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Design concepts for the Cherenkov Telescope Array CTA an advanced facility for ground-based high-energy gamma-ray astronomy (2011)

Actis, M. ; Agnetta, G. ; Aharonian, Felix ; Akhperjanian, A. G. ; Aleksic, J. ; Aliu, E. ; Allan, D. ; Allekotte, I. ; Antico, F. ; Antonelli, L. A. ; Antoranz, P. ; Aravantinos, A. ; Arlen, T. ; Arnaldi, H. ; Artmann, S. ; Asano, K. ; Asorey, H. G. ; Baehr, J. ; Bais, A. ; Baixeras, C. ; Bajtlik, S. ; Balis, D. ; Bamba, A. ; Barbier, C. ; Barcelo, M. ; Barnacka, Anna ; Barnstedt, Jürgen ; de Almeida, U. Barres ; Barrio, J. A. ; Basso, S. ; Bastieri, D. ; Bauer, C. ; Becerra Gonzalez, J. ; Becherini, Yvonne ; Bechtol, K. C. ; Becker, J. ; Beckmann, Volker ; Bednarek, W. ; Behera, B. ; Beilicke, M. ; Belluso, M. ; Benallou, M. ; Benbow, W. ; Berdugo, J. ; Berger, K. ; Bernardino, T. ; Bernlöhr, K. ; Biland, A. ; Billotta, S. ; Bird, T. ; Birsin, E. ; Bissaldi, E. ; Blake, S. ; Blanch Bigas, O. ; Bobkov, A. A. ; Bogacz, L. ; Bogdan, M. ; Boisson, Catherine ; Boix Gargallo, J. ; Bolmont, J. ; Bonanno, G. ; Bonardi, A. ; Bonev, T. ; Borkowski, Janett ; Botner, O. ; Bottani, A. ; Bourgeat, M. ; Boutonnet, C. ; Bouvier, A. ; Brau-Nogue, S. ; Braun, I. ; Bretz, T. ; Briggs, M. S. ; Brun, Pierre ; Brunetti, L. ; Buckley, H. ; Bugaev, V. ; Buehler, R. ; Bulik, Tomasz ; Busetto, G. ; Buson, S. ; Byrum, K. ; Cailles, M. ; Cameron, R. A. ; Canestrari, R. ; Cantu, S. ; Carmona, E. ; Carosi, A. ; Carr, John ; Carton, P. H. ; Casiraghi, M. ; Castarede, H. ; Catalano, O. ; Cavazzani, S. ; Cazaux, S. ; Cerruti, B. ; Cerruti, M. ; Chadwick, M. ; Chiang, J. ; Chikawa, M. ; Cieslar, M. ; Ciesielska, M. ; Cillis, A. N. ; Clerc, C. ; Colin, P. ; Colome, J. ; Compin, M. ; Conconi, P. ; Connaughton, V. ; Conrad, Jan ; Contreras, J. L. ; Coppi, P. ; Corlier, M. ; Corona, P. ; Corpace, O. ; Corti, D. ; Cortina, J. ; Costantini, H. ; Cotter, G. ; Courty, B. ; Couturier, S. ; Covino, S. ; Croston, J. ; Cusumano, G. ; Daniel, M. K. ; Dazzi, F. ; Deangelis, A. ; de Cea del Pozo, E. ; Dal Pino, E. M. de Gouveia ; de Jager, O. ; de la Calle Perez, I. ; De La Vega, G. ; De Lotto, B. ; de Naurois, M. ; Wilhelmi, E. de Ona ; de Souza, V. ; Decerprit, B. ; Deil, C. ; Delagnes, E. ; Deleglise, G. ; Delgado, C. ; Dettlaff, T. ; Di Paolo, A. ; Di Pierro, F. ; Diaz, C. ; Dick, J. ; Dickinson, H. ; Digel, S. W. ; Dimitrov, D. ; Disset, G. ; Djannati-Ataï, A. ; Doert, M. ; Domainko, W. ; Dorner, D. ; Doro, M. ; Dournaux, J. -L. ; Dravins, D. ; Drury, L. ; Dubois, F. ; Dubois, R. ; Dubus, G. ; Dufour, C. ; Durand, D. ; Dyks, J. ; Dyrda, M. ; Edy, E. ; Egberts, K. ; Eleftheriadis, C. ; Elles, S. ; Emmanoulopoulos, D. ; Enomoto, R. ; Ernenwein, J. -P. ; Errando, M. ; Etchegoyen, A. ; Falcone, A. D. ; Farakos, K. ; Farnier, C. ; Federici, S. ; Feinstein, F. ; Ferenc, D. ; Fillin-Martino, E. ; Fink, D. ; Finley, C. ; Finley, J. P. ; Firpo, R. ; Florin, D. ; Foehr, C. ; Fokitis, E. ; Font, Ll. ; Fontaine, G. ; Fontana, A. ; Foerster, A. ; Fortson, L. ; Fouque, N. ; Fransson, C. ; Fraser, G. W. ; Fresnillo, L. ; Fruck, C. ; Fujita, Y. ; Fukazawa, Y. ; Funk, S. ; Gaebele, W. ; Gabici, S. ; Gadola, A. ; Galante, N. ; Gallant, Y. ; Garcia, B. ; Garcia