@article{AbeysekaraArchambaultArcheretal.2017, author = {Abeysekara, A. U. and Archambault, S. and Archer, A. and Benbow, Wystan and Bird, Ralph and Buchovecky, M. and Buckley, J. H. and Bugaev, V. and Byrum, K. and Cerruti, M. and Chen, X. and Ciupik, L. and Cui, W. and Dickinson, H. J. and Eisch, J. D. and Errando, M. and Falcone, A. and Feng, Q. and Finley, J. P. and Fleischhack, H. and Fortson, L. and Furniss, A. and Gillanders, G. H. and Griffin, S. and Grube, J. and Hutten, M. and Hakansson, N. 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 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 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 Rulten, C. and Santander, M. and Sembroski, G. H. and Shahinyan, K. and Staszak, D. and Telezhinsky, Igor O. and Tucci, J. V. and Tyler, J. and Wakely, S. P. and Weiner, O. M. and Weinstein, A. and Wilhelm, Alina and Williams, D. A. and Fegan, S. and Giebels, B. and Horan, D. and Berdyugin, A. and Kuan, J. and Lindfors, E. and Nilsson, K. and Oksanen, A. and Prokoph, H. and Reinthal, R. and Takalo, L. and Zefi, F.}, title = {A Luminous and Isolated Gamma-Ray Flare from the Blazar B2 1215+30}, series = {The astrophysical journal : an international review of spectroscopy and astronomical physics}, volume = {836}, journal = {The astrophysical journal : an international review of spectroscopy and astronomical physics}, number = {2}, publisher = {IOP Publ. Ltd.}, address = {Bristol}, organization = {VERITAS Collaboration;Fermi-LAT Collaboration}, issn = {0004-637X}, doi = {10.3847/1538-4357/836/2/205}, pages = {6}, year = {2017}, abstract = {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.}, language = {en} } @article{ArchambaultArcherBenbowetal.2017, author = {Archambault, S. and Archer, A. and Benbow, W. and Bird, R. and Bourbeau, E. and Brantseg, T. and Buchovecky, M. and Buckley, J. H. and Bugaev, V. and Byrum, K. and Cerruti, M. and Christiansen, J. L. and Connolly, M. P. and Cui, W. and Daniel, M. K. and Feng, Q. and Finley, J. P. and Fleischhack, H. and Fortson, L. and Furniss, A. and Geringer-Sameth, A. and Griffin, S. and Grube, J. and H{\"u}tten, M. and Hakansson, N. and Hanna, D. and Hervet, O. and Holder, J. and Hughes, G. and Hummensky, B. and Johnson, C. A. and Kaaret, P. and Kar, P. and Kelley-Hoskins, N. and Kertzman, M. and Kieda, D. and Koushiappas, S. and Krause, M. and Krennrich, F. and Lang, M. J. and Lin, T. T. Y. and McArthur, S. and Moriarty, P. and Mukherjee, R. and Nieto, D. and Ong, R. A. and Otte, A. N. and Park, N. 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 Sadeh, I. and Santander, M. and Sembroski, G. H. and Shahinyan, K. and Smith, A. W. and Staszak, D. and Telezhinsky, Igor O. and Trepanier, S. and Tucci, J. V. and Tyler, J. and Wakely, S. P. and Weinstein, A. and Wilcox, P. and Williams, D. A. and Zitzer, B.}, title = {Dark matter constraints from a joint analysis of dwarf Spheroidal galaxy observations with VERITAS}, series = {Physical review : D, Particles, fields, gravitation, and cosmology}, volume = {95}, journal = {Physical review : D, Particles, fields, gravitation, and cosmology}, number = {8}, publisher = {American Physical Society}, address = {College Park}, organization = {VERITAS Collaboration}, issn = {2470-0010}, doi = {10.1103/PhysRevD.95.082001}, pages = {14}, year = {2017}, abstract = {We present constraints on the annihilation cross section of weakly interacting massive particles dark matter based on the joint statistical analysis of four dwarf galaxies with VERITAS. These results are derived from an optimized photon weighting statistical technique that improves on standard imaging atmospheric Cherenkov telescope (IACT) analyses by utilizing the spectral and spatial properties of individual photon events. We report on the results of similar to 230 hours of observations of five dwarf galaxies and the joint statistical analysis of four of the dwarf galaxies. We find no evidence of gamma-ray emission from any individual dwarf nor in the joint analysis. The derived upper limit on the dark matter annihilation cross section from the joint analysis is 1.35 x 10(-23) cm(3) s(-1) at 1 TeV for the bottom quark (b (b) over bar) final state, 2.85 x 10(-24) cm(3) s(-1) at 1 TeV for the tau lepton (tau+tau(-)) final state and 1.32 x 10-25 cm(3) s(-1) at 1 TeV for the gauge boson (gamma gamma) final state.}, language = {en} } @article{ArchambaultArcherBenbowetal.2017, author = {Archambault, S. and Archer, A. and Benbow, W. and Bird, Ralph and Bourbeau, E. and Bouvier, A. and Buchovecky, M. and Bugaev, V. and Cardenzana, J. V. and Cerruti, M. and Ciupik, L. and Connolly, M. P. and Cui, W. and Daniel, M. K. and Errando, M. and Falcone, A. and Feng, Q. and Finley, J. P. and Fleischhack, H. and Fortson, L. and Furniss, A. and Gillanders, G. H. and Griffin, S. and Hanna, D. and Hervet, O. and Holder, J. and Hughes, G. and Humensky, T. B. and Hutten, M. and Johnson, C. A. and Kaaret, P. and Kar, P. and Kertzman, M. and Kieda, D. and Krause, M. and Lang, M. J. and Lin, T. T. Y. and Maier, G. and McArthur, S. and Moriarty, P. and Mukherjee, R. and Nieto, D. and Ong, R. A. and Otte, A. N. and Park, N. 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 Rulten, C. and Sadeh, I. and Sembroski, G. H. and Shahinyan, K. and Staszak, D. and Telezhinsky, Igor O. and Trepanier, S. and Wakely, S. P. and Weinstein, A. and Wilcox, P. and Williams, D. A. and Zitzer, B.}, title = {Gamma-ray observations under bright moonlight with VERITAS}, series = {Astroparticle physics}, volume = {91}, journal = {Astroparticle physics}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0927-6505}, doi = {10.1016/j.astropartphys.2017.03.001}, pages = {34 -- 43}, year = {2017}, abstract = {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.}, language = {en} } @article{AhnenAnsoldiAntonellietal.2017, author = {Ahnen, M. L. and Ansoldi, S. and Antonelli, L. A. and Antoranz, P. and Babic, A. and Banerjee, B. and Bangale, P. and de Almeida, U. Barres and Barrio, J. A. and Gonzalez, J. Becerra and Bednarek, W. and Bernardini, E. and Berti, A. and Biasuzzi, B. and Biland, A. and Blanch, O. and Bonnefoy, S. and Bonnoli, G. and Borracci, F. and Bretz, T. and Buson, S. and Carosi, A. and Chatterjee, A. and Clavero, R. and Colin, P. and Colombo, E. and Contreras, J. L. and Cortina, J. and Covino, S. and Da Vela, P. and Dazzi, F. and De Angelis, A. and De Lotto, B. and Wilhelmi, E. de Ona and Di Pierro, F. and Doert, M. and Dominguez, A. and Prester, D. Dominis and Dorner, D. and Doro, M. and Einecke, S. and Glawion, D. Eisenacher and Elsaesser, D. and Engelkemeier, M. and Ramazani, V. Fallah and Fernandez-Barral, A. and Fidalgo, D. and Fonseca, M. V. and Font, L. and Frantzen, K. and Fruck, C. and Galindo, D. and Lopez, R. J. Garcia and Garczarczyk, M. and Terrats, D. Garrido and Gaug, M. and Giammaria, P. and Godinovic, N. and Gonzalez Munoz, A. and Gora, D. and Guberman, D. and Hadasch, D. and Hahn, A. and Hanabata, Y. and Hayashida, M. and Herrera, J. and Hose, J. and Hrupec, D. and Hughes, G. and Idec, W. and Kodani, K. and Konno, Y. and Kubo, H. and Kushida, J. and La Barbera, A. and Lelas, D. and Lindfors, E. and Lombardi, S. and Longo, F. and Lopez, M. and Lopez-Coto, R. and Majumdar, P. and Makariev, M. and Mallot, K. and Maneva, G. and