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51. Multiwavelength observations and modeling of 1ES 1959+650 in a low flux state

Author: VERITAS Collaboration, Aliu, E., Archambault, S., Arlen, T., Aune, T., Beilicke, M., Benbow, W., Bird, R., Boettcher, M., Bouvier, A., Bugaev, V., Byrum, K., Cesarini, A., Ciupik, L., Collins-Hughes, E., Connolly, M. P., Cui, W., Dickherber, R., Duke, C., Dumm, J., Errando, M., Falcone, A., Federici, S., Feng, Q., Finley, J. P., Finnegan, G., Fortson, L., Furniss, A., Galante, N., Gall, D., 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., Krennrick, F., Lang, M. J., Madhavan, A. S., Maier, G., Majumdar, P., McArthur, S., McCann, A., Moriarty, P., Mukherjee, R., Nelson, T., de Bhroithe, A. O'Faolain, Ong, R. A., Orr, M., Otte, A. N., Park, N., Perkins, J. S., Pichel, A., Pohl, M., Popkow, A., Prokoph, H., Quinn, J., Ragan, K., Reyes, L. C., Reynolds, P. T., Roache, E., Saxon, D. B., Schroedter, M., Sembroski, G. H., Skole, C., Smith, A. W., Staszak, D., Telezhinsky, I., Theiling, M., Tyler, J., Varlotta, A., Vassiliev, V. V., Wakely, S. P., Weekes, T. C., Weinstein, A., Welsing, R., Williams, D. A., and Zitzer, B.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: We report on the VERITAS observations of the high-frequency peaked BL Lac object 1ES 1959+650 in the period 2007-2011. This source is detected at TeV energies by VERITAS at 16.4 standard deviation (sigma) significance in 7.6 hours of observation in a low flux state. A multiwavelength spectral energy distribution (SED) is constructed from contemporaneous data from VERITAS, Fermi-LAT, RXTE PCA, and Swift UVOT. Swift XRT data is not included in the SED due to a lack of simultaneous observations with VERITAS. In contrast to the orphan gamma-ray flare exhibited by this source in 2002, the X-ray flux of the source is found to vary by an order of magnitude, while other energy regimes exhibit less variable emission. A quasi-equilibrium synchrotron self-Compton model with an additional external radiation field is used to describe three SEDs corresponding to the lowest, highest, and average X-ray states. The variation in the X-ray spectrum is modeled by changing the electron injection spectral index, with minor adjustments of the kinetic luminosity in electrons. This scenario produces small-scale flux variability of order >~2 in the HE (E>1 MeV) and VHE (E>100 GeV) gamma-ray regimes, which is corroborated by the Fermi-LAT, VERITAS, and Whipple 10m telescope light curves., Comment: 9 pages, 7 figures. This is an author-created, un-copyedited version of an article accepted for publication in The Astrophysical Journal. IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from it
Published: 2013
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52. CTA contributions to the 33rd International Cosmic Ray Conference (ICRC2013)