Lopez, R. J. ; Garrido, D. ; Garrido, L. ; Gascon, D. ; Gasq, C. ; Gaug, M. ; Gaweda, J. ; Geffroy, N. ; Ghag, C. ; Ghedina, A. ; Ghigo, M. ; Gianakaki, E. ; Giarrusso, S. ; Giavitto, G. ; Giebels, B. ; Giro, E. ; Giubilato, P. ; Glanzman, T. ; Glicenstein, J. -F. ; Gochna, M. ; Golev, V. ; Gomez Berisso, M. ; Gonzalez, A. ; Gonzalez, F. ; Granena, F. ; Graciani, R. ; Granot, J. ; Gredig, R. ; Green, A. ; Greenshaw, T. ; Grimm, O. ; Grube, J. ; Grudzinska, M. ; Grygorczuk, J. ; Guarino, V. ; Guglielmi, L. ; Guilloux, F. ; Gunji, S. ; Gyuk, G. ; Hadasch, D. ; Haefner, D. ; Hagiwara, R. ; Hahn, J. ; Hallgren, A. ; Hara, S. ; Hardcastle, M. J. ; Hassan, T. ; Haubold, T. ; Hauser, M. ; Hayashida, M. ; Heller, R. ; Henri, G. ; Hermann, G. ; Herrero, A. ; Hinton, J. A. ; Hoffmann, D. ; Hofmann, W. ; Hofverberg, P. ; Horns, D. ; Hrupec, D. ; Huan, H. ; Huber, B. ; Huet, J. -M. ; Hughes, G. ; Hultquist, K. ; Humensky, T. B. ; Huppert, J. -F. ; Ibarra, A. ; Illa, J. M. ; Ingjald, J. ; Inoue, S. ; Inoue, Y. ; Ioka, K. ; Jablonski, C. ; Jacholkowska, A. ; Janiak, M. ; Jean, P. ; Jensen, H. ; Jogler, T. ; Jung, I. ; Kaaret, P. ; Kabuki, S. ; Kakuwa, J. ; Kalkuhl, C. ; Kankanyan, R. ; Kapala, M. ; Karastergiou, A. ; Karczewski, M. ; Karkar, S. ; Karlsson, N. ; Kasperek, J. ; Katagiri, H. ; Katarzynski, K. ; Kawanaka, N. ; Kedziora, B. ; Kendziorra, E. ; Khelifi, B. ; Kieda, D. ; Kifune, T. ; Kihm, T. ; Klepser, S. ; Kluzniak, W. ; Knapp, J. ; Knappy, A. R. ; Kneiske, T. ; Knoedlseder, J. ; Koeck, F. ; Kodani, K. ; Kohri, K. ; Kokkotas, K. ; Komin, N. ; Konopelko, A. ; Kosack, K. ; Kossakowski, R. ; Kostka, P. ; Kotula, J. ; Kowal, G. ; Koziol, J. ; Kraehenbuehl, T. ; Krause, J. ; Krawczynski, H. ; Krennrich, F. ; Kretzschmann, A. ; Kubo, H. ; Kudryavtsev, V. A. ; Kushida, J. ; La Barbera, N. ; La Parola, V. ; La Rosa, G. ; Lopez, A. ; Lamanna, G. ; Laporte, P. ; Lavalley, C. ; Le Flour, T. ; Le Padellec, A. ; Lenain, J. -P. ; Lessio, L. ; Lieunard, B. ; Lindfors, E. ; Liolios, A. ; Lohse, T. ; Lombardi, S. ; Lopatin, A. ; Lorenz, E. ; Lubinski, P. ; Luz, O. ; Lyard, E. ; Maccarone, M. C. ; Maccarone, T. ; Maier, G. ; Majumdar, P. ; Maltezos, S. ; Malkiewicz, P. ; Mana, C. ; Manalaysay, A. ; Maneva, G. ; Mangano, A. ; Manigot, P. ; Marin, J. ; Mariotti, M. ; Markoff, S. ; Martinez, G. ; Martinez, M. ; Mastichiadis, A. ; Matsumoto, H. ; Mattiazzo, S. ; Mazin, D. ; McComb, T. J. L. ; McCubbin, N. ; McHardy, I. ; Medina, C. ; Melkumyan, D. ; Mendes, A. ; Mertsch, P. ; Meucci, M. ; Michalowski, J. ; Micolon, P. ; Mineo, T. ; Mirabal, N. ; Mirabel, F. ; Miranda, J. M. ; Mirzoyan, R. ; Mizuno, T. ; Moal, B. ; Moderski, R. ; Molinari, E. ; Monteiro, I. ; Moralejo, A. ; Morello, C. ; Mori, K. ; Motta, G. ; Mottez, F. ; Moulin, E. ; Mukherjee, R. ; Munar, P. ; Muraishi, H. ; Murase, K. ; Murphy, A. Stj. ; Nagataki, S. ; Naito, T. ; Nakamori, T. ; Nakayama, K. ; Naumann, C. L. ; Naumann, D. ; Nayman, P. ; Nedbal, D. ; Niedzwiecki, A. ; Niemiec, J. ; Nikolaidis, A. ; Nishijima, K. ; Nolan, S. J. ; Nowak, N. ; O'Brien, P. T. ; Ochoa, I. ; Ohira, Y. ; Ohishi, M. ; Ohka, H. ; Okumura, A. ; Olivetto, C. ; Ong, R. A. ; Orito, R. ; Orr, M. ; Osborne, J. P. ; Ostrowski, M. ; Otero, L. ; Otte, A. N. ; Ovcharov, E. ; Oya, I. ; Ozieblo, A. ; Paiano, S. ; Pallota, J. ; Panazol, J. L. ; Paneque, D. ; Panter, M. ; Paoletti, R. ; Papyan, G. ; Paredes, J. M. ; Pareschi, G. ; Parsons, R. D. ; Arribas, M. Paz ; Pedaletti, G. ; Pepato, A. ; Persic, M. ; Petrucci, P. O. ; Peyaud, B. ; Piechocki, W. ; Pita, S. ; Pivato, G. ; Platos, L. ; Platzer, R. ; Pogosyan, L. ; Pohl, Martin ; Pojmanski, G. ; Ponz, J. D. ; Potter, W. ; Prandini, E. ; Preece, R. ; Prokoph, H. ; Puehlhofer, G. ; Punch, M. ; Quel, E. ; Quirrenbach, A. ; Rajda, P. ; Rando, R. ; Rataj, M. ; Raue, M. ; Reimann, C. ; Reimann, O. ; Reimer, A. ; Reimer, O. ; Renaud, M. ; Renner, S. ; Reymond, J. -M. ; Rhode, W. ; Ribo, M. ; Ribordy, M. ; Rico, J. ; Rieger, F. ; Ringegni, P. ; Ripken, J. ; Ristori, P. ; Rivoire, S. ; Rob, L. ; Rodriguez, S. ; Roeser, U. ; Romano, P. ; Romero, G. E. ; Rosier-Lees, S. ; Rovero, A. C. ; Roy, F. ; Royer, S. ; Rudak, B. ; Rulten, C. B. ; Ruppel, J. ; Russo, F. ; Ryde, F. ; Sacco, B. ; Saggion, A. ; Sahakian, V. ; Saito, K. ; Saito, T. ; Sakaki, N. ; Salazar, E. ; Salini, A. ; Sanchez, F. ; Sanchez Conde, M. A. ; Santangelo, A. ; Santos, E. M. ; Sanuy, A. ; Sapozhnikov, L. ; Sarkar, S. ; Scalzotto, V. ; Scapin, V. ; Scarcioffolo, M. ; Schanz, T. ; Schlenstedt, S. ; Schlickeiser, R. ; Schmidt, T. ; Schmoll, J. ; Schroedter, M. ; Schultz, C. ; Schultze, J. ; Schulz, A. ; Schwanke, U. ; Schwarzburg, S. ; Schweizer, T. ; Seiradakis, J. ; Selmane, S. ; Seweryn, K. ; Shayduk, M. ; Shellard, R. C. ; Shibata, T. ; Sikora, M. ; Silk, J. ; Sillanpaa, A. ; Sitarek, J. ; Skole, C. ; Smith, N. ; Sobczynska, D. ; Sofo Haro, M. ; Sol, H. ; Spanier, F. ; Spiga, D. ; Spyrou, S. ; Stamatescu, V. ; Stamerra, A. ; Starling, R. L. C. ; Stawarz, L. ; Steenkamp, R. ; Stegmann, C. ; Steiner, S. ; Stergioulas, N. ; Sternberger, R. ; Stinzing, F. ; Stodulski, M. ; Straumann, U. ; Suarez, A. ; Suchenek, M. ; Sugawara, R. ; Sulanke, K. H. ; Sun, S. ; Supanitsky, A. D. ; Sutcliffe, P. ; Szanecki, M. ; Szepieniec, T. ; Szostek, A. ; Szymkowiak, A. ; Tagliaferri, G. ; Tajima, H. ; Takahashi, H. ; Takahashi, K. ; Takalo, L. ; Takami, H. ; Talbot, R. G. ; Tam, P. H. ; Tanaka, M. ; Tanimori, T. ; Tavani, M. ; Tavernet, J. -P. ; Tchernin, C. ; Tejedor, L. A. ; Telezhinsky, I. ; Temnikov, P. ; Tenzer, C. ; Terada, Y. ; Terrier, R. ; Teshima, M. ; Testa, V. ; Tibaldo, L. ; Tibolla, O. ; Tluczykont, M. ; Peixoto, C. J. Todero ; Tokanai, F. ; Tokarz, M. ; Toma, K. ; Torres, D. F. ; Tosti, G. ; Totani, T. ; Toussenel, F. ; Vallania, P. ; Vallejo, G. ; van der Walt, J. ; van Eldik, C. ; Vandenbroucke, J. ; Vankov, H. ; Vasileiadis, G. ; Vassiliev, V. V. ; Vegas, I. ; Venter, L. ; Vercellone, S. ; Veyssiere, C. ; Vialle, J. P. ; Videla, M. ; Vincent, P. ; Vink, J. ; Vlahakis, N. ; Vlahos, L. ; Vogler, P. ; Vollhardt, A. ; Volpe, F. ; Von Gunten, H. P. ; Vorobiov, S. ; Wagner, S. ; Wagner, R. M. ; Wagner, B. ; Wakely, S. P. ; Walter, P. ; Walter, R. ; Warwick, R. ; Wawer, P. ; Wawrzaszek, R. ; Webb, N. ; Wegner, P. ; Weinstein, A. ; Weitzel, Q. ; Welsing, R. ; Wetteskind, H. ; White, R. ; Wierzcholska, A. ; Wilkinson, M. I. ; Williams, D. A. ; Winde, M. ; Wischnewski, R. ; Wisniewski, L. ; Wolczko, A. ; Wood, M. ; Xiong, Q. ; Yamamoto, T. ; Yamaoka, K. ; Yamazaki, R. ; Yanagita, S. ; Yoffo, B. ; Yonetani, M. ; Yoshida, A. ; Yoshida, T. ; Yoshikoshi, T. ; Zabalza, V. ; Zagdanski, A. ; Zajczyk, A. ; Zdziarski, A. ; Zech, A. ; Zietara, K. ; Ziolkowski, P. ; Zitelli, V. ; Zychowski, P.