Manganaro, M. and Mannheim, K. and Maraschi, L. and Marcote, B. and Mariotti, M. and Martinez, M. and Mazin, D. and Menzel, U. and Miranda, J. M. and Mirzoyan, R. and Moralejo, A. and Moretti, E. and Nakajima, D. and Neustroev, V. and Niedzwiecki, A. and Rosillo, M. Nievas and Nilsson, K. and Nishijima, K. and Noda, K. and Nogues, L. and Overkemping, A. and Paiano, S. and Palacio, J. and Palatiello, M. and Paneque, D. and Paoletti, R. and Paredes, J. M. and Paredes-Fortuny, X. and Pedaletti, G. and Peresano, M. and Perri, L. and Persic, M. and Poutanen, J. and Moroni, P. G. Prada and Prandini, E. and Puljak, I. and Reichardt, I. and Rhode, W. and Ribo, M. and Rico, J. and Rodriguez Garcia, J. and Saito, T. and Satalecka, K. and Schroder, S. and Schultz, C. and Schweizer, T. and Shore, S. N. and Sillanpaa, A. and Sitarek, J. and Snidaric, I. and Sobczynska, D. and Stamerra, A. and Steinbring, T. and Strzys, M. and Suric, T. and Takalo, L. and Tavecchio, F. and Temnikov, P. and Terzic, T. and Tescaro, D. and Teshima, M. and Thaele, J. and Torres, D. F. and Toyama, T. and Treves, A. and Vanzo, G. and Verguilov, V. and Vovk, I. and Ward, J. E. and Will, M. and Wu, M. H. and Zanin, R. and Abeysekara, A. U. and Archambault, S. and Archer, A. and Benbow, W. and Bird, R. and Buchovecky, M. and Buckley, J. H. and Bugaev, V. and Connolly, M. P. and Cui, W. and Dickinson, H. J. and Falcone, A. and Feng, Q. and Finley, J. P. and Fleischhack, H. and Flinders, A. and Fortson, L. and Gillanders, G. H. and Griffin, S. and Grube, J. and Huetten, M. and Hanna, D. and Holder, J. and Humensky, T. B. and Kaaret, P. and Kar, P. and Kelley-Hoskins, N. and Kertzman, M. and Kieda, D. and Krause, M. and Krennrich, F. and Lang, M. J. and Maier, G. and McCann, A. and Moriarty, P. and Mukherjee, R. and Nieto, D. and Ong, R. A. and Otte, N. and Park, N. and Perkins, J. and Pichel, 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 Rovero, A. C. and Rulten, C. and Sadeh, I. and Santander, M. and Sembroski, G. H. and Shahinyan, K. and Telezhinsky, Igor O. and Tucci, J. V. and Tyler, J. and Wakely, S. P. and Weinstein, A. and Wilcox, P. and Wilhelm, Alina and Williams, D. A. and Zitzer, B. and Razzaque, S. and Villata, M. and Raiteri, C. M. and Aller, H. D. and Aller, M. F. and Larionov, V. M. and Arkharov, A. A. and Blinov, D. A. and Efimova, N. V. and Grishina, T. S. and Hagen-Thorn, V. A. and Kopatskaya, E. N. and Larionova, L. V. and Larionova, E. G. and Morozova, D. A. and Troitsky, I. S. and Ligustri, R. and Calcidese, P. and Berdyugin, A. and Kurtanidze, O. M. and Nikolashvili, M. G. and Kimeridze, G. N. and Sigua, L. A. and Kurtanidze, S. O. and Chigladze, R. A. and Chen, W. P. and Koptelova, E. and Sakamoto, T. and Sadun, A. C. and Moody, J. W. and Pace, C. and Pearson, R. and Yatsu, Y. and Mori, Y. and Carraminyana, A. and Carrasco, L. and de la Fuente, E. and Norris, J. P. and Smith, P. S. and Wehrle, A. and Gurwell, M. A. and Zook, A. and Pagani, C. and Perri, M. and Capalbi, M. and Cesarini, A. and Krimm, H. A. and Kovalev, Y. Y. and Kovalev, Yu. A. and Ros, E. and Pushkarev, A. B. and Lister, M. L. and Sokolovsky, K. V. and Kadler, M. and Piner, G. and Lahteenmaki, A. and Tornikoski, M. and Angelakis, E. and Krichbaum, T. P. and Nestoras, I. and Fuhrmann, L. and Zensus, J. A. and Cassaro, P. and Orlati, A. and Maccaferri, G. and Leto, P. and Giroletti, M. and Richards, J. L. and Max-Moerbeck, W. and Readhead, A. C. S.}, title = {Multiband variability studies and novel broadband SED modeling of Mrk 501 in 2009}, series = {Astronomy and astrophysics : an international weekly journal}, volume = {603}, journal = {Astronomy and astrophysics : an international weekly journal}, publisher = {EDP Sciences}, address = {Les Ulis}, organization = {MAGIC Collaboration;VERITAS Collaboration}, issn = {1432-0746}, doi = {10.1051/0004-6361/201629540}, pages = {30}, year = {2017}, abstract = {Aims. We present an extensive study of the BL Lac object Mrk 501 based on a data set collected during the multi-instrument campaign spanning from 2009 March 15 to 2009 August 1, which includes, among other instruments, MAGIC, VERITAS, Whipple 10 m, and Fermi-LAT to cover the gamma-ray range from 0.1 GeV to 20 TeV; RXTE and Swift to cover wavelengths from UV to hard X-rays; and GASP-WEBT, which provides coverage of radio and optical wavelengths. Optical polarization measurements were provided for a fraction of the campaign by the Steward and St. Petersburg observatories. We evaluate the variability of the source and interband correlations, the gamma-ray flaring activity occurring in May 2009, and interpret the results within two synchrotron self-Compton (SSC) scenarios. Methods. The multiband variability observed during the full campaign is addressed in terms of the fractional variability, and the possible correlations are studied by calculating the discrete correlation function for each pair of energy bands where the significance was evaluated with dedicated Monte Carlo simulations. The space of SSC model parameters is probed following a dedicated grid-scan strategy, allowing for a wide range of models to be tested and offering a study of the degeneracy of model-to-data agreement in the individual model parameters, hence providing a less biased interpretation than the "single-curve SSC model adjustment" typically reported in the literature. Results. We find an increase in the fractional variability with energy, while no significant interband correlations of flux changes are found on the basis of the acquired data set. The SSC model grid-scan shows that the flaring activity around May 22 cannot be modeled adequately with a one-zone SSC scenario (using an electron energy distribution with two breaks), while it can be suitably described within a two (independent) zone SSC scenario. Here, one zone is responsible for the quiescent emission from the averaged 4.5-month observing period, while the other one, which is spatially separated from the first, dominates the flaring emission occurring at X-rays and very-high-energy (> 100 GeV, VHE) gamma-rays. The flaring activity from May 1, which coincides with a rotation of the electric vector polarization angle (EVPA), cannot be satisfactorily reproduced by either a one-zone or a two-independent-zone SSC model, yet this is partially affected by the lack of strictly simultaneous observations and the presence of large flux changes on sub-hour timescales (detected at VHE gamma rays). Conclusions. The higher variability in the VHE emission and lack of correlation with the X-ray emission indicate that, at least during the 4.5-month observing campaign in 2009, the highest energy (and most variable) electrons that are responsible for the VHE gamma rays do not make a dominant contribution to the similar to 1 keV emission. Alternatively, there could be a very variable component contributing to the VHE gamma-ray emission in addition to that coming from the SSC scenario. The studies with our dedicated SSC grid-scan show that there is some degeneracy in both the one-zone and the two-zone SSC scenarios probed, with several combinations of model parameters yielding a similar model-to-data agreement, and some parameters better constrained than others. The observed gamma-ray flaring activity, with the EVPA rotation coincident with the first gamma-ray flare, resembles those reported previously for low frequency peaked blazars, hence suggesting that there are many similarities in the flaring mechanisms of blazars with different jet properties.