Author: Consortium, The CTA, Abril, O., Acharya, B. S., Actis, M., Agnetta, G., Aguilar, J. A., Aharonian, F., Ajello, M., Akhperjanian, A., Alcubierre, M., Aleksic, J., Alfaro, R., Aliu, E., Allafort, A. J., Allan, D., Allekotte, I., Aloisio, R., Amato, E., Ambrosi, G., Ambrosio, M., Anderson, J., Angüner, E. O., Antonelli, L. A., Antonuccio, V., Antonucci, M., Antoranz, P., Aravantinos, A., Argan, A., Arlen, T., Aramo, C., Armstrong, T., Arnaldi, H., Arrabito, L., Asano, K., Ashton, T., Asorey, H. G., Aune, T., Awane, Y., Baba, H., Babic, A., Baby, N., Bähr, J., Bais, A., Baixeras, C., Bajtlik, S., Balbo, M., Balis, D., Balkowski, C., Ballet, J., Bamba, A., Bandiera, R., Barber, A., Barbier, C., Barceló, M., Barnacka, A., Barnstedt, J., de Almeida, U. Barres, Barrio, J. A., Basili, A., Basso, S., Bastieri, D., Bauer, C., Baushev, A., Becciani, U., Becerra, J., Becherini, Y., Bechtol, K. C., Tjus, J. Becker, Beckmann, V., Bednarek, W., Behera, B., Belluso, M., Benbow, W., Berdugo, J., Berge, D., Berger, K., Bernard, F., Bernardino, T., Bernlöhr, K., Bertucci, B., Bhat, N., Bhattacharyya, S., Biasuzzi, B., Bigongiari, C., Biland, A., Billotta, S., Bird, T., Birsin, E., Bissaldi, E., Biteau, J., Bitossi, M., Blake, S., Bigas, O. Blanch, Blasi, P., Bobkov, A., Boccone, V., Böttcher, M., Bogacz, L., Bogart, J., Bogdan, M., Boisson, C., Gargallo, J. Boix, Bolmont, J., Bonanno, G., Bonardi, A., Bonev, T., Bonifacio, P., Bonnoli, G., Bordas, P., Borgland, A., Borkowski, J., Bose, R., Botner, O., Bottani, A., Bouchet, L., Bourgeat, M., Boutonnet, C., Bouvier, A., Brau-Nogué, S., Braun, I., Bretz, T., Briggs, M., Brigida, M., Bringmann, T., Britto, R., Brook, P., Brun, P., Brunetti, L., Bruno, P., Bucciantini, N., Buanes, T., Buckley, J., Bühler, R., Bugaev, V., Bulgarelli, A., Bulik, T., Busetto, G., Buson, S., Byrum, K., Cailles, M., Cameron, R., Camprecios, J., Canestrari, R., Cantu, S., Capalbi, M., Caraveo, P., Carmona, E., Carosi, A., Carosi, R., Carr, J., Carter, J., Carton, P. -H., Caruso, R., Casanova, S., Cascone, E., Casiraghi, M., Castellina, A., Catalano, O., Cavazzani, S., Cazaux, S., Cerchiara, P., Cerruti, M., Chabanne, E., Chadwick, P., Champion, C., Chaves, R., Cheimets, P., Chen, A., Chiang, J., Chiappetti, L., Chikawa, M., Chitnis, V. R., Chollet, F., Christof, A., Chudoba, J., Cieślar, M., Cillis, A., Cilmo, M., Codino, A., Cohen-Tanugi, J., Colafrancesco, S., Colin, P., Colome, J., Colonges, S., Compin, M., Conconi, P., Conforti, V., Connaughton, V., Conrad, J., Contreras, J. L., Coppi, P., Coridian, J., Corona, P., Corti, D., Cortina, J., Cossio, L., Costa, A., Costantini, H., Cotter, G., Courty, B., Couturier, S., Covino, S., Crimi, G., Criswell, S. J., Croston, J., Cusumano, G., Dafonseca, M., Dale, O., Daniel, M., Darling, J., Davids, I., Dazzi, F., de Angelis, A., De Caprio, V., De Frondat, F., Pino, E. M. de Gouveia Dal, de la Calle, I., De La Vega, G. A., Lopez, R. de los Reyes, de Lotto, B., De Luca, A., de Naurois, M., de Oliveira, Y., Wilhelmi, E. de Oña, de Palma, F., de Souza, V., Decerprit, G., Decock, G., Deil, C., Delagnes, E., Deleglise, G., Delgado, C., della Volpe, D., Demange, P., Depaola, G., Dettlaff, A., Di Girolamo, T., Di Giulio, C., Di Paola, A., Di Pierro, F., di Sciascio, G., Díaz, C., Dick, J., Dickherber, R., Dickinson, H., Diez-Blanco, V., Digel, S., Dimitrov, D., Disset, G., Djannati-Ataï, A., Doert, M., Dohmke, M., Domainko, W., Prester, D. Dominis, Donat, A., Dorner, D., Doro, M., Dournaux, J. -L., Drake, G., Dravins, D., Drury, L., Dubois, F., Dubois, R., Dubus, G., Dufour, C., Dumas, D., Dumm, J., Durand, D., Dwarkadas, V., Dyks, J., Dyrda, M., Ebr, J., Edy, E., Egberts, K., Eger, P., Einecke, S., Eleftheriadis, C., Elles, S., Emmanoulopoulos, D., Engelhaupt, D., Enomoto, R., Ernenwein, J. -P., Errando, M., Etchegoyen, A., Evans, P. A., Falcone, A., Faltenbacher, A., Fantinel, D., Farakos, K., Farnier, C., Farrell, E., Fasola, G., Favill, B. W., Fede, E., Federici, S., Fegan, S., Feinstein, F., Ferenc, D., Ferrando, P., Fesquet, M., Fetfatzis, P., Fiasson, A., Fillin-Martino, E., Fink, D., Finley, C., Finley, J. P., Fiorini, M., Curcoll, R. Firpo, Flandrini, E., Fleischhack, H., Flores, H., Florin, D., Focke, W., Föhr, C., Fokitis, E., Font, L., Fontaine, G., Fornasa, M., Förster, A., Fortson, L., Fouque, N., Franckowiak, A., Franco, F. J., Frankowski, A., Fransson, C., Fraser, G. W., Frei, R., Fresnillo, L., Fruck, C., Fugazza, D., Fujita, Y., Fukazawa, Y., Fukui, Y., Funk, S., Gäbele, W., Gabici, S., Gabriele, R., Gadola, A., Galante, N., Gall, D., Gallant, Y., Gámez-García, J., Garczarczyk, M., García, B., López, R. Garcia, Gardiol, D., Gargano, F., Garrido, D., Garrido, L., Gascon, D., Gaug, M., Gaweda, J., Gebremedhin, L., Geffroy, N., Gerard, L., Ghedina, A., Ghigo, M., Ghislain, P., Giannakaki, E., Gianotti, F., Giarrusso, S., Giavitto, G., Giebels, B., Giglietto, N., Gika, V., Giomi, M., Giommi, P., Giordano, F., Girard, N., Giro, E., Giuliani, A., Glanzman, T., Glicenstein, J. -F., Godinovic, N., Golev, V., Berisso, M. Gomez, Gómez-Ortega, J., Gonzalez, M. M., González, A., González, F., Muñoz, A. González, Gothe, K. S., Grabarczyk, T., Gougerot, M., Graciani, R., Grandi, P., Grañena, F., Granot, J., Grasseau, G., Gredig, R., Green, A., Greenshaw, T., Grégoire, T., Grillo, A., Grimm, O., Grondin, M. -H., Grube, J., Grudzinska, M., Gruev, V., Grünewald, S., Grygorczuk, J., Guarino, V., Gunji, S., Gyuk, G., Hadasch, D., Hagedorn, A., Hagiwara, R., Hahn, J., Hakansson, N., Hallgren, A., Heras, N. Hamer, Hara, S., Hardcastle, M. J., Harezlak, D., Harris, J., Hassan, T., Hatanaka, K., Haubold, T., Haupt, A., Hayakawa, T., Hayashida, M., Heller, R., Henault, F., Henri, G., Hermann, G., Hermel, R., Herrero, A., Hervet, O., Hidaka, N., Hinton, J. A., Hirotani, K., Hoffmann, D., Hofmann, W., Hofverberg, P., Holder, J., Hörandel, J. R., Horns, D., Horville, D., Houles, J., Hrabovsky, M., Hrupec, D., Huan, H., Huber, B., Huet, J. -M., Hughes, G., Humensky, T. B., Huovelin, J., Huppert, J. -F., Ibarra, A., Ikawa, D., Illa, J. M., Impiombato, D., Incorvaia, S., Inoue, S., Inoue, Y., Iocco, F., Ioka, K., Israel, G. L., Jablonski, C., Jacholkowska, A., Jacquemier, J., Jamrozy, M., Janiak, M., Jean, P., Jeanney, C., Jimenez, J. J., Jogler, T., Johnson, C., Johnson, T., Journet, L., Juffroy, C., Jung, I., Kaaret, P., Kabuki, S., Kagaya, M., Kakuwa, J., Kalkuhl, C., Kankanyan, R., Karastergiou, A., Kärcher, K., Karczewski, M., Karkar, S., Kasperek, J., Kastana, D., Katagiri, H., Kataoka, J., Katarzyński, K., Katz, U., Kawanaka, N., Kazanas, D., Kelley-Hoskins, N., Kellner-Leidel, B., Kelly, H., Kendziorra, E., Khélifi, B., Kieda, D. B., Kifune, T., Kihm, T., Kishimoto, T., Kitamoto, K., Kluźniak, W., Knapic, C., Knapp, J., Knödlseder, J., Köck, F., Kocot, J., Kodani, K., Köhne, J. -H., Kohri, K., Kokkotas, K., Kolitzus, D., Komin, N., Kominis, I., Konno, Y., Köppel, H., Korohoda, P., Kosack, K., Koss, G., Kossakowski, R., Koul, R., Kowal, G., Koyama, S., Kozioł, J., Krähenbühl, T., Krause, J., Krawzcynski, H., Krennrich, F., Krepps, A., Kretzschmann, A., Krobot, R., Krueger, P., Kubo, H., Kudryavtsev, V. A., Kushida, J., Kuznetsov, A., La Barbera, A., La Palombara, N., La Parola, V., La Rosa, G., Lacombe, K., Lamanna, G., Lande, J., Languignon, D., Lapington, J. S., Laporte, P., Laurent, B., Lavalley, C., Flour, T. Le, Padellec, A. Le, Lee, S. -H., Lee, W. H., Lefèvre, J. -P., Leich, H., de