Ground-based gamma-ray astronomy has had a major breakthrough with the impressive results obtained using systems of imaging atmospheric Cherenkov telescopes. Ground-based gamma-ray astronomy has a huge potential in astrophysics, particle physics and cosmology. CTA is an international initiative to build the next generation instrument, with a factor of 5-10 improvement in sensitivity in the 100 GeV-10 TeV range and the extension to energies well below 100 GeV and above 100 TeV. CTA will consist of two arrays (one in the north, one in the south) for full sky coverage and will be operated as open observatory. The design of CTA is based on currently available technology. This document reports on the status and presents the major design concepts of CTA.

Veritas observations of gamma-ray bursts detected by swift (2011)

Acciari, V. A. ; Aliu, E. ; Arlen, T. ; Aune, T. ; Beilicke, M. ; Benbow, W. ; Bradbury, S. M. ; Buckley, J. H. ; Bugaev, V. ; Byrum, K. ; Cannon, A. ; Cesarini, A. ; Christiansen, J. L. ; Ciupik, L. ; Collins-Hughes, E. ; Connolly, M. P. ; Cui, W. ; Duke, C. ; Errando, M. ; Falcone, A. ; Finley, J. P. ; Finnegan, G. ; Fortson, L. ; Furniss, A. ; Galante, N. ; Gall, D. ; Godambe, S. ; Griffin, S. ; Grube, J. ; Guenette, R. ; Gyuk, G. ; Hanna, D. ; Holder, J. ; Hughes, G. ; Hui, C. M. ; Humensky, T. B. ; Jackson, D. J. ; Kaaret, P. ; Karlsson, N. ; Kertzman, M. ; Kieda, D. ; Krawczynski, H. ; Krennrich, F. ; Lang, M. J. ; Madhavan, A. S. ; Maier, G. ; McArthur, S. ; McCann, A. ; Moriarty, P. ; Newbold, M. D. ; Ong, R. A. ; Orr, M. ; Otte, A. N. ; Park, N. ; Perkins, J. S. ; Pohl, Martin ; Prokoph, H. ; Quinn, J. ; Ragan, K. ; Reyes, L. C. ; Reynolds, P. T. ; Roache, E. ; Rose, H. J. ; Ruppel, J. ; Saxon, D. B. ; Schroedter, M. ; Sembroski, G. H. ; Sentuerk, G. D. ; Smith, A. W. ; Staszak, D. ; Swordy, S. P. ; Tesic, G. ; Theiling, M. ; Thibadeau, S. ; Tsurusaki, K. ; Varlotta, A. ; Vassiliev, V. V. ; Vincent, S. ; Vivier, M. ; Wakely, S. P. ; Ward, J. E. ; Weekes, T. C. ; Weinstein, A. ; Weisgarber, T. ; Williams, D. A. ; Wood, M.

We present the results of 16 Swift-triggered Gamma-ray burst (GRB) follow-up observations taken with the Very Energetic Radiation Imaging Telescope Array System (VERITAS) telescope array from 2007 January to 2009 June. The median energy threshold and response time of these observations were 260 GeV and 320 s, respectively. Observations had an average duration of 90 minutes. Each burst is analyzed independently in two modes: over the whole duration of the observations and again over a shorter timescale determined by the maximum VERITAS sensitivity to a burst with a t(-1.5) time profile. This temporal model is characteristic of GRB afterglows with high-energy, long-lived emission that have been detected by the Large Area Telescope on board the Fermi satellite. No significant very high energy (VHE) gamma-ray emission was detected and upper limits above the VERITAS threshold energy are calculated. The VERITAS upper limits are corrected for gamma-ray extinction by the extragalactic background light and interpreted in the context of the keV emission detected by Swift. For some bursts the VHE emission must have less power than the keV emission, placing constraints on inverse Compton models of VHE emission.

Multiwavelenght observations of the previously unidentified blzar RX J0648.7+1516 (2011)

Aliu, E. ; Aune, T. ; Beilicke, M. ; Benbow, W. ; Boettcher, Markus ; Bouvier, A. ; Bradbury, S. M. ; Buckley, J. H. ; Bugaev, V. ; Cannon, A. ; Cesarini, A. ; Ciupik, L. ; Connolly, M. P. ; Cui, W. ; Decerprit, G. ; Dickherber, R. ; Duke, C. ; Errando, M. ; Falcone, A. ; Feng, Q. ; Finnegan, G. ; Fortson, L. ; Furniss, A. ; Galante, N. ; Gall, D. ; Gillanders, G. H. ; Godambe, S. ; Griffin, S. ; Grube, J. ; Gyuk, G. ; Hanna, D. ; Hivick, B. ; Holder, J. ; Huan, H. ; Hughes, G. ; Hui, C. M. ; Humensky, T. B. ; Kaaret, P. ; Karlsson, N. ; Kertzman, M. ; Kieda, D. ; Krawczynski, H. ; Krennrich, F. ; Maier, G. ; Majumdar, P. ; McArthur, S. ; McCann, A. ; Moriarty, P. ; Mukherjee, R. ; Nelson, T. ; Ong, R. A. ; Orr, M. ; Otte, A. N. ; Park, N. ; Perkins, J. S. ; Pichel, A. ; Pohl, Martin ; Prokoph, H. ; Quinn, J. ; Ragan, K. ; Reyes, L. C. ; Reynolds, P. T. ; Roache, E. ; Rose, H. J. ; Ruppel, J. ; Saxon, D. B. ; Sembroski, G. H. ; Skole, C. ; Smith, A. W. ; Staszak, D. ; Tesic, G. ; Theiling, M. ; Thibadeau, S. ; Tsurusaki, K. ; Tyler, J. ; Varlotta, A. ; Vassiliev, V. V. ; Wakely, S. P. ; Weekes, T. C. ; Weinstein, A. ; Williams, D. A. ; Zitzer, B. ; Ciprini, S. ; Fumagalli, M. ; Kaplan, K. ; Paneque, D. ; Prochaska, J. X.

We report on the VERITAS discovery of very high energy (VHE) gamma-ray emission above 200 GeV from the high-frequency-peaked BL Lac (HBL) object RX J0648.7+1516 (GB J0648+1516), associated with 1FGL J0648.8+1516. The photon spectrum above 200 GeV is fitted by a power law dN/dE = F-0(E/E-0)(-Gamma) with a photon index Gamma of 4.4 +/- 0.8(stat) +/- 0.3(syst) and a flux normalization F-0 of (2.3 +/- 0.5(stat) +/- 1.2(sys)) x 10(-11) TeV-1 cm(-2) s(-1) with E-0 = 300 GeV. No VHE variability is detected during VERITAS observations of RX J0648.7+1516 between 2010 March 4 and April 15. Following the VHE discovery, the optical identification and spectroscopic redshift were obtained using the Shane 3 m Telescope at the Lick Observatory, showing the unidentified object to be a BL Lac type with a redshift of z = 0.179. Broadband multiwavelength observations contemporaneous with the VERITAS exposure period can be used to subclassify the blazar as an HBL object, including data from the MDM observatory, Swift-UVOT, and X-Ray Telescope, and continuous monitoring at photon energies above 1 GeV from the Fermi Large Area Telescope (LAT). We find that in the absence of undetected, high-energy rapid variability, the one-zone synchrotron self-Compton (SSC) model overproduces the high-energy gamma-ray emission measured by the Fermi-LAT over 2.3 years. The spectral energy distribution can be parameterized satisfactorily with an external-Compton or lepto-hadronic model, which have two and six additional free parameters, respectively, compared to the one-zone SSC model.