}, language = {en} } @article{AbeysekaraBenbowBirdetal.2018, author = {Abeysekara, A. U. and Benbow, Wystan and Bird, Ralph and Brantseg, T. and Brose, Robert and Buchovecky, M. and Buckley, J. H. and Bugaev, V. and Connolly, M. P. and Cui, Wei 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 Gunawardhana, Isuru and Huetten, M. 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 Kertzman, M. and Krennrich, F. and Lang, M. J. and Lin, T. T. Y. and McArthur, S. and Moriarty, P. and Mukherjee, Reshmi and Ong, R. A. and Otte, Adam Nepomuk 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, M. and Sembroski, G. H. and Shahinyan, Karlen and Wakely, S. P. and Weinstein, A. and Wells, R. M. and Wilcox, P. and Williams, D. A. and Zitzer, B. and Jorstad, Svetlana G. and Marscher, Alan P. and Lister, Matthew L. and Kovalev, Yuri Y. and Pushkarev, A. B. and Savolainen, Tuomas and Agudo, I. and Molina, S. N. and Gomez, J. L. and Larionov, Valeri M. and Borman, G. A. and Mokrushina, A. A. and Tornikoski, Merja and Lahteenmaki, A. and Chamani, W. and Enestam, S. and Kiehlmann, S. and Hovatta, Talvikki and Smith, P. S. and Pontrelli, P.}, title = {Multiwavelength Observations of the Blazar BL Lacertae}, series = {The astrophysical journal : an international review of spectroscopy and astronomical physics}, volume = {856}, journal = {The astrophysical journal : an international review of spectroscopy and astronomical physics}, number = {2}, publisher = {IOP Publ. Ltd.}, address = {Bristol}, organization = {VERITAS Collaboration}, issn = {0004-637X}, doi = {10.3847/1538-4357/aab35c}, pages = {14}, year = {2018}, abstract = {Combined with measurements made by very-long-baseline interferometry, the observations of fast TeV gamma-ray flares probe the structure and emission mechanism of blazar jets. However, only a handful of such flares have been detected to date, and only within the last few years have these flares been observed from lower-frequency-peaked BL. Lac objects and flat-spectrum radio quasars. We report on a fast TeV gamma-ray flare from the blazar BL. Lacertae observed by the Very Energetic Radiation Imaging Telescope Array System (VERITAS). with a rise time of similar to 2.3 hr and a decay time of similar to 36 min. The peak flux above 200 GeV is (4.2 +/- 0.6) x 10(-6) photon m(-2) s(-1) measured with a 4-minute-binned light curve, corresponding to similar to 180\% of the flux that is observed from the Crab Nebula above the same energy threshold. Variability contemporaneous with the TeV gamma-ray flare was observed in GeV gamma-ray, X-ray, and optical flux, as well as in optical and radio polarization. Additionally, a possible moving emission feature with superluminal apparent velocity was identified in Very Long Baseline Array observations at 43 GHz, potentially passing the radio core of the jet around the time of the gamma-ray flare. We discuss the constraints on the size, Lorentz factor, and location of the emitting region of the flare, and the interpretations with several theoretical models that invoke relativistic plasma passing stationary shocks.}, language = {en} } @article{AbeysekaraArcherBenbowetal.2018, author = {Abeysekara, A. U. and Archer, A. and Benbow, Wystan and Bird, Ralph and Brose, Robert and Buchovecky, M. and Bugaev, V. and Connolly, M. P. and Cui, Wei and Errando, Manel and Falcone, A. and Feng, Qi and Finley, John P. and Flinders, A. and Fortson, L. and Furniss, Amy and Gillanders, Gerard H. and Huetten, M. 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 Lin, T. T. Y. and Maier, Gernot and McArthur, S. and Moriarty, P. and Mukherjee, Reshmi and Ong, R. A. and Park, N. and Perkins, Jeremy S. and Petrashyk, A. and Pohl, Martin and Popkow, Alexis and Pueschel, Elisa and Quinn, J. and Ragan, K. and Reynolds, P. T. and Richards, Gregory T. and Roache, E. and Rulten, C. and Sadeh, I. and Santander, M. and Sembroski, G. H. and Shahinyan, Karlen and Tyler, J. and Wakely, S. P. and Weiner, O. M. and Weinstein, A. and Wells, R. M. and Wilcox, P. and Wilhelm, Alina and Williams, David A. and Zitzer, B. and Vurm, Indrek and Beloborodov, Andrei}, title = {A Strong Limit on the Very-high-energy Emission from GRB 150323A}, series = {The astrophysical journal : an international review of spectroscopy and astronomical physics}, volume = {857}, journal = {The astrophysical journal : an international review of spectroscopy and astronomical physics}, number = {1}, publisher = {IOP Publ. Ltd.}, address = {Bristol}, organization = {VERITAS Collaboration}, issn = {0004-637X}, doi = {10.3847/1538-4357/aab371}, pages = {6}, year = {2018}, abstract = {On 2015 March 23, the Very Energetic Radiation Imaging Telescope Array System (VERITAS) responded to a Swift-Burst Alert Telescope (BAT) detection of a gamma-ray burst, with observations beginning 270 s after the onset of BAT emission, and only 135 s after the main BAT emission peak. No statistically significant signal is detected above 140 GeV. The VERITAS upper limit on the fluence in a 40-minute integration corresponds to about 1\% of the prompt fluence. Our limit is particularly significant because the very-high-energy (VHE) observation started only similar to 2 minutes after the prompt emission peaked, and Fermi-Large Area Telescope observations of numerous other bursts have revealed that the high-energy emission is typically delayed relative to the prompt radiation and lasts significantly longer. Also, the proximity of GRB 150323A (z = 0.593) limits the attenuation by the extragalactic background light to similar to 50\% at 100-200 GeV. We conclude that GRB 150323A had an intrinsically very weak high-energy afterglow, or that the GeV spectrum had a turnover below similar to 100 GeV. If the GRB exploded into the stellar wind of a massive progenitor, the VHE non-detection constrains the wind density parameter to be A greater than or similar to 3 x 10(11) g . cm(-1), consistent with a standard Wolf-Rayet progenitor. Alternatively, the VHE emission from the blast wave would be weak in a very tenuous medium such as the interstellar medium, which therefore cannot be ruled out as the environment of GRB 150323A.}, 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} } @article{AbeysekaraArcherAuneetal.2018, author = {Abeysekara, A. U. and Archer, A. and Aune, Taylor and Benbow, Wystan and Bird, Ralph and Brose, Robert and Buchovecky, M. and Bugaev, V. and Cui, Wei and Daniel, M. K. and Falcone, A. and Feng, Qi and Finley, John P. and Fleischhack, H. and Flinders, A. and Fortson, L. and Furniss, Amy and Gotthelf, Eric V. and Grube, J. and Hanna, David and Hervet, O. and Holder, J. and Huang, K. and Hughes, G. and Humensky, T. B. and Huetten, M. and Johnson, Caitlin A. and Kaaret, Philip and Kar, P. and Kelley-Hoskins, N. and Kertzman, M. and Kieda, David and Krause, Maria and Kumar, S. and Lang, M. J. and Lin, T. T. Y. and Maier, Gernot and McArthur, S. and Moriarty, P. and Mukherjee, Reshmi and Ong, R. A. and Otte, Adam Nepomuk and Pandel, Dirk and Park, Nahee and Petrashyk, A. and Pohl, Martin and Popkow, Alexis and Pueschel, Elisa and Quinn, J. and Ragan, K. and Reynolds, P. T. and Richards, Gregory T. and Roache, E. and Rousselle, J. and Rulten, C. and Sadeh, I. and Santander, M. and Sembroski, G. H. and Shahinyan, Karlen and Tyler, J. and Vassiliev, V. V. and Wakely, S. P. and Ward, J. E. and Weinstein, A. and Wells, R. M. and Wilcox, P. and Wilhelm, Alina and Williams, David A. and Zitzer, B.