Oliveira, M. A. Leigui, Lelas, D., Lenain, J. -P., Leoni, R., Leopold, D. J., Lerch, T., Lessio, L., Leto, G., Lieunard, B., Lieunard, S., Lindemann, R., Lindfors, E., Liolios, A., Lipniacka, A., Lockart, H., Lohse, T., Lombardi, S., Longo, F., Lopatin, A., Lopez, M., López-Coto, R., López-Oramas, A., Lorca, A., Lorenz, E., Louis, F., Lubinski, P., Lucarelli, F., Lüdecke, H., Ludwin, J., Luque-Escamilla, P. L., Lustermann, W., Luz, O., Lyard, E., Maccarone, M. C., Maccarone, T. J., Madejski, G. M., Madhavan, A., Mahabir, M., Maier, G., Majumdar, P., Malaguti, G., Malaspina, G., Maltezos, S., Manalaysay, A., Mancilla, A., Mandat, D., Maneva, G., Mangano, A., Manigot, P., Mannheim, K., Manthos, I., Maragos, N., Marcowith, A., Mariotti, M., Marisaldi, M., Markoff, S., Marszałek, A., Martens, C., Martí, J., Martin, J. -M., Martin, P., Martínez, G., Martínez, F., Martínez, M., Massaro, F., Masserot, A., Mastichiadis, A., Mathieu, A., Matsumoto, H., Mattana, F., Mattiazzo, S., Maurer, A., Maurin, G., Maxfield, S., Maya, J., Mazin, D., Comb, L. Mc, McCann, A., McCubbin, N., McHardy, I., McKay, R., Meagher, K., Medina, C., Melioli, C., Melkumyan, D., Melo, D., Mereghetti, S., Mertsch, P., Meucci, M., Meyer, M., Michałowski, J., Micolon, P., Mihailidis, A., Mineo, T., Minuti, M., Mirabal, N., Mirabel, F., Miranda, J. M., Mirzoyan, R., Mistò, A., Mizuno, T., Moal, B., Moderski, R., Mognet, I., Molinari, E., Molinaro, M., Montaruli, T., Monte, C., Monteiro, I., Moore, P., Olaizola, A. Moralejo, Mordalska, M., Morello, C., Mori, K., Morlino, G., Morselli, A., Mottez, F., Moudden, Y., Moulin, E., Mrusek, I., Mukherjee, R., Munar-Adrover, P., Muraishi, H., Murase, K., Murphy, A. StJ., Nagataki, S., Naito, T., Nakajima, D., Nakamori, T., Nakayama, K., Naumann, C., Naumann, D., Naumann-Godo, M., Nayman, P., Nedbal, D., Neise, D., Nellen, L., Neronov, A., Neustroev, V., Neyroud, N., Nicastro, L., Nicolau-Kukliński, J., Niedźwiecki, A., Niemiec, J., Nieto, D., Nikolaidis, A., Nishijima, K., Nishikawa, K. -I., Noda, K., Nolan, S., Northrop, R., Nosek, D., Nowak, N., Nozato, A., Oakes, L., O'Brien, P. T., Ohira, Y., Ohishi, M., Ohm, S., Ohoka, H., Okuda, T., Okumura, A., Olive, J. -F., Ong, R. A., Orito, R., Orr, M., Osborne, J. P., Ostrowski, M., Otero, L. A., Otte, N., Ovcharov, E., Oya, I., Ozieblo, A., Padilla, L., Pagano, I., Paiano, S., Paillot, D., Paizis, A., Palanque, S., Palatka, M., Pallota, J., Palatiello, M., Panagiotidis, K., Panazol, J. -L., Paneque, D., Panter, M., Panzera, M. R., Paoletti, R., Papayannis, A., Papyan, G., Paredes, J. M., Pareschi, G., Parraud, J. -M., Parsons, D., Pauletta, G., Arribas, M. Paz, Pech, M., Pedaletti, G., Pelassa, V., Pelat, D., Perez, M. d. C., Persic, M., Petrucci, P. -O., Peyaud, B., Pichel, A., Pieloth, D., Pierre, E., Pita, S., Pivato, G., Pizzolato, F., Platino, M., Platos, Ł., Platzer, R., Podkladkin, S., Pogosyan, L., Pohl, M., Pojmanski, G., Ponz, J. D., Potter, W., Poutanen, J., Prandini, E., Prast, J., Preece, R., Profeti, F., Prokoph, H., Prouza, M., Proyetti, M., Puerto-Giménez, I., Pühlhofer, G., Puljak, I., Punch, M., Pyzioł, R., Quel, E. J., Quesada, J., Quinn, J., Quirrenbach, A., Racero, E., Rainò, S., Rajda, P. J., Rameez, M., Ramon, P., Rando, R., Rannot, R. C., Rataj, M., Raue, M., Ravignani, D., Reardon, P., Reimann, O., Reimer, A., Reimer, O., Reitberger, K., Renaud, M., Renner, S., Reville, B., Rhode, W., Ribó, M., Ribordy, M., Richards, G., Richer, M. G., Rico, J., Ridky, J., Rieger, F., Ringegni, P., Ripken, J., Ristori, P. R., Rivière, A., Rivoire, S., Rob, L., Rodeghiero, G., Roeser, U., Rohlfs, R., Rojas, G., Romano, P., Romaszkan, W., Romero, G. E., Rosen, S. R., Lees, S. Rosier, Ross, D., Rouaix, G., Rousselle, J., Rousselle, S., Rovero, A. C., Roy, F., Royer, S., Rudak, B., Rulten, C., Rupiński, M., Russo, F., Ryde, F., Saavedra, O., Sacco, B., Saemann, E. O., Saggion, A., Sahakian, V., Saito, K., Saito, T., Saito, Y., Sakaki, N., Sakonaka, R., Salini, A., Sanchez, F., Sanchez-Conde, M., Sandoval, A., Sandaker, H., Sant'Ambrogio, E., Santangelo, A., Santos, E. M., Sanuy, A., Sapozhnikov, L., Sarkar, S., Sartore, N., Sasaki, H., Satalecka, K., Sawada, M., Scalzotto, V., Scapin, V., Scarcioffolo, M., Schafer, J., Schanz, T., Schlenstedt, S., Schlickeiser, R., Schmidt, T., Schmoll, J., Schovanek, P., Schroedter, M., Schubert, A., Schultz, C., Schultze, J., Schulz, A., Schure, K., Schussler, F., Schwab, T., Schwanke, U., Schwarz, J., Schwarzburg, S., Schweizer, T., Schwemmer, S., Schwendicke, U., Schwerdt, C., Segreto, A., Seiradakis, J. -H., Sembroski, G. H., Servillat, M., Seweryn, K., Sharma, M., Shayduk, M., Shellard, R. C., Shi, J., Shibata, T., Shibuya, A., Shore, S., Shum, E., Sideras-Haddad, E., Sidoli, L., Sidz, M., Sieiro, J., Sikora, M., Silk, J., Sillanpää, A., Singh, B. B., Sironi, G., Sitarek, J., Skole, C., Smareglia, R., Smith, A., Smith, D., Smith, J., Smith, N., Sobczyńska, D., Sol, H., Sottile, G., Sowiński, M., Spanier, F., Spiga, D., Spyrou, S., Stamatescu, V., Stamerra, A., Starling, R. L. C., Stawarz, Ł., Steenkamp, R., Stegmann, C., Steiner, S., Stella, C., Stergioulas, N., Sternberger, R., Sterzel, M., Stinzing, F., Stodulski, M., Stolarczyk, Th., Straumann, U., Strazzeri, E., Stringhetti, L., Suarez, A., Suchenek, M., Sugawara, R., Sulanke, K. -H., Sun, S., Supanitsky, A. D., Suric, T., Sutcliffe, P., Sykes, J. M., Szanecki, M., Szepieniec, T., Szostek, A., Tagliaferri, G., Tajima, H., Takahashi, H., Takahashi, K., Takalo, L., Takami, H., Talbot, G., Tammi, J., Tanaka, M., Tanaka, S., Tasan, J., Tavani, M., Tavernet, J. -P., Tejedor, L. A., Telezhinsky, I., Temnikov, P., Tenzer, C., Terada, Y., Terrier, R., Teshima, M., Testa, V., Tezier, D., Thayer, J., Thuermann, D., Tibaldo, L., Tibolla, O., Tiengo, A., Timpanaro, M. C., Tluczykont, M., Peixoto, C. J. Todero, Tokanai, F., Tokarz, M., Toma, K., Tonachini, A., Torii, K., Tornikoski, M., Torres, D. F., Torres, M., Toscano, S., Toso, G., Tosti, G., Totani, T., Toussenel, F., Tovmassian, G., Travnicek, P., Treves, A., Trifoglio, M., Troyano, I., Tsinganos, K., Ueno, H., Umana, G., Umehara, K., Upadhya, S. S., Usher, T., Uslenghi, M., Vagnetti, F., Valdes-Galicia, J. F., Vallania, P., Vallejo, G., van Driel, W., van Eldik, C., Vandenbrouke, J., Vanderwalt, J., Vankov, H., Vasileiadis, G., Vassiliev, V., Veberic, D., Vegas, I., Vercellone, S., Vergani, S., Verzi, V., Vettolani, G. P., Veyssière, C., Vialle, J. P., Viana, A., Videla, M., Vigorito, C., Vincent, P., Vincent, S., Vink, J., Vlahakis, N., Vlahos, L., Vogler, P., Voisin, V., Vollhardt, A., von Gunten, H. -P., Vorobiov, S., Vuerli, C., Waegebaert, V., Wagner, R., Wagner, R. G., Wagner, S., Wakely, S. P., Walter, R., Walther, T., Warda, K., Warwick, R. S., Wawer, P., Wawrzaszek, R., Webb, N., Wegner, P., Weinstein, A., Weitzel, Q., Welsing, R., Werner, M., Wetteskind, H., White, R. J., Wierzcholska, A., Wiesand, S., Wilhelm, A., Wilkinson, M. I., Williams, D. A., Willingale, R., Winde, M., Winiarski, K., Wischnewski, R., Wiśniewski, Ł., Wojcik, P., Wood, M., Wörnlein, A., Xiong, Q., Yadav, K. K., Yamamoto, H., Yamamoto, T., Yamazaki, R., Yanagita, S., Yebras, J. M., Yelos, D., Yoshida, A., Yoshida, T., Yoshikoshi, T., Yu, P., Zabalza, V., Zacharias, M., Zajczyk, A., Zampieri, L., Zanin, R., Zdziarski, A., Zech, A., Zhao, A., Zhou, X., Zietara, K., Ziolkowski, J., Ziółkowski, P., Zitelli, V., Zurbach, C., and Zychowski, P.
Subjects: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Instrumentation and Methods for Astrophysics, High Energy Physics - Experiment
Abstract: Compilation of CTA contributions to the proceedings of the 33rd International Cosmic Ray Conference (ICRC2013), which took place in 2-9 July, 2013, in Rio de Janeiro, Brazil, Comment: Index of CTA conference proceedings at the ICRC2013, Rio de Janeiro (Brazil). v1: placeholder with no arXiv links yet, to be replaced once individual contributions have been all submitted. v2: final with arXiv links to all CTA contributions and full author list
Published: 2013