Detection of pulsed Gamma Rays Above 100 GeV from the Crab Pulsar (2011)

Aliu, E. ; Arlen, T. ; Aune, T. ; Beilicke, M. ; Benbow, W. ; Bouvier, A. ; Bradbury, S. M. ; Buckley, J. H. ; Bugaev, V. ; Byrum, K. ; Cannon, A. ; Cesarini, A. ; Christiansen, J. L. ; Ciupik, L. ; Collins-Hughes, E. ; Connolly, M. P. ; Cui, W. ; Dickherber, R. ; Duke, C. ; Errando, M. ; Falcone, A. ; Finley, J. P. ; Finnegan, G. ; Fortson, L. ; Furniss, A. ; Galante, N. ; Gall, D. ; Gibbs, K. ; Gillanders, G. H. ; Godambe, S. ; Griffin, S. ; Grube, J. ; Guenette, R. ; Gyuk, G. ; Hanna, D. ; Holder, J. ; Huan, H. ; Hughes, G. ; Hui, C. M. ; Humensky, T. B. ; Imran, A. ; Kaaret, P. ; Karlsson, N. ; Kertzman, M. ; Kieda, D. ; Krawczynski, H. ; Krennrich, F. ; Lang, M. J. ; Lyutikov, M. ; Madhavan, A. S. ; Maier, G. ; Majumdar, P. ; McArthur, S. ; McCann, A. ; McCutcheon, M. ; Moriarty, P. ; Mukherjee, R. ; Nunez, P. ; Ong, R. A. ; Orr, M. ; Otte, A. N. ; Park, N. ; Perkins, J. S. ; Pizlo, F. ; Pohl, Martin ; Prokoph, H. ; Quinn, J. ; Ragan, K. ; Reyes, L. C. ; Reynolds, P. T. ; Roache, E. ; Rose, H. J. ; Ruppel, J. ; Saxon, D. B. ; Schroedter, M. ; Sembroski, G. H. ; Sentuerk, G. D. ; Smith, A. W. ; Staszak, D. ; Tesic, G. ; Theiling, M. ; Thibadeau, S. ; Tsurusaki, K. ; Tyler, J. ; Varlotta, A. ; Vassiliev, V. V. ; Vincent, S. ; Vivier, M. ; Wakely, S. P. ; Ward, J. E. ; Weekes, T. C. ; Weinstein, A. ; Weisgarber, T. ; Williams, D. A. ; Zitzer, B.

We report the detection of pulsed gamma rays from the Crab pulsar at energies above 100 giga-electron volts (GeV) with the Very Energetic Radiation Imaging Telescope Array System (VERITAS) array of atmospheric Cherenkov telescopes. The detection cannot be explained on the basis of current pulsar models. The photon spectrum of pulsed emission between 100 mega-electron volts and 400 GeV is described by a broken power law that is statistically preferred over a power law with an exponential cutoff. It is unlikely that the observation can be explained by invoking curvature radiation as the origin of the observed gamma rays above 100 GeV. Our findings require that these gamma rays be produced more than 10 stellar radii from the neutron star.

VERITAS OBSERVATIONS OF THE TeV BINARY LS I+61 degrees 303 DURING 2008-2010 (2011)

Acciari, V. A. ; Aliu, E. ; Arlen, T. ; Aune, T. ; Beilicke, M. ; Benbow, W. ; Bradbury, S. M. ; Buckley, J. H. ; Bugaev, V. ; Byrum, K. ; Cannon, A. ; Cesarini, A. ; Ciupik, L. ; Collins-Hughes, E. ; Connolly, M. P. ; Cui, W. ; Dickherber, R. ; Duke, C. ; Errando, M. ; Falcone, A. ; Finley, J. P. ; Finnegan, G. ; Fortson, L. ; Furniss, A. ; Galante, N. ; Gall, D. ; Gillanders, G. H. ; Godambe, S. ; Griffin, S. ; Grube, J. ; Guenette, R. ; Gyuk, G. ; Hanna, D. ; Holder, J. ; Hughes, G. ; Hui, C. M. ; Humensky, T. B. ; Kaaret, P. ; Karlsson, N. ; Kertzman, M. ; Kieda, D. ; Krawczynski, H. ; Krennrich, F. ; Lang, M. J. ; LeBohec, S. ; Maier, G. ; Majumdar, P. ; McArthur, S. ; McCann, A. ; Moriarty, P. ; Mukherjee, R. ; Ong, R. A. ; Orr, M. ; Otte, A. N. ; Park, N. ; Perkins, J. S. ; Pohl, Martin ; Prokoph, H. ; Quinn, J. ; Ragan, K. ; Reyes, L. C. ; Reynolds, P. T. ; Roache, E. ; Rose, H. J. ; Ruppel, J. ; Saxon, D. B. ; Schroedter, M. ; Sembroski, G. H. ; Senturk, G. D. ; Smith, A. W. ; Staszak, D. ; Tesic, G. ; Theiling, M. ; Thibadeau, S. ; Tsurusaki, K. ; Varlotta, A. ; Vassiliev, V. V. ; Vincent, S. ; Vivier, M. ; Wakely, S. P. ; Ward, J. E. ; Weekes, T. C. ; Weinstein, A. ; Weisgarber, T. ; Williams, D. A. ; Zitzer, B.