}, title = {A Very High Energy gamma-Ray Survey toward the Cygnus Region of the Galaxy}, series = {The astrophysical journal : an international review of spectroscopy and astronomical physics}, volume = {861}, journal = {The astrophysical journal : an international review of spectroscopy and astronomical physics}, number = {2}, publisher = {IOP Publ. Ltd.}, address = {Bristol}, issn = {0004-637X}, doi = {10.3847/1538-4357/aac4a2}, pages = {33}, year = {2018}, abstract = {We present results from deep observations toward the Cygnus region using 300 hr of very high energy (VHE)gamma-ray data taken with the VERITAS Cerenkov telescope array and over 7 yr of high-energy.-ray data taken with the Fermi satellite at an energy above 1 GeV. As the brightest region of diffuse gamma-ray emission in the northern sky, the Cygnus region provides a promising area to probe the origins of cosmic rays. We report the identification of a potential Fermi-LAT counterpart to VER J2031+415 (TeV J2032+4130) and resolve the extended VHE source VER J2019+368 into two source candidates (VER J2018+367* and VER J2020+368*) and characterize their energy spectra. The Fermi-LAT morphology of 3FGL J2021.0+4031e (the Gamma Cygni supernova remnant) was examined, and a region of enhanced emission coincident with VER J2019+407 was identified and jointly fit with the VERITAS data. By modeling 3FGL J2015.6+3709 as two sources, one located at the location of the pulsar wind nebula CTB 87 and one at the quasar QSO J2015+371, a continuous spectrum from 1 GeV to 10 TeV was extracted for VER J2016+371 (CTB 87). An additional 71 locations coincident with Fermi-LAT sources and other potential objects of interest were tested for VHE gamma-ray emission, with no emission detected and upper limits on the differential flux placed at an average of 2.3\% of the Crab Nebula flux. We interpret these observations in a multiwavelength context and present the most detailed gamma-ray view of the region to date.}, language = {en} } @article{ArcherBenbowBirdetal.2018, author = {Archer, A. and Benbow, Wystan and Bird, Ralph and Brose, Robert and Buchovecky, M. and Bugaev, V and Cui, Wei and Danie, M. K. and Falcone, A. and Feng, Qi and Finley, John P. and Flinders, A. and Fortson, L. and Furniss, Amy and Gillanders, Gerard H. and Huttens, M. 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 Kieda, David and Krause, Maria and Krennrich, F. and Kumar, S. and Lang, M. J. and Lin, T. T. Y. and McArthur, S. and Moriarty, P. and Mukherjee, Reshmi and Nieto, Daniel and Ong, R. A. and Otte, A. N. and Park, Nahee and Petrashyk, A. and Pohl, Martin and Popkow, Alexis and Pueschel, Elisa and Quinn, J. and Ragan, K. and Reynold, P. T. and Richards, Gregory T. and Roache, E. and Rulten, C. and Sadeh, I and Sembroski, G. H. and Shahinyan, Karlen and Tyler, J. and Wakely, S. P. and Weiner, O. M. and Weinstein, A. and Wells, R. M. and Wilcox, P. and Wilhelm, Alina and Williams, David A. and Brisken, W. F. and Pontrelli, P.}, title = {HESS J1943+213}, series = {The astrophysical journal : an international review of spectroscopy and astronomical physics}, volume = {862}, journal = {The astrophysical journal : an international review of spectroscopy and astronomical physics}, number = {1}, publisher = {IOP Publ. Ltd.}, address = {Bristol}, organization = {VERITAS Collaboration}, issn = {0004-637X}, doi = {10.3847/1538-4357/aacbd0}, pages = {15}, year = {2018}, abstract = {HESS J1943+213 is a very high energy (VHE; > 100 GeV) gamma-ray source in the direction of the Galactic plane. Studies exploring the classification of the source are converging toward its identification as an extreme synchrotron BL Lac object. Here we present 38 hr of VERITAS observations of HESS J1943+213 taken over 2 yr. The source is detected with a significance of similar to 20 standard deviations, showing a remarkably stable flux and spectrum in VHE gamma-rays. Multifrequency Very Long Baseline Array (VLBA) observations of the source confirm the extended, jet-like structure previously found in the 1.6 GHz band with the European VLBI Network and detect this component in the 4.6 and 7.3 GHz bands. The radio spectral indices of the core and the jet and the level of polarization derived from the VLBA observations are in a range typical for blazars. Data from VERITAS, Fermi-LAT, Swift-XRT, the FLWO 48 ' telescope, and archival infrared and hard X-ray observations are used to construct and model the spectral energy distribution (SED) of the source with a synchrotron self-Compton model. The well-measured gamma-ray peak of the SED with VERITAS and Fermi-LAT provides constraining upper limits on the source redshift. Possible contribution of secondary gamma-rays from ultra-high-energy cosmic-ray-initiated electromagnetic cascades to the gamma-ray emission is explored, finding that only a segment of the VHE spectrum can be accommodated with this process. A variability search is performed across X-ray and gamma-ray bands. No statistically significant flux or spectral variability is detected.}, language = {en} } @article{ArcherBenbowBirdetal.2018, author = {Archer, A. and Benbow, W. and Bird, R. and Brose, Robert and Buchovecky, M. and Bugaev, V. and Connolly, M. P. and Cui, W. and Daniel, M. K. and Falcone, A. and Feng, Q. and Finley, J. P. and Fleischhack, H. and Fortson, L. and Furniss, A. and Hanna, D. and Hervet, O. and Holder, J. and Hughes, G. and Humensky, T. B. and Hutten, M. and Johnson, C. A. and Kaaret, P. and Kelley-Hoskins, N. and Kieda, D. and Krause, M. and Krennrich, F. and Kumar, S. and Lang, M. J. and Maier, G. and McArthur, S. and Moriarty, P. and Mukherjee, R. and Nieto, D. and Ong, R. A. and Otte, A. N. and Park, N. and Petrashyk, 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 Rulten, C. and Sadeh, I. and Tyler, J. and Wakely, S. P. and Weiner, O. M. and Wilcox, P. and Wilhelm, Alina and Williams, D. A. and Wissel, S. A. and Zitzer, B.}, title = {Measurement of the iron spectrum in cosmic rays by VERITAS}, series = {Physical review : D, Particles, fields, gravitation, and cosmology}, volume = {98}, journal = {Physical review : D, Particles, fields, gravitation, and cosmology}, number = {2}, publisher = {American Physical Society}, address = {College Park}, organization = {VERITAS Collaboration}, issn = {2470-0010}, doi = {10.1103/PhysRevD.98.022009}, pages = {15}, year = {2018}, abstract = {We present a new measurement of the energy spectrum of iron nuclei in cosmic rays from 20 TeV to 500 TeV; The measurement makes use of a template-based analysis method, which, for the first time, is applied to the energy reconstruction of iron-induced air showers recorded by the VERITAS array of imaging atmospheric Cherenkov telescopes. The event selection makes use of the direct Cherenkov light which is emitted by charged particles before the first interaction, as well as other parameters related to the shape of the recorded air shower images. The measured spectrum is well described by a power law dF/dE = f(0) center dot (E/E-0)(-gamma) over the full energy range, with gamma = 2.82 +/- 0.30(stat)(-0.27)(+0.24)(syst) and f(0) = (4.82 +/- 0.98(stat)(-2.70)(+2.12)(syst)) x 10(-7) m(-2) s(-1) TeV-1 sr(-1) at E-0 = 50 TeV, with no indication of a cutoff or spectral break. The measured differential flux is compatible with previous results, with improved statistical uncertainty at the highest energies.