53. Discovery of TeV Gamma-ray Emission Toward Supernova Remnant SNR G78.2+2.1

Author: Aliu, E., Archambault, S., Arlen, T., Aune, T., Beilicke, M., Benbow, W., Bird, R., Bouvier, A., Bradbury, S. M., Buckley, J. H., Bugaev, V., Byrum, K., Cannon, A., Cesarini, A., Ciupik, L., Collins-Hughes, E., Connolly, M. P., Cui, W., Dickherber, R., Duke, C., Dumm, J., Dwarkadas, V. V., Errando, M., Falcone, A., Federici, S., Feng, Q., Finley, J. P., Finnegan, G., Fortson, L., Furniss, A., Galante, N., Gall, D., Gillanders, G. H., Godambe, S., Gotthelf, E. V., Griffin, S., Grube, J., Gyuk, G., Hanna, D., Holder, J., Huan, H., Hughes, G., Humensky, T. B., Kaaret, P., Karlsson, N., Kertzman, M., Khassen, Y., Kieda, D., Krawczynski, H., Krennrich, F., Lang, M. J., Lee, K., Madhavan, A. S, Maier, G., Majumdar, P., McArthur, S., McCann, A., Millis, J., Moriarty, P., Mukherjee, R., Nelson, T., de Bhróithe, A. O'Faoláin, Ong, R. A., Orr, M., Otte, A. N., Pandel, D., Park, N., Perkins, J. S., Pohl, M., Popkow, A., 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., Şentürk, G. D., Skole, C., Telezhinsky, I., Tešić, G., Theiling, M., Thibadeau, S., Tsurusaki, K., Tyler, J., Varlotta, A., Vassiliev, V. V., Vincent, S., Wakely, S. P., Ward, J. E., Weekes, T. C., Weinstein, A., Weisgarber, T., Welsing, R., Williams, D. A., and Zitzer, B.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: We report the discovery of an unidentified, extended source of very-high-energy (VHE) gamma-ray emission, VER J2019+407, within the radio shell of the supernova remnant SNR G78.2+2.1, using 21.4 hours of data taken by the VERITAS gamma-ray observatory in 2009. These data confirm the preliminary indications of gamma-ray emission previously seen in a two-year (2007-2009) blind survey of the Cygnus region by VERITAS. VER J2019+407, which is detected at a post-trials significance of 7.5 standard deviations in the 2009 data, is localized to the northwestern rim of the remnant in a region of enhanced radio and X-ray emission. It has an intrinsic extent of 0.23^{\circ} \pm 0.03^{\circ} (stat)+0.04^{\circ}_{-0.02}^{\circ}(sys) and its spectrum is well-characterized by a differential power law (dN/dE = N_0 \times (E/TeV)^{-\Gamma}) with a photon index of {\Gamma} = 2.37 \pm 0.14 (stat) \pm 0.20 (sys) and a flux normalization of N0 = 1.5 \pm 0.2 (stat) \pm 0.4(sys) \times 10^-12 ph TeV^{-1} cm^{-2} s^{-1}. This yields an integral flux of 5.2 \pm 0.8 (stat) \pm 1.4 (sys) \times 10^-12 ph cm^{-2} s^{-1} above 320 GeV, corresponding to 3.7% of the Crab Nebula flux. We consider the relationship of the TeV gamma-ray emission with the GeV gamma-ray emission seen from SNR G78.2+2.1 as well as that seen from a nearby cocoon of freshly accelerated cosmic rays. Multiple scenarios are considered as possible origins for the TeV gamma-ray emission, including hadronic particle acceleration at the supernova remnant shock., Comment: 18 pages, 5 figures, accepted for publication in ApJ
Published: 2013
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54. Search for a correlation between very-high-energy gamma rays and giant radio pulses in the Crab pulsar

Author: Aliu, E., Archambault, S., Arlen, T., Aune, T., Beilicke, M., Benbow, W., Bouvier, A., Buckley, J. H., Bugaev, V., Byrum, K., Cesarini, A., Ciupik, L., Collins-Hughes, E., Connolly, M. P., Cui, W., Dickherber, R., Duke, C., Dumm, J., Falcone, A., Federici, S., Feng, Q., Finley, J. P., Finnegan, G., Fortson, L., Furniss, A., Galante, N., Gall, D., Gillanders, G. H., Godambe, S., Griffin, S., Grube, J., Gyuk, G., Hanna, D., Holder, J., Huan, H., Hughes, G., Humensky, T. B., Kaaret, P., Karlsson, N., Khassen, Y., Kieda, D., Krawczynski, H., Krennrich, F., Lang, M. J., LeBohec, S., Lee, K., Lyutikov, M., Madhavan, A. S, Maier, G., Majumdar, P., McArthur, S., McCann, A., Moriarty, P., Mukherjee, R., Nelson, T., de Bhroithe, A. O'Faolain, Ong, R. A., Orr, M., Otte, A. N., Park, N., Perkins, J. S., Pohl, M., Prokoph, H., Quinn, J., Ragan, K., Reyes, L. C., Reynolds, P. T., Roache, E., Saxon, D. B., Schroedter, M., Sembroski, G. H., Senturk, G. D., Smith, A. W., Staszak, D., Telezhinsky, I., Tesic, G., Theiling, M., Thibadeau, S., Tsurusaki, K., Varlotta, A., Vincent, S., Vivier, M., Wagner, R. G., Wakely, S. P., Weekes, T. C., Weinstein, A., Welsing, R., Williams, D. A., Zitzer, B., and Kondratiev, V.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: We present the results of a joint observational campaign between the Green Bank radio telescope and the VERITAS gamma-ray telescope, which searched for a correlation between the emission of very-high-energy (VHE) gamma rays ($E_{\gamma} >$ 150 GeV) and Giant Radio Pulses (GRPs) from the Crab pulsar at 8.9 GHz. A total of 15366 GRPs were recorded during 11.6 hours of simultaneous observations, which were made across four nights in December 2008 and in November and December 2009. We searched for an enhancement of the pulsed gamma-ray emission within time windows placed around the arrival time of the GRP events. In total, 8 different time windows with durations ranging from 0.033 ms to 72 s were positioned at three different locations relative to the GRP to search for enhanced gamma-ray emission which lagged, led, or was concurrent with, the GRP event. Further, we performed separate searches on main pulse GRPs and interpulse GRPs and on the most energetic GRPs in our data sample. No significant enhancement of pulsed VHE emission was found in any of the preformed searches. We set upper limits of 5-10 times the average VHE flux of the Crab pulsar on the flux simultaneous with interpulse GRPs on single-rotation-period time scales. On $\sim$8-second time scales around interpulse GRPs, we set an upper limit of 2-3 times the average VHE flux. Within the framework of recent models for pulsed VHE emission from the Crab pulsar, the expected VHE-GRP emission correlations are below the derived limits., Comment: 12 pages, 12 figures, To appear in The Astrophysical Journal
Published: 2012
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55. Constraints on Cosmic Rays, Magnetic Fields, and Dark Matter from Gamma-Ray Observations of the Coma Cluster of Galaxies with VERITAS and Fermi

