnewski, R. ; Wojcik, P. ; Yamamoto, T. ; Yamamoto, H. ; Yamazaki, Ryo ; Yanagita, S. ; Yang, L. ; Yoshida, T. ; Yoshida, M. ; Yoshiike, S. ; Yoshikoshi, T. ; Zacharias, M. ; Zampieri, L. ; Zanin, R. ; Zavrtanik, M. ; Zavrtanik, D. ; Zdziarski, A. ; Zech, Alraune ; Zechlin, Hannes ; Zhdanov, V. ; Ziegler, A. ; Zorn, J.
We perform simulations for future Cherenkov Telescope Array (CTA) observations of RX J1713.7-3946, a young supernova remnant (SNR) and one of the brightest sources ever discovered in very high energy (VHE) gamma rays. Special attention is paid to exploring possible spatial (anti) correlations of gamma rays with emission at other wavelengths, in particular X-rays and CO/H I emission. We present a series of simulated images of RX J1713.7-3946 for CTA based on a set of observationally motivated models for the gamma-ray emission. In these models, VHE gamma rays produced by high-energy electrons are assumed to trace the nonthermal X-ray emission observed by XMM-Newton, whereas those originating from relativistic protons delineate the local gas distributions. The local atomic and molecular gas distributions are deduced by the NANTEN team from CO and H I observations. Our primary goal is to show how one can distinguish the emission mechanism(s) of the gamma rays (i.e., hadronic versus leptonic, or a mixture of the two) through information provided by their spatial distribution, spectra, and time variation. This work is the first attempt to quantitatively evaluate the capabilities of CTA to achieve various proposed scientific goals by observing this important cosmic particle accelerator.
A SEARCH FOR VERY HIGH ENERGY GAMMA RAYS FROM THE MISSING LINK BINARY PULSAR J1023+0038 WITH VERITAS
(2016)
Aliu, E. ; Archambault, S. ; Archer, A. ; Benbow, W. ; Bird, R. ; Biteau, Jonathan ; Buchovecky, M. ; Buckley, J. H. ; Bugaev, V. ; Byrum, K. ; Cardenzana, J. V. ; Cerruti, M. ; Chen, Xuhui ; Ciupik, L. ; Connolly, M. P. ; Cui, W. ; Dickinson, H. J. ; Eisch, J. D. ; Falcone, A. ; Feng, Q. ; Finley, J. P. ; Fleischhack, H. ; Flinders, A. ; Fortin, P. ; Fortson, L. ; Furniss, A. ; Gillanders, G. H. ; Griffin, S. ; Grube, J. ; Gyuk, G. ; Huetten, M. ; Hakansson, Nils ; Holder, J. ; Humensky, T. B. ; Johnson, C. A. ; Kaaret, P. ; Kar, P. ; Kelley-Hoskins, N. ; Kertzman, M. ; Kieda, D. ; Krause, M. ; Lang, M. J. ; Loo, A. ; Maier, G. ; McArthur, S. ; McCann, A. ; Meagher, K. ; Moriarty, P. ; Mukherjee, R. ; Nguyen, T. ; Nieto, D. ; Ong, R. A. ; Otte, A. N. ; Pandel, D. ; Park, N. ; Pelassa, V. ; Petrashyk, A. ; Pohl, M. ; Popkow, A. ; Pueschel, Elisa ; Quinn, J. ; Ragan, K. ; Reynolds, P. T. ; Richards, G. T. ; Roache, E. ; Rulten, C. ; Santander, M. ; 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. ; Weiner, O. M. ; Weinstein, A. ; Wilhelm, Alina ; Williams, D. A. ; Zitzer, B. ; Chernyakova, M. ; Roberts, M. S. E.
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.