}, language = {en} } @article{ArcherBenbowBirdetal.2018, author = {Archer, A. and Benbow, W. and Bird, R. and Brose, Robert and Buchovecky, M. and Buckley, J. H. and Bugaev, V. and Connolly, M. P. and Cui, W. and Daniel, M. K. and Feng, Q. and Finley, J. P. and Fortson, L. and Furniss, A. and Gillanders, G. and Huetten, M. and Hanna, D. and Hervet, O. and Holder, J. and Hughes, G. and Humensky, T. B. and Johnson, C. A. and Kaaret, P. and Kar, P. and Kelley-Hoskins, N. and Kertzman, M. and Kieda, D. and Krause, M. and Krennrich, F. and Kumar, S. and Lang, M. J. and Lin, T. T. Y. and Maier, G. and McArthur, S. and Moriarty, P. and Mukherjee, R. and Ong, R. A. and Otte, A. N. and Petrashyk, A. and Pohl, M. and Pueschel, Elisa and Quinn, J. and Ragan, K. and Reynolds, P. T. and Richards, G. T. and Roache, E. and Rulten, C. and Sadeh, I. and Santander, M. and Sembroski, G. H. and Staszak, D. and Sushch, I. and Wakely, S. P. and Wells, R. M. and Wilcox, P. and Wilhelm, Alina and Williams, D. A. and Williamson, T. J. and Zitzer, B.}, title = {Measurement of cosmic-ray electrons at TeV energies by VERITAS}, series = {Physical review : D, Particles, fields, gravitation, and cosmology}, volume = {98}, journal = {Physical review : D, Particles, fields, gravitation, and cosmology}, number = {6}, publisher = {American Physical Society}, address = {College Park}, organization = {VERITAS Collaboration}, issn = {2470-0010}, doi = {10.1103/PhysRevD.98.062004}, pages = {7}, year = {2018}, abstract = {Cosmic-ray electrons and positrons (CREs) at GeV-TeV energies are a unique probe of our local Galactic neighborhood. CREs lose energy rapidly via synchrotron radiation and inverse-Compton scattering processes while propagating within the Galaxy, and these losses limit their propagation distance. For electrons with TeV energies, the limit is on the order of a kiloparsec. Within that distance, there are only a few known astrophysical objects capable of accelerating electrons to such high energies. It is also possible that the CREs are the products of the annihilation or decay of heavy dark matter (DM) particles. VERITAS, an array of imaging air Cherenkov telescopes in southern Arizona, is primarily utilized for gamma-ray astronomy but also simultaneously collects CREs during all observations. We describe our methods of identifying CREs in VERITAS data and present an energy spectrum, extending from 300 GeV to 5 TeV, obtained from approximately 300 hours of observations. A single power-law fit is ruled out in VERITAS data. We find that the spectrum of CREs is consistent with a broken power law, with a break energy at 710 +/- 40(stat) +/- 140(syst) GeV.}, language = {en} } @article{AbeysekaraArcherBenbowetal.2018, author = {Abeysekara, A. U. and Archer, A. and Benbow, Wystan and Bird, Ralph and Brose, Robert and Buchovecky, M. and Buckley, J. H. and Bugaev, V. and Chromey, A. J. and Connolly, M. P. and Cui, Wei and Daniel, M. K. and Falcone, A. and Feng, Qi and Finley, John P. and Fortson, L. and Furniss, Amy and Huetten, M. 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 Kertzman, M. and Kieda, David and Krause, M. and Krennrich, F. and Kumar, S. and Lang, M. J. and Lin, T. T. Y. and McArthur, S. and Moriarty, P. and Mukherjee, Reshmi and Ong, R. A. and Otte, Adam Nepomuk and Park, Nahee 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 Sembroski, G. H. and Shahinyan, Karlen and Sushch, I. 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 Abdollahi, S. and Ajello, Marco and Baldini, Luca and Barbiellini, G. and Bastieri, Denis and Bellazzini, Ronaldo and Berenji, B. and Bissaldi, Elisabetta and Blandford, R. D. and Bonino, R. and Bottacini, E. and Brandt, Terri J. and Bruel, P. and Buehler, R. and Cameron, R. A. and Caputo, R. and Caraveo, P. A. and Castro, D. and Cavazzuti, E. and Charles, Eric and Chiaro, G. and Ciprini, S. and Cohen-Tanugi, Johann and Costantin, D. and Cutini, S. and de Palma, F. and Di Lalla, N. and Di Mauro, M. and Di Venere, L. and Dominguez, A. and Favuzzi, C. and Fegan, S. J. and Franckowiak, Anna and Fukazawa, Yasushi and Funk, Stefan and Fusco, Piergiorgio and Gargano, Fabio and Gasparrini, Dario and Giglietto, Nicola and Giordano, F. and Giroletti, Marcello and Green, D. and Grenier, I. A. and Guillemot, L. and Guiriec, Sylvain and Hays, Elizabeth and Hewitt, John W. and Horan, D. and Johannesson, G. and Kensei, S. and Kuss, M. and Larsson, Stefan and Latronico, L. and Lemoine-Goumard, Marianne and Li, J. and Longo, Francesco and Loparco, Francesco and Lovellette, M. N. and Lubrano, Pasquale and Magill, Jeffrey D. and Maldera, Simone and Mazziotta, Mario Nicola and McEnery, J. E. and Michelson, P. F. and Mitthumsiri, W. and Mizuno, Tsunefumi and Monzani, Maria Elena and Morselli, Aldo and Moskalenko, Igor V. and Negro, M. and Nuss, E. and Ojha, R. and Omodei, Nicola and Orienti, M. and Orlando, E. and Palatiello, M. and Paliya, Vaidehi S. and Paneque, D. and Perkins, Jeremy S. and Persic, M. and Pesce-Rollins, Melissa and Petrosian, Vahe' and Piron, F. and Porter, Troy A. and Principe, G. and Raino, S. and Rando, Riccardo and Rani, B. and Razzano, Massimilano and Razzaque, Soebur and Reimer, A. and Reimer, Olaf and Reposeur, T. and Sgro, C. and Siskind, E. J. and Spandre, Gloria and Spinelli, P. and Suson, D. J. and Tajima, Hiroyasu and Thayer, J. B. and Thompson, David J. and Torres, Diego F. and Tosti, Gino and Troja, Eleonora and Valverde, J. and Vianello, Giacomo and Vogel, M. and Wood, K. and Yassine, M. and Alfaro, R. and Alvarez, C. and Alvarez, J. D. and Arceo, R. and Arteaga-Velazquez, J. C. and Rojas, D. Avila and Ayala Solares, H. A. and Becerril, A. and Belmont-Moreno, E. and BenZvi, S. Y. and Bernal, A. and Braun, J. and Brisbois, C. and Caballero-Mora, K. S. and Capistran, T. and Carraminana, A. and Casanova, Sabrina and Castillo, M. and Cotti, U. and Cotzomi, J. and Coutino de Leon, S. and De Leon, C. and De la Fuente, E. and Dichiara, S. and Dingus, B. L. and DuVernois, M. A. and Diaz-Velez, J. C. and Engel, K. and Enriquez-Rivera, O. and Fiorino, D. W. and Fleischhack, H. and Fraija, N. and Garcia-Gonzalez, J. A. and Garfias, F. and Gonzalez Munoz, A. and Gonzalez, M. M. and Goodman, J. A. and Hampel-Arias, Z. and Harding, J. P. and Hernandez, S. and Hernandez-Almada, A. and Hona, B. and Hueyotl-Zahuantitla, F. and Hui, C. M. and Huntemeyer, P. and Iriarte, A. and Jardin-Blicq, A. and Joshi, V. and Kaufmann, S. and Lara, A. and Lauer, R. J. and Lee, W. H. and Lennarz, D. and Leon Vargas, H. and Linnemann, J. T. and Longinotti, A. L. and Luis-Raya, G. and Luna-Garcia, R. and Lopez-Coto, R. and Malone, K. and Marinelli, S. S. and Martinez, O. and Martinez-Castellanos, I. and Martinez-Castro, J. and Martinez-Huerta, H. and Matthews, J. A. and Miranda-Romagnoli, P. and Moreno, E. and Mostafa, M. and Nayerhoda, A. and Nellen, L. and Newbold, M. and Nisa, M. U. and Noriega-Papaqui, R. and Pelayo, R. and Pretz, J. and Perez-Perez, E. G. and Ren, Z. and Rho, C. D. and Riviere, C. and Rosa-Gonzalez, D. and Rosenberg, M. and Ruiz-Velasco, E. and Salazar, H. and Greus, F. Salesa and Sandoval, A. and Schneider, M. and Arroyo, M. Seglar and Sinnis, G. and Smith, A. J. and Springer, R. W. and Surajbali, P. and Taboada, Ignacio and Tibolla, O. and Tollefson, K. and Torres, I. and Ukwatta, Tilan N. and Villasenor, L. and Weisgarber, T. and Westerhoff, Stefan and Wisher, I. G. and Wood, J. and Yapici, Tolga and Yodh, G. and Zepeda, A. and Zhou, H.