Author: Arlen, T., Aune, T., Beilicke, M., Benbow, W., Bouvier, A., Buckley, J. H., Bugaev, V., Byrum, K., Cannon, A., Cesarini, A., Ciupik, L., Collins-Hughes, E., Connolly, M. P., Cui, W., Dickherber, R., Dumm, J., Falcone, A., Federici, S., Feng, Q., Finley, J. P., Finnegan, G., Fortson, L., Furniss, A., Galante, N., Gall, D., Godambe, S., Griffin, S., Grube, J., Gyuk, G., Holder, J., Huan, H., Hughes, G., Humensky, T. B., Imran, A., Kaaret, P., Karlsson, N., Kertzman, M., Khassen, Y., Kieda, D., Krawczynski, H., Krennrich, F., Lee, K., Madhavan, A. S, Maier, G., Majumdar, P., McArthur, S., McCann, A., Moriarty, P., Mukherjee, R., Nelson, T., de Bhróithe, A. O'Faoláin, Ong, R. A., Orr, M., Otte, A. N., Park, N., Perkins, J. S., Pohl, M., Prokoph, H., Quinn, J., Ragan, K., Reyes, L. C., Reynolds, P. T., Roache, E., Ruppel, J., Saxon, D. B., Schroedter, M., Sembroski, G. H., Skole, C., Smith, A. W., Telezhinsky, I., Tešić, G., Theiling, M., Thibadeau, S., Tsurusaki, K., Varlotta, A., Vivier, M., Wakely, S. P., Ward, J. E., Weinstein, A., Welsing, R., Williams, D. A., Zitzer, B., Pfrommer, C., and Pinzke, A.
Subjects: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Cosmology and Nongalactic Astrophysics
Abstract: Observations of radio halos and relics in galaxy clusters indicate efficient electron acceleration. Protons should likewise be accelerated, suggesting that clusters may also be sources of very high-energy (VHE; E>100 GeV) gamma-ray emission. We report here on VHE gamma-ray observations of the Coma galaxy cluster with the VERITAS array of imaging Cherenkov telescopes, with complementing Fermi-LAT observations at GeV energies. No significant gamma-ray emission from the Coma cluster was detected. Integral flux upper limits at the 99% confidence level were measured to be on the order of (2-5)*10^-8\ ph. m^-2 s^-1 (VERITAS, >220 GeV} and ~2*10^-6 ph. m^-2 s^-1 (Fermi, 1-3 GeV), respectively. We use the gamma-ray upper limits to constrain CRs and magnetic fields in Coma. Using an analytical approach, the CR-to-thermal pressure ratio is constrained to be < 16% from VERITAS data and < 1.7% from Fermi data (averaged within the virial radius). These upper limits are starting to constrain the CR physics in self-consistent cosmological cluster simulations and cap the maximum CR acceleration efficiency at structure formation shocks to be <50%. Assuming that the radio-emitting electrons of the Coma halo result from hadronic CR interactions, the observations imply a lower limit on the central magnetic field in Coma of (2 - 5.5) muG, depending on the radial magnetic-field profile and on the gamma-ray spectral index. Since these values are below those inferred by Faraday rotation measurements in Coma (for most of the parameter space), this {renders} the hadronic model a very plausible explanation of the Coma radio halo. Finally, since galaxy clusters are dark-matter (DM) dominated, the VERITAS upper limits have been used to place constraints on the thermally-averaged product of the total self-annihilation cross section and the relative velocity of the DM particles, <\sigma v>. (abr.), Comment: ApJ in press
Published: 2012
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56. VERITAS Observations of the Nova in V407 Cygni

Author: Aliu, E., Archambault, S., Arlen, T., Aune, T., Beilicke, M., Benbow, W., Bouvier, A., Bradbury, S. M., Buckley, J. H., Bugaev, V., Byrum, K., Cannon, A., Cesarini, A., Ciupik, L., Collins-Hughes, E., Connolly, M. P., Cui, W., Decerprit, G., Dickherber, R., Duke, C., Dumm, J., Dwarkadas, V. V., Errando, M., Falcone, A., Feng, Q., Finley, J. P., Finnegan, G., Fortson, L., Furniss, A., Galante, N., Gall, D., Godambe, S., Griffin, S., Grube, J., Gyuk, G., Hanna, D., Holder, J., Huan, H., Hughes, G., Humensky, T. B., Kaaret, P., Karlsson, N., Kertzman, M., Khassen, Y., Kieda, D., Krawczynski, H., Krennrich, F., Lang, M. J., Lee, K., Maier, G., Majumdar, P., McArthur, S., McCann, A., Millis, J., Moriarty, P., Mukherjee, R., Nuñez, P. D, Ong, R. A., Orr, M., Otte, A. N., Pandel, D., Park, N., Perkins, J. S., Pohl, M., 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., Skole, C., Smith, A. W., Staszak, D., Telezhinsky, I., Tešić, G., Theiling, M., Thibadeau, S., Tsurusaki, K., Tyler, J., Varlotta, A., Vincent, S., Vivier, M., Wakely, S. P., Ward, J. E., Weekes, T. C., Weinstein, A., Weisgarber, T., Welsing, R., Williams, D. A., and Zitzer, B.
Subjects: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Astrophysics of Galaxies
Abstract: We report on very high energy (E > 100 GeV) gamma-ray observations of V407 Cygni, a symbiotic binary that underwent a nova outburst producing 0.1-10 GeV gamma rays during 2010 March 10-26. Observations were made with the Very Energetic Radiation Imaging Telescope Array System during 2010 March 19-26 at relatively large zenith angles, due to the position of V407 Cyg. An improved reconstruction technique for large zenith angle observations is presented and used to analyze the data. We do not detect V407 Cygni and place a differential upper limit on the flux at 1.6 TeV of 2.3 \times 10^(-12) erg cm^(-2) s^(-1) (at the 95% confidence level). When considered jointly with data from Fermi-LAT, this result places limits on the acceleration of very high energy particles in the nova., Comment: 17 pages, 4 figures, accepted for publication in ApJ
Published: 2012
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57. Discovery of High-energy and Very High Energy Gamma-ray Emission from the Blazar RBS 0413

Author: VERITAS Collaboration, Aliu, E., Archambault, S., Arlen, T., Aune, T., Beilicke, M., Benbow, W., Boettcher, M., Bouvier, A., Bradbury, S. M., Buckley, J. H., Bugaev, V., Byrum, K., Cannon, A., Cesarini, A., Ciupik, L., Collins-Hughes, E., Connolly, M. P., Coppi, P., Cui, W., Decerprit, G., Dickherber, R., Dumm, J., Errando, M., Falcone, A., Feng, Q., Finley, J. P., Finnegan, G., Fortson, L., Furniss, A., Galante, N., Gall, D., Godambe, S., Griffin, S., Grube, J., Gyuk, G., Hanna, D., Hawkins, K., Holder, J., Huan, H., Hughes, G., Humensky, T. B., Kaaret, P., Karlsson, N., Kertzman, M., Khassen, Y., Kieda, D., Krawczynski, H., Krennrich, F., Lang, M. J., Lee, K., Madhavan, A. S, Maier, G., Majumdar, P., McArthur, S., McCann, A., Moriarty, P., Mukherjee, R., Ong, R. A., Orr, M., Otte, A. N., Palma, N., Park, N., Perkins, J. S., Pichel, A., Pohl, M., 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., Telezhinsky, I., Tesic, G., Theiling, M., Thibadeau, S., Tsurusaki, K., Varlotta, A., Vivier, M., Wakely, S. P., Ward, J. E., Weekes, T. C., Weinstein, A., Weisgarber, T., Williams, D. A., Zitzer, B., Fortin, P., and Horan, D.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: We report on the discovery of high-energy (HE; E > 0.1 GeV) and very high-energy (VHE; E > 100 GeV) gamma-ray emission from the high-frequency-peaked BL Lac object RBS 0413. VERITAS, a ground-based gamma-ray observatory, detected VHE gamma rays from RBS 0413 with a statistical significance of 5.5 standard deviations (sigma) and a gamma-ray flux of (1.5 \pm 0.6stat \pm 0.7syst) \times 10^(-8) photons m^(-2) s^(-1) (\sim 1% of the Crab Nebula flux) above 250 GeV. The observed spectrum can be described by a power law with a photon index of 3.18 \pm 0.68stat \pm 0.30syst. Contemporaneous observations with the Large Area Telescope (LAT) on the Fermi Gamma-ray Space Telescope detected HE gamma rays from RBS 0413 with a statistical significance of more than 9 sigma, a power-law photon index of 1.57 \pm 0.12stat +0.11sys -0.12sys and a gamma-ray flux between 300 MeV and 300 GeV of (1.64 \pm 0.43stat +0.31sys -0.22sys) \times 10^(-5) photons m^(-2) s^(-1). We present the results from Fermi-LAT and VERITAS, including a spectral energy distribution modeling of the gamma-ray, quasi-simultaneous X-ray (Swift-XRT), ultraviolet (Swift-UVOT) and R-band optical (MDM) data. We find that, if conditions close to equipartition are required, both the combined synchrotron self-Compton/external-Compton and the lepto-hadronic models are preferred over a pure synchrotron self-Compton model., Comment: 14 pages, 3 figures, accepted to ApJ, corresponding author: G. D. Senturk
Published: 2012
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58. VERITAS Deep Observations of the Dwarf Spheroidal Galaxy Segue 1