We present the results of observations of the TeV binary LS I + 61 degrees 303 with the VERITAS telescope array between 2008 and 2010, at energies above 300 GeV. In the past, both ground-based gamma-ray telescopes VERITAS and MAGIC have reported detections of TeV emission near the apastron phases of the binary orbit. The observations presented here show no strong evidence for TeV emission during these orbital phases; however, during observations taken in late 2010, significant emission was detected from the source close to the phase of superior conjunction (much closer to periastron passage) at a 5.6 standard deviation (5.6 sigma) post-trials significance. In total, between 2008 October and 2010 December a total exposure of 64.5 hr was accumulated with VERITAS on LS I + 61 degrees 303, resulting in an excess at the 3.3 sigma significance level for constant emission over the entire integrated data set. The flux upper limits derived for emission during the previously reliably active TeV phases (i.e., close to apastron) are less than 5% of the Crab Nebula flux in the same energy range. This result stands in apparent contrast to previous observations by both MAGIC and VERITAS which detected the source during these phases at 10% of the Crab Nebula flux. During the two year span of observations, a large amount of X-ray data were also accrued on LS I + 61 degrees 303 by the Swift X-ray Telescope and the Rossi X-ray Timing Explorer Proportional Counter Array. We find no evidence for a correlation between emission in the X-ray and TeV regimes during 20 directly overlapping observations. We also comment on data obtained contemporaneously by the Fermi Large Area Telescope.

Discovery of OF TeV Gamma-Ray emission from tycho's supernova remnant (2011)

Acciari, V. A. ; Aliu, E. ; Arlen, T. ; Aune, T. ; Beilicke, M. ; Benbow, W. ; Bradbury, S. M. ; Buckley, J. H. ; Bugaev, V. ; Byrum, K. ; Cannon, A. ; Cesarini, A. ; Ciupik, L. ; Collins-Hughes, E. ; Cui, W. ; Dickherber, R. ; Duke, C. ; Errando, M. ; Finley, J. P. ; Finnegan, G. ; Fortson, L. ; Furniss, A. ; Galante, N. ; Gall, D. ; Gillanders, G. H. ; Godambe, S. ; Griffin, S. ; Grube, J. ; Guenette, R. ; Gyuk, G. ; Hanna, D. ; Holder, J. ; Hughes, J. P. ; Hui, C. M. ; Humensky, T. B. ; Kaaret, P. ; Karlsson, N. ; Kertzman, M. ; Kieda, D. ; Krawczynski, H. ; Krennrich, F. ; Lang, M. J. ; LeBohec, S. ; Madhavan, A. S. ; Maier, G. ; Majumdar, P. ; McArthur, S. ; McCann, A. ; Moriarty, P. ; Mukherjee, R. ; Ong, R. A. ; Orr, M. ; Otte, A. N. ; Pandel, D. ; Park, N. H. ; Perkins, J. S. ; Pohl, Martin ; Quinn, J. ; Ragan, K. ; Reyes, L. C. ; Reynolds, P. T. ; Roache, E. ; Rose, H. J. ; Saxon, D. B. ; Schroedter, M. ; Sembroski, G. H. ; Senturk, G. Demet ; Slane, P. ; Smith, A. W. ; Tesic, G. ; Theiling, M. ; Thibadeau, S. ; Tsurusaki, K. ; Varlotta, A. ; Vassiliev, V. V. ; Vincent, S. ; Vivier, M. ; Wakely, S. P. ; Ward, J. E. ; Weekes, T. C. ; Weinstein, A. ; Weisgarber, T. ; Williams, D. A. ; Wood, M. ; Zitzer, B.

We report the discovery of TeV gamma-ray emission from the Type Ia supernova remnant (SNR) G120.1+1.4, known as Tycho's SNR. Observations performed in the period 2008-2010 with the VERITAS ground-based gamma-ray observatory reveal weak emission coming from the direction of the remnant, compatible with a point source located at 00(h)25(m)27(s).0, +64 degrees 10'50 '' (J2000). The TeV photon spectrum measured by VERITAS can be described with a power law dN/dE = C(E/3.42 TeV)(-Gamma) with Gamma = 1.95 +/- 0.51(stat) +/- 0.30(sys) and C = (1.55 +/- 0.43(stat) +/- 0.47(sys)) x 10(-14) cm(-2) s(-1) TeV-1. The integral flux above 1 TeV corresponds to similar to 0.9% of the steady Crab Nebula emission above the same energy, making it one of the weakest sources yet detected in TeV gamma rays. We present both leptonic and hadronic models that can describe the data. The lowest magnetic field allowed in these models is similar to 80 mu G, which may be interpreted as evidence for magnetic field amplification.

Long term observations of B2 1215+30 with veritas (2013)

Aliu, E. ; Archambault, S. ; Arlen, T. ; Aune, T. ; Beilicke, M. ; Benbow, W. ; Bird, R. ; Bouvier, A. ; Buckley, J. H. ; Bugaev, V. ; Cesarini, A. ; Ciupik, L. ; Connolly, M. P. ; Cui, W. ; Dumm, J. ; Errando, M. ; Falcone, A. ; Federici, Simone ; Feng, Q. ; Finley, J. P. ; Fortin, P. ; Fortson, L. ; Furniss, A. ; Galante, N. ; Gerard, L. ; Gillanders, G. H. ; Griffin, S. ; Grube, J. ; Gyuk, G. ; Hanna, D. ; Holder, J. ; Hughes, G. ; Humensky, T. B. ; Kaaret, P. ; Kertzman, M. ; Khassen, Y. ; Kieda, D. ; Krawczynski, H. ; Krennrich, F. ; Lang, M. J. ; Madhavan, A. S. ; Maier, G. ; Majumdar, P. ; McArthur, S. ; McCann, A. ; Moriarty, P. ; Mukherjee, R. ; Nieto, D. ; De Bhroithe, A. O'Faolain ; Ong, R. A. ; Orr, M. ; Otte, A. N. ; Park, N. ; Perkins, J. S. ; Pohl, Martin ; Popkow, A. ; Prokoph, H. ; Quinn, J. ; Ragan, K. ; Reyes, L. C. ; Reynolds, P. T. ; Richards, G. T. ; Roache, E. ; Saxon, D. B. ; Sembroski, G. H. ; Skole, C. ; Smith, A. W. ; Soares-Furtado, M. ; Staszak, D. ; Telezhinsky, I. ; Tesic, G. ; Theiling, M. ; Varlotta, A. ; Vassiliev, V. V. ; Vincent, S. ; Wakely, S. P. ; Weekes, T. C. ; Weinstein, A. ; Welsing, R. ; Williams, D. A. ; Zitzer, B. ; Böttcher, Markus ; Fumagalli, M. ; Jadhav, J.