}, title = {VERITAS and Fermi-LAT Observations of TeV Gamma-Ray Sources Discovered by HAWC in the 2HWC Catalog}, series = {The astrophysical journal : an international review of spectroscopy and astronomical physics}, volume = {866}, journal = {The astrophysical journal : an international review of spectroscopy and astronomical physics}, number = {1}, publisher = {IOP Publ. Ltd.}, address = {Bristol}, organization = {VERITAS Collaboration Fermi-LAT Collaboration HAWC Collaboration}, issn = {0004-637X}, doi = {10.3847/1538-4357/aade4e}, pages = {18}, year = {2018}, abstract = {The High Altitude Water Cherenkov (HAWC) collaboration recently published their 2HWC catalog, listing 39 very high energy (VHE; >100 GeV) gamma-ray sources based on 507 days of observation. Among these, 19 sources are not associated with previously known teraelectronvolt (TeV) gamma-ray sources. We have studied 14 of these sources without known counterparts with VERITAS and Fermi-LAT. VERITAS detected weak gamma-ray emission in the 1 TeV-30 TeV band in the region of DA 495, a pulsar wind nebula coinciding with 2HWC J1953+294, confirming the discovery of the source by HAWC. We did not find any counterpart for the selected 14 new HAWC sources from our analysis of Fermi-LAT data for energies higher than 10 GeV. During the search, we detected gigaelectronvolt (GeV) gamma-ray emission coincident with a known TeV pulsar wind nebula, SNR G54.1+0.3 (VER J1930+188), and a 2HWC source, 2HWC J1930+188. The fluxes for isolated, steady sources in the 2HWC catalog are generally in good agreement with those measured by imaging atmospheric Cherenkov telescopes. However, the VERITAS fluxes for SNR G54.1+0.3, DA 495, and TeV J2032+4130 are lower than those measured by HAWC, and several new HAWC sources are not detected by VERITAS. This is likely due to a change in spectral shape, source extension, or the influence of diffuse emission in the source region.}, language = {en} } @article{BenbowBirdBrilletal.2019, author = {Benbow, W. and Bird, R. and Brill, A. and Brose, Robert and Chromey, A. J. and Daniel, M. K. and Feng, Q. and Finley, J. P. and Fortson, L. and Furniss, A. and Gillanders, G. H. and Giuri, C. and Gueta, O. and Hanna, D. and Halpern, J. P. and Hassan, Tarek and Holder, J. and Hughes, G. and Humensky, T. B. and Joyce, Amy M. and Kaaret, P. and Kar, P. and Kelley-Hoskins, N. and Kertzman, M. and Kieda, D. and Krause, M. and Lang, M. J. and Lin, T. T. Y. and Maier, Gernot and Matthews, N. and Moriarty, P. and Mukherjee, R. and Nieto, D. and Nievas-Rosillos, M. and Ong, R. A. and Park, N. and Petrashyk, A. and Pohl, Martin and Pueschel, Elisa and Quinn, John and Ragan, K. and Reynolds, P. T. and Richards, G. T. and Roache, E. and Rulten, C. and Sadeh, Iftach and Santander, M. and Sembroski, G. H. and Shahinyan, K. and Sushch, Iurii and Wakely, S. P. and Wells, R. M. and Wilcox, P. and Wilhelm, Alina and Williams, David A. and Williamson, T. J.}, title = {Direct measurement of stellar angular diameters by the VERITAS Cherenkov telescopes}, series = {Nature astronomy}, volume = {3}, journal = {Nature astronomy}, number = {6}, publisher = {Nature Publ. Group}, address = {London}, issn = {2397-3366}, doi = {10.1038/s41550-019-0741-z}, pages = {511 -- 516}, year = {2019}, abstract = {The angular size of a star is a critical factor in determining its basic properties1. Direct measurement of stellar angular diameters is difficult: at interstellar distances stars are generally too small to resolve by any individual imaging telescope. This fundamental limitation can be overcome by studying the diffraction pattern in the shadow cast when an asteroid occults a star2, but only when the photometric uncertainty is smaller than the noise added by atmospheric scintillation3. Atmospheric Cherenkov telescopes used for particle astrophysics observations have not generally been exploited for optical astronomy due to the modest optical quality of the mirror surface. However, their large mirror area makes them well suited for such high-time-resolution precision photometry measurements4. Here we report two occultations of stars observed by the Very Energetic Radiation Imaging Telescope Array System (VERITAS)5 Cherenkov telescopes with millisecond sampling, from which we are able to provide a direct measurement of the occulted stars' angular diameter at the ≤0.1 mas scale. This is a resolution never achieved before with optical measurements and represents an order of magnitude improvement over the equivalent lunar occultation method6. We compare the resulting stellar radius with empirically derived estimates from temperature and brightness measurements, confirming the latter can be biased for stars with ambiguous stellar classifications.}, language = {en} } @article{AhnenAnsoldiAntonellietal.2018, author = {Ahnen, M. L. and Ansoldi, S. and Antonelli, L. A. and Arcaro, C. and Babic, A. and Banerjee, B. and Bangale, P. and Barres de Almeida, U. and Barrio, J. A. and Gonzalez, J. Becerra and Bednarek, W. and Bernardini, E. and Berti, A. and Bhattacharyya, W. and Blanch, O. and Bonnoli, G. and Carosi, R. and Carosi, A. and Chatterjee, A. and Colak, S. M. and Colin, P. and Colombo, E. and Contreras, J. L. and Cortina, J. and Covino, S. and Cumani, P. and Da Vela, P. and Dazzi, F. and De Angelis, A. and De Lotto, B. and Delfino, M. and Delgado, Jose Miguel Martins and Di Pierro, F. and Doert, M. and Dominguez, A. and Prester, D. Dominis and Doro, M. and Glawion, D. Eisenacher and Engelkemeier, M. and Ramazani, V. Fallah and Fernandez-Barral, A. and Fidalgo, D. and Fonseca, M. V. and Font, L. and Fruck, C. and Galindo, D. and Lopez, R. J. Garcia and Garczarczyk, M. and Gaug, M. and Giammaria, P. and Godinovic, N. and Gora, D. and Guberman, D. and Hadasch, D. and Hahn, A. and Hassan, T. and Hayashida, M. and Herrera, J. and Hose, J. and Hrupec, D. and Ishio, K. and Konno, Y. and Kubo, H. and Kushida, J. and Kuvezdic, D. and Lelas, D. and Lindfors, E. and Lombardi, S. and Longo, F. and Lopez, M. and Maggio, C. and Majumdar, P. and Makariev, M. and Maneva, G. and Manganaro, M. and Maraschi, L. and Mariotti, M. and Martinez, M. and Mazin, D. and Menzel, U. and Minev, M. and Miranda, J. M. and Mirzoyan, R. and Moralejo, A. and Moreno, V. and Moretti, E. and Nagayoshi, T. and Neustroev, V. and Niedzwiecki, A. and Nievas Rosillo, M. and Nigro, C. and Nilsson, K. and Ninci, D. and Nishijima, K. and Noda, K. and Nogues, L. and Paiano, S. and Palacio, J. and Paneque, D. and Paoletti, R. and Paredes, J. M. and Pedaletti, G. and Peresano, M. and Perri, L. and Persic, M. and Moroni, P. G. Prada and Prandini, E. and Puljak, I. and Garcia, J. R. and