Author: Aliu, E., Archambault, S., 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., Decerprit, G., Dickherber, R., Dumm, J., Errando, M., Falcone, A., Feng, Q., Ferrer, F., Finley, J. P., Finnegan, G., Fortson, L., Furniss, A., Galante, N., Gall, D., Godambe, S., Griffin, S., Grube, J., Gyuk, G., Hanna, D., Holder, J., Huan, H., Hughes, G., Humensky, T. B., Kaaret, P., Karlsson, N., Kertzman, M., Khassen, Y., Kieda, D., Krawczynski, H., Krennrich, F., Lee, K., Madhavan, A. 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, M., 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., Skole, C., Smith, A. W., Staszak, D., Telezhinsky, I., Tesic, G., Theiling, M., Thibadeau, S., Tsurusaki, K., Varlotta, A., Vassiliev, V. V., Vincent, S., Vivier, M., Wagner, R. G., Wakely, S. P., Ward, J. E., Weekes, T. C., Weinstein, A., Weisgarber, T., Williams, D. A., and Zitzer, B.
Subjects: Astrophysics - High Energy Astrophysical Phenomena, High Energy Physics - Experiment
Abstract: The VERITAS array of Cherenkov telescopes has carried out a deep observational program on the nearby dwarf spheroidal galaxy Segue 1. We report on the results of nearly 48 hours of good quality selected data, taken between January 2010 and May 2011. No significant $\gamma$-ray emission is detected at the nominal position of Segue 1, and upper limits on the integrated flux are derived. According to recent studies, Segue 1 is the most dark matter-dominated dwarf spheroidal galaxy currently known. We derive stringent bounds on various annihilating and decaying dark matter particle models. The upper limits on the velocity-weighted annihilation cross-section are $\mathrm{<\sigma v >^{95% CL} \lesssim 10^{-23} cm^{3} s^{-1}}$, improving our limits from previous observations of dwarf spheroidal galaxies by at least a factor of two for dark matter particle masses $\mathrm{m_{\chi}\gtrsim 300 GeV}$. The lower limits on the decay lifetime are at the level of $\mathrm{\tau^{95% CL} \gtrsim 10^{24} s}$. Finally, we address the interpretation of the cosmic ray lepton anomalies measured by ATIC and PAMELA in terms of dark matter annihilation, and show that the VERITAS observations of Segue 1 disfavor such a scenario., Comment: Added recently published erratum at the end of the original article
Published: 2012
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59. VERITAS Observations of day-scale flaring of M87 in 2010 April

Author: 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., 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., 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., LeBohec, S., Madhavan, A. S, Maier, G., Majumdar, P., McArthur, S., McCann, A., Moriarty, P., Mukherjee, R., Nunez, P. D, Ong, R. A., Orr, M., Otte, A. N., Park, N., Perkins, J. S., Pichel, A., Pohl, M., 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., Şentürk, G. D., Skole, C., Staszak, D., Tešić, 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., and Zitzer, B.
Subjects: Astrophysics - Cosmology and Nongalactic Astrophysics
Abstract: VERITAS has been monitoring the very-high-energy (VHE; >100GeV) gamma-ray activity of the radio galaxy M87 since 2007. During 2008, flaring activity on a timescale of a few days was observed with a peak flux of (0.70 +- 0.16) X 10^{-11} cm^{-2} s^{-1} at energies above 350GeV. In 2010 April, VERITAS detected a flare from M87 with peak flux of (2.71 +- 0.68) X 10^{-11} cm^{-2} s^{-1} for E>350GeV. The source was observed for six consecutive nights during the flare, resulting in a total of 21 hr of good quality data. The most rapid flux variation occurred on the trailing edge of the flare with an exponential flux decay time of 0.90^{+0.22}_{-0.15} days. The shortest detected exponential rise time is three times as long, at 2.87^{+1.65}_{-0.99} days. The quality of the data sample is such that spectral analysis can be performed for three periods: rising flux, peak flux, and falling flux. The spectra obtained are consistent with power-law forms. The spectral index at the peak of the flare is equal to 2.19 +- 0.07. There is some indication that the spectrum is softer in the falling phase of the flare than the peak phase, with a confidence level corresponding to 3.6 standard deviations. We discuss the implications of these results for the acceleration and cooling rates of VHE electrons in M87 and the constraints they provide on the physical size of the emitting region., Comment: Accepted for publication in ApJ; 17 pages, 5 figures; Corresponding author: C. M. Hui
Published: 2011
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60. The 2010 very high energy gamma-ray flare & 10 years of multi-wavelength observations of M 87