Archambault, S. ; Archer, A. ; Benbow, W. ; Bird, R. ; Biteau, Jonathan ; Buchovecky, M. ; Buckley, J. H. ; Bugaev, V. ; Byrum, K. ; Cerruti, M. ; Chen, Xuhui ; Ciupik, L. ; Connolly, M. P. ; Cui, W. ; Eisch, J. D. ; Errando, M. ; Falcone, A. ; Feng, Q. ; Finley, J. P. ; Fleischhack, H. ; Fortin, P. ; Fortson, L. ; Furniss, A. ; Gillanders, G. H. ; Griffin, S. ; Grube, J. ; Gyuk, G. ; Huetten, M. ; Hakansson, Nils ; Hanna, D. ; Holder, J. ; Humensky, T. B. ; Johnson, C. A. ; Kaaret, P. ; Kar, P. ; Kelley-Hoskins, N. ; Kertzman, M. ; Kieda, D. ; Krause, M. ; Krennrich, F. ; Kumar, S. ; Lang, M. J. ; Maier, G. ; McArthur, S. ; McCann, A. ; Meagher, K. ; Moriarty, P. ; Mukherjee, R. ; Nguyen, T. ; Nieto, D. ; Ong, R. A. ; Otte, A. N. ; Park, N. ; Perkins, J. S. ; Pichel, A. ; Pohl, Martin ; Popkow, A. ; Pueschel, Elisa ; Quinn, J. ; Ragan, K. ; Reynolds, P. T. ; Richards, G. T. ; Roache, E. ; Rovero, A. C. ; Santander, M. ; Sembroski, G. H. ; Shahinyan, K. ; Smith, A. W. ; Staszak, D. ; Telezhinsky, Igor O. ; Tucci, J. V. ; Tyler, J. ; Vincent, S. ; Wakely, S. P. ; Weiner, O. M. ; Weinstein, A. ; Williams, D. A. ; Zitzer, B. ; Fumagalli, M. ; Prochaska, J. X.
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.
Abeysekara, A. U. ; Archambault, S. ; Archer, A. ; Benbow, W. ; Bird, R. ; Biteau, Jonathan ; Buchovecky, M. ; Buckley, J. H. ; Bugaev, V. ; Byrum, K. ; Cardenzana, J. V. ; Cerruti, M. ; Chen, Xuhui ; Christiansen, J. L. ; Ciupik, L. ; Connolly, M. P. ; Cui, W. ; Dickinson, H. J. ; Dumm, J. ; Eisch, J. D. ; Errando, M. ; Falcone, A. ; Feng, Q. ; Finley, J. P. ; Fleischhack, H. ; Flinders, A. ; Fortin, P. ; Fortson, L. ; Furniss, A. ; Gillanders, G. H. ; Griffin, S. ; Grube, J. ; Gyuk, G. ; Huetten, M. ; Hanna, D. ; Holder, J. ; Humensky, T. B. ; Johnson, C. A. ; Kaaret, P. ; Kar, P. ; Kelley-Hoskins, N. ; Kertzman, M. ; Kieda, D. ; Krause, M. ; Krennrich, F. ; 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. ; Pelassa, V. ; Petrashyk, A. ; Petry, D. ; Pohl, Martin ; Popkow, A. ; Pueschel, Elisa ; Quinn, J. ; Ragan, K. ; Ratliff, G. ; Reyes, L. C. ; Reynolds, P. T. ; Reynolds, K. ; Richards, G. T. ; Roache, E. ; Rulten, C. ; Santander, M. ; Sembroski, G. H. ; Shahinyan, K. ; Smith, A. W. ; Staszak, D. ; Telezhinsky, Igor O. ; Tucci, J. V. ; Tyler, J. ; Vincent, S. ; Wakely, S. P. ; Weiner, O. M. ; Weinstein, A. ; Wilhelm, Alina ; Williams, D. A. ; Zitzer, B.
We present results from multiwavelength observations of the BL Lacertae object 1ES 1741 + 196, including results in the very high energy gamma-ray regime using the Very Energetic Radiation Imaging Telescope Array System (VERITAS). The VERITAS time-averaged spectrum, measured above 180 GeV, is well modelled by a power law with a spectral index of 2.7 +/- 0.7(stat) +/- 0.2(syst). The integral flux above 180 GeV is (3.9 +/- 0.8(stat) +/- 1.0(syst)) x 10(-8) m(-2) s(-1), corresponding to 1.6 per cent of the Crab nebula flux on average. The multiwavelength spectral energy distribution of the source suggests that 1ES 1741+196 is an extreme-high-frequency-peaked BL Lacertae object. The observations analysed in this paper extend over a period of six years, during which time no strong flares were observed in any band. This analysis is therefore one of the few characterizations of a blazar in a non-flaring state.
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.