Reichardt, I. and Ribo, M. and Rico, J. and Righi, C. and Rugliancich, A. and Saito, T. and Satalecka, K. and Schroeder, S. and Schweizer, T. and Shore, S. N. and Sitarek, J. and Snidaric, I. and Sobczynska, D. and Stamerra, A. and Strzys, M. and Suric, T. and Takalo, L. and Tavecchio, F. and Temnikov, P. and Terzic, T. and Teshima, M. and Torres-Alba, N. and Treves, A. and Tsujimoto, S. and Vanzo, G. and Vazquez Acosta, M. and Vovk, I. and Ward, J. E. and Will, M. and Zaric, D. and Arbet-Engels, A. and Baack, D. and Balbo, M. and Biland, A. and Blank, M. and Bretz, T. and Bruegge, K. and Bulinski, M. and Buss, J. and Dmytriiev, A. and Dorner, D. and Einecke, S. and Elsaesser, D. and Herbst, T. and Hildebrand, D. and Kortmann, L. and Linhoff, L. and Mahlke, M. and Mannheim, K. and Mueller, S. A. and Neise, D. and Neronov, A. and Noethe, M. and Oberkirch, J. and Paravac, A. and Rhode, W. and Schleicher, B. and Schulz, F. and Sedlaczek, K. and Shukla, A. and Sliusar, V. and Walter, R. and Archer, A. and Benbow, W. and Bird, R. and Brose, Robert and Buckley, J. H. and Bugaev, V. and Christiansen, J. L. and Cui, W. and Daniel, M. K. and Falcone, A. and Feng, Q. and Finley, J. P. and Gillanders, G. H. and Gueta, O. and Hanna, D. and Hervet, O. and Holder, J. and Hughes, G. and Huetten, M. and Humensky, T. B. and Johnson, C. A. and Kaaret, P. and Kar, P. and Kelley-Hoskins, N. and Kertzman, M. and Kieda, D. and Krause, M. and Krennrich, F. and Kumar, S. and Lang, M. J. and Lin, T. T. Y. and Maier, G. and McArthur, S. and Moriarty, P. and Mukherjee, R. and Ong, R. A. and Otte, A. N. and Park, N. and Petrashyk, A. and Pichel, A. and Pohl, Martin and Quinn, J. and Ragan, K. and Reynolds, P. T. and Richards, G. T. and Roache, E. and Rovero, A. C. and Rulten, C. and Sadeh, I. and Santander, M. and Sembroski, G. H. and Shahinyan, K. and Sushch, Iurii and Tyler, J. and Wakely, S. P. and Weinstein, A. and Wells, R. M. and Wilcox, P. and Wilhel, A. and Williams, D. A. and Williamson, T. J. and Zitzer, B. and Perri, M. and Verrecchia, F. and Leto, C. and Villata, M. and Raiteri, C. M. and Jorstad, S. G. and Larionov, V. M. and Blinov, D. A. and Grishina, T. S. and Kopatskaya, E. N. and Larionova, E. G. and Nikiforova, A. A. and Morozova, D. A. and Troitskaya, Yu. V. and Troitsky, I. S. and Kurtanidze, O. M. and Nikolashvili, M. G. and Kurtanidze, S. O. and Kimeridze, G. N. and Chigladze, R. A. and Strigachev, A. and Sadun, A. C.}, title = {Extreme HBL behavior of Markarian 501 during 2012}, series = {Astronomy and astrophysics : an international weekly journal / European Southern Observatory (ESO)}, volume = {620}, journal = {Astronomy and astrophysics : an international weekly journal / European Southern Observatory (ESO)}, publisher = {EDP Sciences}, address = {Les Ulis}, organization = {MAGIC Collaboration FACT Collaboration VERITAS Collaboration}, issn = {1432-0746}, doi = {10.1051/0004-6361/201833704}, pages = {23}, year = {2018}, abstract = {Aims. We aim to characterize the multiwavelength emission from Markarian 501 (Mrk 501), quantify the energy-dependent variability, study the potential multiband correlations, and describe the temporal evolution of the broadband emission within leptonic theoretical scenarios. Methods. We organized a multiwavelength campaign to take place between March and July of 2012. Excellent temporal coverage was obtained with more than 25 instruments, including the MAGIC, FACT and VERITAS Cherenkov telescopes, the instruments on board the Swift and Fermi spacecraft, and the telescopes operated by the GASP-WEBT collaboration. Results. Mrk 501 showed a very high energy (VHE) gamma-ray flux above 0.2 TeV of similar to 0.5 times the Crab Nebula flux (CU) for most of the campaign. The highest activity occurred on 2012 June 9, when the VHE flux was similar to 3 CU, and the peak of the high-energy spectral component was found to be at similar to 2 TeV. Both the X-ray and VHE gamma-ray spectral slopes were measured to be extremely hard, with spectral indices <2 during most of the observing campaign, regardless of the X-ray and VHE flux. This study reports the hardest Mrk 501 VHE spectra measured to date. The fractional variability was found to increase with energy, with the highest variability occurring at VHE. Using the complete data set, we found correlation between the X-ray and VHE bands; however, if the June 9 flare is excluded, the correlation disappears (significance <3 sigma) despite the existence of substantial variability in the X-ray and VHE bands throughout the campaign. Conclusions. The unprecedentedly hard X-ray and VHE spectra measured imply that their low- and high-energy components peaked above 5 keV and 0.5 TeV, respectively, during a large fraction of the observing campaign, and hence that Mrk 501 behaved like an extreme high-frequency-peaked blazar (EHBL) throughout the 2012 observing season. This suggests that being an EHBL may not be a permanent characteristic of a blazar, but rather a state which may change over time. The data set acquired shows that the broadband spectral energy distribution (SED) of Mrk 501, and its transient evolution, is very complex, requiring, within the framework of synchrotron self-Compton (SSC) models, various emission regions for a satisfactory description. Nevertheless the one-zone SSC scenario can successfully describe the segments of the SED where most energy is emitted, with a significant correlation between the electron energy density and the VHE gamma-ray activity, suggesting that most of the variability may be explained by the injection of high-energy electrons. The one-zone SSC scenario used reproduces the behavior seen between the measured X-ray and VHE gamma-ray fluxes, and predicts that the correlation becomes stronger with increasing energy of the X-rays.}, language = {en} } @article{AllenArchambaultArcheretal.2017, author = {Allen, C. and Archambault, S. and Archer, A. and Benbow, W. and Bird, R. and Bourbeau, E. and Brose, Robert and Buchovecky, M. and Buckley, J. H. and Bugaev, V. and Cardenzana, J. V. and Cerruti, M. and Chen, Xuhui and Christiansen, J. L. and Connolly, M. P. and Cui, W. and Daniel, M. K. and Eisch, J. D. and Falcone, Abe and Feng, Q. and Fernandez-Alonso, M. and Finley, J. P. and Fleischhack, H. and Flinders, A. and Fortson, L. and Furniss, A. and Gillanders, G. H. and Griffin, S. and Grube, J. and Huetten, M. and Hakansson, N. and Hanna, D. and Hervet, O. and Holder, J. and Hughes, G. 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 Petrashyk, A. 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 Rulten, C. and Sadeh, I. and Santander, Marcos and Sembroski, G. H. and Shahinyan, K. and Telezhinsky, Igor O. and Tucci, J. V. and Tyler, J. and Wakely, S. P. and Weinstein, A. and Wilhelm, Alina and Williams, D. A.}, title = {Very-High-Energy gamma-Ray Observations of the Blazar 1ES 2344+514 with VERITAS}, series = {Monthly notices of the Royal Astronomical Society}, volume = {471}, journal = {Monthly notices of the Royal Astronomical Society}, publisher = {Oxford Univ. Press}, address = {Oxford}, issn = {0035-8711}, doi = {10.1093/mnras/stx1756}, pages = {2117 -- 2123}, year = {2017}, abstract = {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.