Author: Collaboration, The H. E. S. S., Abramowski, A., Acero, F., Aharonian, F., Akhperjanian, A. G., Anton, G., Balzer, A., Barnacka, A., de Almeida, U. Barres, Becherini, Y., Becker, J., Behera, B., Bernlöhr, K., Birsin, E., Biteau, J., Bochow, A., Boisson, C., Bolmont, J., Bordas, P., Brucker, J., Brun, F., Brun, P., Bulik, T., Büsching, I., Carrigan, S., Casanova, S., Cerruti, M., Chadwick, P. M., Charbonnier, A., Chaves, R. C. G., Cheesebrough, A., Clapson, A. C., Coignet, G., Cologna, G., Conrad, J., Dalton, M., Daniel, M. K., Davids, I. D., Degrange, B., Deil, C., Dickinson, H. J., Djannati-Ataï, A., Domainko, W., Drury, L. O'C., Dubus, G., Dutson, K., Dyks, J., Dyrda, M., Egberts, K., Eger, P., Espigat, P., Fallon, L., Farnier, C., Fegan, S., Feinstein, F., Fernandes, M. V., Fiasson, A., Fontaine, G., Förster, A., Füßling, M., Gallant, Y. A., Gast, H., Gérard, L., Gerbig, D., Giebels, B., Glicenstein, J. F., Glück, B., Goret, P., Göring, D., Häffner, S., Hague, J. D., Hampf, D., Hauser, M., Heinz, S., Heinzelmann, G., Henri, G., Hermann, G., Hinton, J. A., Hoffmann, A., Hofmann, W., Hofverberg, P., Holler, M., Horns, D., Jacholkowska, A., de Jager, O. C., Jahn, C., Jamrozy, M., Jung, I., Kastendieck, M. A., Katarzyński, K., Katz, U., Kaufmann, S., Keogh, D., Khangulyan, D., Khélifi, B., Klochkov, D., Kluźniak, W., Kneiske, T., Komin, Nu., Kosack, K., Kossakowski, R., Laffon, H., Lamanna, G., Lennarz, D., Lohse, T., Lopatin, A., Lu, C. -C., Marandon, V., Marcowith, A., Masbou, J., Maurin, D., Maxted, N., Mayer, M., McComb, T. J. L., Medina, M. C., Méhault, J., Moderski, R., Moulin, E., Naumann, C. L., Naumann-Godo, M., de Naurois, M., Nedbal, D., Nekrassov, D., Nguyen, N., Nicholas, B., Niemiec, J., Nolan, S. J., Ohm, S., Wilhelmi, E. de Oña, Opitz, B., Ostrowski, M., Oya, I., Panter, M., Arribas, M. Paz, Pedaletti, G., Pelletier, G., Petrucci, P. -O., Pita, S., Pühlhofer, G., Punch, M., Quirrenbach, A., Raue, M., Rayner, S. M., Reimer, A., Reimer, O., Renaud, M., Reyes, R. de los, Rieger, F., Ripken, J., Rob, L., Rosier-Lees, S., Rowell, G., Rudak, B., Rulten, C. B., Ruppel, J., Sahakian, V., Sanchez, D. A., Santangelo, A., Schlickeiser, R., Schöck, F. M., Schulz, A., Schwanke, U., Schwarzburg, S., Schwemmer, S., Sheidaei, F., Skilton, J. L., Sol, H., Spengler, G., Stawarz, Ł., Steenkamp, R., Stegmann, C., Stinzing, F., Stycz, K., Sushch, I., Szostek, A., Tavernet, J. -P., Terrier, R., Tluczykont, M., Valerius, K., van Eldik, C., Vasileiadis, G., Venter, C., Vialle, J. P., Viana, A., Vincent, P., Völk, H. J., Volpe, F., Vorobiov, S., Vorster, M., Wagner, S. J., Ward, M., White, R., Wierzcholska, A., Zacharias, M., Zajczyk, A., Zdziarski, A. A., Zech, A., Zechlin, H. -S., Collaboration, The MAGIC, Aleksić, J., Antonelli, L. A., Antoranz, P., Backes, M., Barrio, J. A., Bastieri, D., González, J. Becerra, Bednarek, W., Berdyugin, A., Berger, K., Bernardini, E., Biland, A., Blanch, O., Bock, R. K., Boller, A., Bonnoli, G., Tridon, D. Borla, Braun, I., Bretz, T., Cañellas, A., Carmona, E., Carosi, A., Colin, P., Colombo, E., Contreras, J. L., Cortina, J., Cossio, L., Covino, S., Dazzi, F., De Angelis, A., del Pozo, E. De Cea, De Lotto, B., Mendez, C. Delgado, Ortega, A. Diago, Doert, M., Domínguez, A., Prester, D. Dominis, Dorner, D., Doro, M., Elsaesser, D., Ferenc, D., Fonseca, M. V., Font, L., Fruck, C., López, R. J. García, Garczarczyk, M., Garrido, D., Giavitto, G., Godinović, N., Hadasch, D., Häfner, D., Herrero, A., Hildebrand, D., Höhne-Mönch, D., Hose, J., Hrupec, D., Huber, B., Jogler, T., Klepser, S., Krähenbühl, T., Krause, J., La Barbera, A., Lelas, D., Leonardo, E., Lindfors, E., Lombardi, S., López, M., Lorenz, E., Makariev, M., Maneva, G., Mankuzhiyil, N., Mannheim, K., Maraschi, L., Mariotti, M., Martínez, M., Mazin, D., Meucci, M., Miranda, J. M., Mirzoyan, R., Miyamoto, H., Moldón, J., Moralejo, A., Munar, P., Nieto, D., Nilsson, K., Orito, R., Paneque, D., Paoletti, R., Pardo, S., Paredes, J. M., Partini, S., Pasanen, M., Pauss, F., Perez-Torres, M. A., Persic, M., Peruzzo, L., Pilia, M., Pochon, J., Prada, F., Moroni, P. G. Prada, Prandini, E., Puljak, I., Reichardt, I., Reinthal, R., Rhode, W., Ribó, M., Rico, J., Rügamer, S., Saggion, A., Saito, K., Saito, T. Y., Salvati, M., Satalecka, K., Scalzotto, V., Scapin, V., Schultz, C., Schweizer, T., Shayduk, M., Shore, S. N., Sillanpää, A., Sitarek, J., Sobczynska, D., Spanier, F., Spiro, S., Stamerra, A., Steinke, B., Storz, J., Strah, N., Surić, T., Takalo, L., Takami, H., Tavecchio, F., Temnikov, P., Terzić, T., Tescaro, D., Teshima, M., Thom, M., Tibolla, O., Torres, D. F., Treves, A., Vankov, H., Vogler, P., Wagner, R. M., Weitzel, Q., Zabalza, V., Zandanel, F., Zanin, R., Collaboration, The VERITAS, Arlen, T., Aune, T., Beilicke, M., Benbow, W., Bouvier, A., Bradbury, S. M., Buckley, J. H., Bugaev, V., Byrum, K., Cannon, A., Cesarini, A., Ciupik, L., 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., Godambe, S., Griffin, S., Grube, J., Gyuk, G., Hanna, D., Holder, J., Huan, H., Hui, C. M., Kaaret, P., Karlsson, N., Kertzman, M., Khassen, Y., Kieda, D., Krawczynski, H., Krennrich, F., Lang, M. J., LeBohec, S., Maier, G., McArthur, S., McCann, A., Moriarty, P., Mukherjee, R., Nuñez, P. D., Ong, R. A., Orr, M., Otte, A. N., Park, N., Perkins, J. S., Pichel, A., Pohl, M., Prokoph, H., Ragan, K., Reyes, L. C., Reynolds, P. T., Roache, E., Rose, H. J., Schroedter, M., Sembroski, G. H., Şentürk, G. D., Telezhinsky, I., Tešić, G., Theiling, M., Thibadeau, S., Varlotta, A., Vassiliev, V. V., Vivier, M., Wakely, S. P., Weekes, T. C., Williams, D. A., Zitzer, B., Cara, M., Casadio, C., Cheung, C. C., McConville, W., Davies, F., Doi, A., Giovannini, G., Giroletti, M., Hada, K., Hardee, P., Harris, D. E., Junor, W., Kino, M., Lee, N. P., Ly, C., Madrid, J., Massaro, F., Mundell, C. G., Nagai, H., Perlman, E. S., Steele, I. A., Walker, R. C., and Wood, D. L.
Subjects: Astrophysics - Cosmology and Extragalactic Astrophysics
Abstract: Abridged: The giant radio galaxy M 87 with its proximity, famous jet, and very massive black hole provides a unique opportunity to investigate the origin of very high energy (VHE; E>100 GeV) gamma-ray emission generated in relativistic outflows and the surroundings of super-massive black holes. M 87 has been established as a VHE gamma-ray emitter since 2006. The VHE gamma-ray emission displays strong variability on timescales as short as a day. In this paper, results from a joint VHE monitoring campaign on M 87 by the MAGIC and VERITAS instruments in 2010 are reported. During the campaign, a flare at VHE was detected triggering further observations at VHE (H.E.S.S.), X-rays (Chandra), and radio (43 GHz VLBA). The excellent sampling of the VHE gamma-ray light curve enables one to derive a precise temporal characterization of the flare: the single, isolated flare is well described by a two-sided exponential function with significantly different flux rise and decay times. While the overall variability pattern of the 2010 flare appears somewhat different from that of previous VHE flares in 2005 and 2008, they share very similar timescales (~day), peak fluxes (Phi(>0.35 TeV) ~= (1-3) x 10^-11 ph cm^-2 s^-1), and VHE spectra. 43 GHz VLBA radio observations of the inner jet regions indicate no enhanced flux in 2010 in contrast to observations in 2008, where an increase of the radio flux of the innermost core regions coincided with a VHE flare. On the other hand, Chandra X-ray observations taken ~3 days after the peak of the VHE gamma-ray emission reveal an enhanced flux from the core. The long-term (2001-2010) multi-wavelength light curve of M 87, spanning from radio to VHE and including data from HST, LT, VLA and EVN, is used to further investigate the origin of the VHE gamma-ray emission. No unique, common MWL signature of the three VHE flares has been identified., Comment: 19 pages, 5 figures; Corresponding authors: M. Raue, L. Stawarz, D. Mazin, P. Colin, C. M. Hui, M. Beilicke; Fig. 1 lightcurve data available online: http://www.desy.de/~mraue/m87/
Published: 2011
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61. VERITAS Collaboration Contributions to the 32nd International Cosmic Ray Conference

Author: The VERITAS Collaboration, Aliu, E., Arlen, T., Aune, T., Beilicke, M., Benbow, W., Böttcher, M., Bouvier, A., 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., Dwarkadas, V. V., 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., Khassen, Y., 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. D, Ong, R. A., Orr, M., Otte, A. N., Park, N., Perkins, J. S., Pichel, A., Pizlo, F., Pohl, M., Prokoph, H., Quinn, J., Ragan, K., Reyes, L. C., Reynolds, P. T., Rovero, A. C., Ruppel, J., Sadun, A. C., Saxon, D. B., Schroedter, M., Sembroski, G. H., Şentürk, G. D., Smith, A. W., Staszak, D., Tešić, 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., and Zitzer, B.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: Compilation of papers contributed by the VERITAS Collaboration to the 32nd International Cosmic Ray Conference, held 11-18 August 2011 in Beijing, China., Comment: 1 html page. ICRC 2011, Beijing, China. A full list of authors and collaborating institutions can be found at http://veritas.sao.arizona.edu/conferences/authors?icrc2011
Published: 2011