We report on VERITAS observations of the BL Lac object B2 1215+30 between 2008 and 2012. During this period, the source was detected at very high energies (VHEs; E > 100 GeV) by VERITAS with a significance of 8.9s and showed clear variability on timescales larger than months. In 2011, the source was found to be in a relatively bright state and a power-law fit to the differential photon spectrum yields a spectral index of 3.6 +/- 0.4(stat) +/- 0.3(syst) with an integral flux above 200 GeV of (8.0 +/- 0.9(stat) +/- 3.2(syst)) x 10(-12) cm(-2) s(-1). No short term variability could be detected during the bright state in 2011. Multi-wavelength data were obtained contemporaneously with the VERITAS observations in 2011 and cover optical (Super-LOTIS, MDM, Swift/UVOT), X-ray (Swift/XRT), and gamma-ray (Fermi-LAT) frequencies. These were used to construct the spectral energy distribution (SED) of B2 1215+30. A one-zone leptonic model is used to model the blazar emission and the results are compared to those of MAGIC from early 2011 and other VERITAS-detected blazars. The SED can be reproduced well with model parameters typical for VHE-detected BL Lac objects.

Test of models of the cosmic infrared background with multiwavelength observations of the blazar 1ES 1218+30.4 IN 2009 (2014)

Archambault, S. ; Arlen, T. ; Aune, T. ; Beilicke, M. ; Benbow, W. ; Bird, R. ; Boettcher, Markus ; Bouvier, A. ; Buckley, J. H. ; Bugaev, V. ; Ciupik, L. ; Collins-Hughes, E. ; Connolly, M. P. ; Cui, W. ; Dickherber, R. ; Dumm, J. ; Errando, M. ; Falcone, A. ; Federici, Simone ; Feng, Q. ; Finley, J. P. ; Fortson, L. ; Furniss, A. ; Galante, N. ; Gall, D. ; Garson, A. III. ; Gillanders, G. H. ; Griffin, S. ; Grube, J. ; Gusbar, C. ; Gyuk, G. ; Hanna, D. ; Holder, J. ; Hughes, G. ; Kaaret, P. ; Kertzman, M. ; Khassen, Y. ; Kieda, D. ; Krawczynski, H. ; Lamerato, A. ; Lang, M. J. ; Li, K. ; Madhavan, A. S. ; Maier, G. ; Majumdar, P. ; McArthur, S. ; McCann, A. ; Millis, J. ; Moriarty, P. ; Mukherjee, R. ; Nieto, D. ; Ong, R. A. ; Orr, M. ; Otte, A. N. ; Park, N. ; Perkins, J. S. ; Pohl, Martin ; Popkow, A. ; Prokoph, H. ; Quinn, J. ; Ragan, K. ; Reynolds, P. T. ; Richards, G. T. ; Roache, E. ; Roustazadeh, P. ; Saxon, D. B. ; Sembroski, G. H. ; Senturk, G. D. ; Skole, C. ; Staszak, D. ; Telezhinsky, Igor ; Tesic, G. ; Theiling, M. ; Varlotta, A. ; Vassiliev, V. V. ; Vincent, S. ; Wakely, S. P. ; Weinstein, A. ; Welsing, R. ; Williams, D. A. ; Zitzer, B.

We present the results of a multi-wavelength campaign targeting the blazar 1ES 1218+30.4 with observations with the 1.3 m McGraw-Hill optical telescope, the Rossi X-ray Timing Explorer (RXTE), the Fermi Gamma-Ray Space Telescope, and the Very Energetic Radiation Imaging Telescope Array System (VERITAS). The RXTE and VERITAS observations were spread over a 13 day period and revealed clear evidence for flux variability, and a strong X-ray and gamma-ray flare on 2009 February 26 (MJD 54888). The campaign delivered a well-sampled broadband energy spectrum with simultaneous RXTE and VERITAS very high energy (VHE, > 100 GeV) observations, as well as contemporaneous optical and Fermi observations. The 1ES 1218+30.4 broadband energy spectrum-the first with simultaneous X-ray and VHE gamma-ray energy spectra-is of particular interest as the source is located at a high cosmological redshift for a VHE source (z = 0.182), leading to strong absorption of VHE gamma rays by photons from the optical/infrared extragalactic background light (EBL) via gamma VHE +gamma EBL -> e(+) e(-)pair-creation processes. We model the data with a one-zone synchrotron self-Compton (SSC) emission model and with the extragalactic absorption predicted by several recent EBL models. We find that the observations are consistent with the SSC scenario and all the EBL models considered in this work. We discuss observational and theoretical avenues to improve on the EBL constraints.

Veritas observations of the BL LAC OBJECT PG 1553+113 (2015)

Aliu, E. ; Archer, A. ; Aune, T. ; Barnacka, Anna ; Behera, B. ; Beilicke, M. ; Benbow, W. ; Berger, K. ; Bird, R. ; Buckley, J. H. ; Bugaev, V. ; Byrum, K. ; Cardenzana, J. V. ; Cerruti, M. ; Chen, Xuhui ; Ciupik, L. ; Connolly, M. P. ; Cui, Wei ; Dickinson, H. J. ; Dumm, J. ; Eisch, J. D. ; Errando, M. ; Falcone, A. ; Federici, Simone ; Feng, Q. ; Finley, J. P. ; Fortin, P. ; Fortson, L. ; Furniss, A. ; Galante, N. ; Gillanders, G. H. ; Griffin, S. ; Griffiths, S. T. ; Grube, J. ; Gyuk, G. ; Hakansson, Nils ; Hanna, D. ; Holder, J. ; Hughes, G. ; Humensky, T. B. ; Johnson, C. A. ; Kaaret, P. ; Kar, P. ; Kertzman, M. ; Khassen, Y. ; Kieda, D. ; Krawczynski, H. ; Krennrich, F. ; Kumar, S. ; Lang, M. J. ; Madhavan, A. ; McArthur, S. ; McCann, A. ; Meagher, K. ; Millis, J. ; Moriarty, P. ; Nieto, Daniel ; Ong, R. A. ; Orr, M. ; Otte, A. N. ; Park, N. ; Perkins, J. S. ; Pohl, Martin ; Popkow, A. ; Prokoph, H. ; Pueschel, E. ; Quinn, J. ; Ragan, K. ; Rajotte, J. ; Reyes, L. C. ; Reynolds, P. T. ; Richards, G. T. ; Roache, E. ; Sembroski, G. H. ; Shahinyan, K. ; Staszak, D. ; Telezhinsky, I. ; Tucci, J. V. ; Tyler, J. ; Varlotta, A. ; Vassiliev, V. V. ; Wakely, S. P. ; Weinstein, A. ; Welsing, R. ; Wilhelm, Alina ; Williams, D. A. ; Zitzer, B.