}, language = {en} } @article{AbeysekaraArchambaultArcheretal.2017, author = {Abeysekara, A. U. and Archambault, S. and Archer, A. and Benbow, W. and Bird, R. and Brose, Robert and Buchovecky, M. and Buckley, J. H. and Bugaev, V. and Cerruti, M. and Connolly, M. P. and Cui, W. and Falcone, A. and Feng, Q. and Finley, J. P. and Fleischhack, H. and Fortson, L. and Furniss, A. and Gillanders, G. H. and Griffin, S. and Grube, J. and Huetten, M. and Hanna, D. and Hervet, O. 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 Moriarty, P. and Mukherjee, R. and Nieto, D. and Ong, R. A. and Otte, A. N. and Park, N. and Petrashyk, 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 Rulten, C. and Sadeh, I. and Santander, M. and Sembroski, G. H. and Shahinyan, K. and Staszak, D. and Telezhinsky, Igor O. and Tyler, J. and Vassiliev, V. V. and Wakely, S. P. and Weiner, O. M. and Weinstein, A. and Wilcox, P. and Wilhelm, Alina and Williams, D. A. and Zitzer, B.}, title = {Discovery of Very-high-energy Emission from RGB J2243+203 and Derivation of Its Redshift Upper Limit}, series = {The astrophysical journal : an international review of spectroscopy and astronomical physics ; Supplement series}, volume = {233}, journal = {The astrophysical journal : an international review of spectroscopy and astronomical physics ; Supplement series}, publisher = {IOP Publ. Ltd.}, address = {Bristol}, issn = {0067-0049}, doi = {10.3847/1538-4365/aa8d76}, pages = {1188 -- 1204}, year = {2017}, abstract = {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.}, 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{AbeysekaraArchambaultArcheretal.2016, author = {Abeysekara, A. U. 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 Christiansen, J. L. 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 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 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 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 Pelassa, V. and Petrashyk, A. and Petry, D. and Pohl, Martin and Popkow, A. and Pueschel, Elisa and Quinn, J. and Ragan, K. and Ratliff, G. and Reyes, L. C. and Reynolds, P. T. and Reynolds, K. 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 Vincent, S. and Wakely, S. P. and Weiner, O. M. and Weinstein, A. and Wilhelm, Alina and Williams, D. A. and Zitzer, B.}, title = {VERITAS and multiwavelength observations of the BL Lacertae object 1ES 1741+196}, series = {Monthly notices of the Royal Astronomical Society}, volume = {459}, journal = {Monthly notices of the Royal Astronomical Society}, publisher = {Oxford Univ. Press}, address = {Oxford}, issn = {0035-8711}, doi = {10.1093/mnras/stw664}, pages = {2550 -- 2557}, year = {2016}, abstract = {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.}, 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} } @unpublished{AcharyaActisAghajanietal.2013, author = {Acharya, B. S. and Actis, M. and Aghajani, T. and Agnetta, G. and Aguilar, J. and Aharonian, Felix A. and Ajello, M. and Akhperjanian, A. G. and Alcubierre, M. and Aleksic, J. and Alfaro, R. and Aliu, E. and Allafort, A. J. and Allan, D. and Allekotte, I. and Amato, E. and Anderson, J. and Ang{\"u}ner, Ekrem Oǧuzhan and Antonelli, L. A. and Antoranz, P. and Aravantinos, A. and Arlen, T. and Armstrong, T. and Arnaldi, H. and Arrabito, L. and Asano, K. and Ashton, T. and Asorey, H. G. and Awane, Y. and Baba, H. and Babic, A. and Baby, N. and Baehr, J. and Bais, A. and Baixeras, C. and Bajtlik, S. and Balbo, M. and Balis, D. and Balkowski, C. and Bamba, A. and Bandiera, R. and Barber, A. and Barbier, C. and Barcelo, M. and Barnacka, Anna and Barnstedt, J{\"u}rgen and Barres de Almeida, U. and Barrio, J. A. and Basili, A. and Basso, S. and Bastieri, D. and Bauer, C. and Baushev, Anton N. and Becerra Gonzalez, J. and Becherini, Yvonne and Bechtol, K. C. and Tjus, J. Becker and Beckmann, Volker and Bednarek, W. and Behera, B. and Belluso, M. and Benbow, W. and Berdugo, J. and Berger, K. and Bernard, F. and Bernardino, T. and Bernl{\"o}hr, K. and Bhat, N. and Bhattacharyya, S. and Bigongiari, C. and Biland, A. and Billotta, S. and Bird, T. and Birsin, E. and Bissaldi, E. and Biteau, Jonathan and Bitossi, M. and Blake, S. and Blanch Bigas, O. and Blasi, P. and Bobkov, A. A. and Boccone, V. and Boettcher, Markus and Bogacz, L. and Bogart, J. and Bogdan, M. and Boisson, Catherine and Boix Gargallo, J. and Bolmont, J. and Bonanno, G. and Bonardi, A. and Bonev, T. and Bonifacio, P. and Bonnoli, G. and Bordas, Pol and Borgland, A. W. and Borkowski, Janett and Bose, R. and Botner, O. and Bottani, A. and Bouchet, L. and Bourgeat, M. and Boutonnet, C. and Bouvier, A. and Brau-Nogue, S. and Braun, I. and Bretz, T. and Briggs, M. S. and Bringmann, T. and Brook, P. and Brun, Pierre and Brunetti, L. and Buanes, T. and Buckley, J. 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F. and Vallania, P. and Vallejo, G. and van Driel, W. and van Eldik, C. and Vandenbrouke, J. and Vanderwalt, J. and Vankov, H. and Vasileiadis, G. and Vassiliev, V. and Veberic, D. and Vegas, I. and Vercellone, S. and Vergani, S. and Veyssiere, C. and Vialle, J. P. and Viana, A. and Videla, M. and Vincent, P. and Vincent, S. and Vink, J. and Vlahakis, N. and Vlahos, L. and Vogler, P. and Vollhardt, A. and von Gunten, H. P. and Vorobiov, S. and Vuerli, C. and Waegebaert, V. and Wagner, R. and Wagner, R. G. and Wagner, S. and Wakely, S. P. and Walter, R. and Walther, T. and Warda, K. and Warwick, R. and Wawer, P. and Wawrzaszek, R. and Webb, N. and Wegner, P. and Weinstein, A. and Weitzel, Q. and Welsing, R. and Werner, M. and Wetteskind, H. and White, R. and Wierzcholska, A. and Wiesand, S. and Wilkinson, M. and Williams, D. A. and Willingale, R. and Winiarski, K. and Wischnewski, R. and Wisniewski, L. and Wood, M. and Woernlein, A. and Xiong, Q. and Yadav, K. K. and Yamamoto, H. and Yamamoto, T. and Yamazaki, R. and Yanagita, S. and Yebras, J. M. and Yelos, D. and Yoshida, A. and Yoshida, T. and Yoshikoshi, T. and Zabalza, V. and Zacharias, M. and Zajczyk, A. and Zanin, R. and Zdziarski, A. and Zech, Alraune and Zhao, A. and Zhou, X. and Zietara, K. and Ziolkowski, J. and Ziolkowski, P. and Zitelli, V. and Zurbach, C. and Zychowski, P.}, title = {Introducing the CTA concept}, series = {Astroparticle physics}, volume = {43}, journal = {Astroparticle physics}, number = {2}, publisher = {Elsevier}, address = {Amsterdam}, organization = {CTA Consortium}, issn = {0927-6505}, doi = {10.1016/j.astropartphys.2013.01.007}, pages = {3 -- 18}, year = {2013}, abstract = {The Cherenkov Telescope Array (CTA) is a new observatory for very high-energy (VHE) gamma rays. CTA has ambitions science goals, for which it is necessary to achieve full-sky coverage, to improve the sensitivity by about an order of magnitude, to span about four decades of energy, from a few tens of GeV to above 100 TeV with enhanced angular and energy resolutions over existing VHE gamma-ray observatories. An international collaboration has formed with more than 1000 members from 27 countries in Europe, Asia, Africa and North and South America. In 2010 the CTA Consortium completed a Design Study and started a three-year Preparatory Phase which leads to production readiness of CTA in 2014. In this paper we introduce the science goals and the concept of CTA, and provide an overview of the project.}, language = {en} }