We present results from VERITAS observations of the BL Lac object PG 1553+113 spanning the years 2010, 2011, and 2012. The time-averaged spectrum, measured between 160 and 560 GeV, is well described by a power law with a spectral index of 4.33 +/- 0.09. The time-averaged integral flux above 200 GeV measured for this period was (1.69 +/- 0.06) x 10(-11) photons cm(-2) s(-1), corresponding to 6.9% of the Crab Nebula flux. We also present the combined gamma-ray spectrum from the Fermi Large Area Telescope and VERITAS covering an energy range from 100 MeV to 560 GeV. The data are well fit by a power law with an exponential cutoff at 101.9 +/- 3.2 GeV. The origin of the cutoff could be intrinsic to PG 1553+113 or be due to the gamma-ray opacity of our universe through pair production off the extragalactic background light (EBL). Given lower limits to the redshift of z > 0.395 based on optical/UV observations of PG 1553+113, the cutoff would be dominated by EBL absorption. Conversely, the small statistical uncertainties of the VERITAS energy spectrum have allowed us to provide a robust upper limit on the redshift of PG 1553+113 of z <= 0.62. A strongly elevated mean flux of (2.50 +/- 0.14) x10(-11) photons cm(-2) s(-1) (10.3% of the Crab Nebula flux) was observed during 2012, with the daily flux reaching as high as (4.44 +/- 0.71) x10(-11) photons cm(-2) s(-1) (18.3% of the Crab Nebula flux) on MJD 56048. The light curve measured during the 2012 observing season is marginally inconsistent with a steady flux, giving a chi(2) probability for a steady flux of 0.03%.

Rapid TeV Gamma-Ray flaring of bl lacertae (2013)

Arlen, T. ; Aune, T. ; Beilicke, M. ; Benbow, W. ; Bouvier, A. ; Buckley, J. H. ; Bugaev, V. ; Cesarini, A. ; Ciupik, L. ; Connolly, M. P. ; Cui, W. ; Dickherber, R. ; Dumm, J. ; Errando, M. ; Falcone, A. ; Federici, S. ; Feng, Q. ; Finley, J. P. ; Finnegan, G. ; Fortson, L. ; Furniss, A. ; Galante, N. ; Gall, D. ; Griffin, S. ; Grube, J. ; Gyuk, G. ; Hanna, D. ; Holder, J. ; Humensky, T. B. ; Kaaret, P. ; Karlsson, N. ; Kertzman, M. ; Khassen, Y. ; Kieda, D. ; Krawczynski, H. ; Krennrich, F. ; Maier, G. ; Moriarty, P. ; Mukherjee, R. ; Nelson, T. ; de Bhroithe, A. O'Faolain ; Ong, R. A. ; Orr, M. ; Park, N. ; Perkins, J. S. ; Pichel, A. ; Pohl, Martin ; Prokoph, H. ; Quinn, J. ; Ragan, K. ; Reyes, L. C. ; Reynolds, P. T. ; Roache, E. ; Saxon, D. B. ; Schroedter, M. ; Sembroski, G. H. ; Staszak, D. ; Telezhinsky, I. ; Tesic, G. ; Theiling, M. ; Tsurusaki, K. ; Varlotta, A. ; Vincent, S. ; Wakely, S. P. ; Weekes, T. C. ; Weinstein, A. ; Welsing, R. ; Williams, D. A. ; Zitzer, B. ; Jorstad, S. G. ; MacDonald, N. R. ; Marscher, A. P. ; Smith, P. S. ; Walker, R. C. ; Hovatta, T. ; Richards, J. ; Max-Moerbeck, W. ; Readhead, A. ; Lister, M. L. ; Kovalev, Y. Y. ; Pushkarev, A. B. ; Gurwell, M. A. ; Lahteenmaki, A. ; Nieppola, E. ; Tornikoski, M. ; Jarvela, E.

We report on the detection of a very rapid TeV gamma-ray flare from BL Lacertae on 2011 June 28 with the Very Energetic Radiation Imaging Telescope Array System (VERITAS). The flaring activity was observed during a 34.6 minute exposure, when the integral flux above 200 GeV reached (3.4 +/- 0.6) x 10(-6) photons m(-2) s(-1), roughly 125% of the Crab Nebula flux measured by VERITAS. The light curve indicates that the observations missed the rising phase of the flare but covered a significant portion of the decaying phase. The exponential decay time was determined to be 13 +/- 4 minutes, making it one of the most rapid gamma-ray flares seen from a TeV blazar. The gamma-ray spectrum of BL Lacertae during the flare was soft, with a photon index of 3.6 +/- 0.4, which is in agreement with the measurement made previously by MAGIC in a lower flaring state. Contemporaneous radio observations of the source with the Very Long Baseline Array revealed the emergence of a new, superluminal component from the core around the time of the TeV gamma-ray flare, accompanied by changes in the optical polarization angle. Changes in flux also appear to have occurred at optical, UV, and GeV gamma-ray wavelengths at the time of the flare, although they are difficult to quantify precisely due to sparse coverage. A strong flare was seen at radio wavelengths roughly four months later, which might be related to the gamma-ray flaring activities. We discuss the implications of these multiwavelength results.

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