62. VERITAS: Status and Highlights

Author: Holder, J., Aliu, E., Arlen, T., Aune, T., Beilicke, M., Benbow, W., Böttcher, M., Bouvier, A., 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., Dwarkadas, V. V., 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., Huan, H., Hughes, G., Hui, C. M., Humensky, T. B., Imran, A., Kaaret, P., Karlsson, N., Kertzman, M., Khassen, Y., 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. D, Ong, R. A., Orr, M., Otte, A. N., Park, N., Perkins, J. S., Pichel, A., Pizlo, F., Pohl, M., Prokoph, H., Quinn, J., Ragan, K., Reyes, L. C., Reynolds, P. T., Rovero, A. C., Ruppel, J., Sadun, A. C., Saxon, D. B., Schroedter, M., Sembroski, G. H., Şentürk, G. D., Smith, A. W., Staszak, D., Tešić, 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., and Zitzer, B.
Subjects: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Instrumentation and Methods for Astrophysics
Abstract: The VERITAS telescope array has been operating smoothly since 2007, and has detected gamma-ray emission above 100 GeV from 40 astrophysical sources. These include blazars, pulsar wind nebulae, supernova remnants, gamma-ray binary systems, a starburst galaxy, a radio galaxy, the Crab pulsar, and gamma-ray sources whose origin remains unidentified. In 2009, the array was reconfigured, greatly improving the sensitivity. We summarize the current status of the observatory, describe some of the scientific highlights since 2009, and outline plans for the future., Comment: Presented at the 32nd ICRC, Beijing, 2011
Published: 2011
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63. VERITAS Observations of Gamma-Ray Bursts Detected by Swift

Author: VERITAS Collaboration, 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, M., 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., Şentürk, G. D., Smith, A. W., Staszak, D., Swordy, S. P., Tešić, 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., and Wood, M.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: We present the results of sixteen Swift-triggered GRB follow-up observations taken with the VERITAS telescope array from January, 2007 to June, 2009. The median energy threshold and response time of these observations was 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 time scale 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 (LAT) on-board the Fermi satellite. No significant 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 (EBL) 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., Comment: 11 pages, 6 figures
Published: 2011
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64. Detection of Pulsed Gamma Rays Above 100 GeV from the Crab Pulsar

Author: VERITAS Collaboration, 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., Nuñez, P., Ong, R. A., Orr, M., Otte, A. N., Park, N., Perkins, J. S., Pizlo, F., Pohl, M., Prokoph, H., Quinn, J., Ragan, K., Reyes, L. C., Reynolds, P. T., Roache, E., Rose, J., Ruppel, J., Saxon, D. B., Schroedter, M., Sembroski, G. H., Şentürk, G. D., Smith, A. W., Staszak, D., Tešić, 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., and Zitzer, B.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: We report the detection of pulsed gamma rays from the Crab pulsar at energies above 100 Gigaelectronvolts (GeV) with the 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 Megaelectronvolts (MeV) 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., Comment: 17 pages, corresponding authors: Nepomuk Otte nepomuk.otte@gmail.com; Andrew McCann mccann@hep.physics.mcgill.ca; Martin Schroedter schroedter@veritas.sao.arizona.edu
Published: 2011
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65. The Track Imaging Cerenkov Experiment

Author: Wissel, S. A., Byrum, K., Cunningham, J. D., Drake, G., Hays, E., Horan, D., Kieda, D., Kovacs, E., Magill, S., Nodulman, L., Swordy, S. P., Wagner, R., and Wakely, S. P.
Subjects: Astrophysics - Instrumentation and Methods for Astrophysics, Astrophysics - High Energy Astrophysical Phenomena
Abstract: We describe a dedicated cosmic-ray telescope that explores a new method for detecting Cerenkov radiation from high-energy primary cosmic rays and the large particle air shower they induce upon entering the atmosphere. Using a camera comprising 16 multi-anode photomultiplier tubes for a total of 256 pixels, the Track Imaging Cerenkov Experiment (TrICE) resolves substructures in particle air showers with 0.086 degree resolution. Cerenkov radiation is imaged using a novel two-part optical system in which a Fresnel lens provides a wide-field optical trigger and a mirror system collects delayed light with four times the magnification. TrICE records well-resolved cosmic-ray air showers at rates ranging between 0.01-0.1 Hz., Comment: 18 pages, 10 figures
Published: 2011
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66. TeV and Multi-wavelength Observations of Mrk 421 in 2006-2008

Author: Acciari, V. A., Aliu, E., Arlen, T., Aune, T., Beilicke, M., Benbow, W., Boltuch, D., Bradbury, S. M., Buckley, J. H., Bugaev, V., Byrum, K., Cannon, A., Cesarini, A., Ciupik, L., Cui, W., Dickherber, R., Duke, C., Falcone, A., Finley, J. P., Finnegan, G., Fortson, L., Furniss, A., Galante, N., Gall, D., Gillanders, G. H., Godambe, S., Grube, J., Guenette, R., Gyuk, G., Hanna, D., Holder, J., Hui, C. M., Humensky, T. B., Imran, A., Kaaret, P., Karlsson, N., Kertzman, M., Kieda, D., Konopelko, A., Krawczynski, H., Krennrich, F., Lang, M. J., Maier, G., McArthur, S., McCutcheon, M., Moriarty, P., Ong, R. A., Otte, A. N., Ouellette, M., Pandel, D., Perkins, J. S., Pichel, A., Pohl, M., Quinn, J., Ragan, K., Reyes, L. C., Reynolds, P. T., Roache, E., Rose, H. J., Rovero, A. C., Schroedter, M., Sembroski, G. H., Senturk, G. Demet, Steele, D., Swordy, S. P., Theiling, M., Thibadeau, S., Varlotta, A., Vassiliev, V. V., Vincent, S., Wagner, R. G., Wakely, S. P., Ward, J. E., Weekes, T. C., Weinstein, A., Weisgarber, T., Williams, D. A., Wissel, S., Wood, M., Zitzer, B., Garson, A., Lee, K., Sadun, A. C., Carini, M., Barnaby, D., Cook, K., Maune, J., Pease, A., Smith, S., Walters, R., Berdyugin, A., Lindfors, E., Nilsson, K., Pasanen, M., Sainio, J., Sillanpaa, A., Takalo, L. O., Villforth, C., Montaruli, T., Baker, M., Lahteenmaki, A., Tornikoski, M., Hovatta, T., Nieppola, E., Aller, H. D., and Aller, M. F.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: We report on TeV gamma-ray observations of the blazar Mrk 421 (redshift of 0.031) with the VERITAS observatory and the Whipple 10m Cherenkov telescope. The excellent sensitivity of VERITAS allowed us to sample the TeV gamma-ray fluxes and energy spectra with unprecedented accuracy where Mrk 421 was detected in each of the pointings. A total of 47.3 hrs of VERITAS and 96 hrs of Whipple 10m data were acquired between January 2006 and June 2008. We present the results of a study of the TeV gamma-ray energy spectra as a function of time, and for different flux levels. On May 2nd and 3rd, 2008, bright TeV gamma-ray flares were detected with fluxes reaching the level of 10 Crab. The TeV gamma-ray data were complemented with radio, optical, and X-ray observations, with flux variability found in all bands except for the radio waveband. The combination of the RXTE and Swift X-ray data reveal spectral hardening with increasing flux levels, often correlated with an increase of the source activity in TeV gamma-rays. Contemporaneous spectral energy distributions were generated for 18 nights, each of which are reasonably described by a one-zone SSC model., Comment: 30 pages, 12 figures, accepted by ApJ
Published: 2011
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67. VERITAS Observations of the TeV Binary LS I +61 303 During 2008-2010

Author: 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, M., 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. Demet, 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., and Zitzer, B.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: We present the results of observations of the TeV binary LS I +61 303 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 October 2008 and December 2010 a total exposure of 64.5 hours was accumulated with VERITAS on LS I +61 303, resulting in an excess at the 3.3 sigma significance level for constant emission over the entire integrated dataset. 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 +61 303 by the Swift X-ray Telescope (XRT) and the Rossi X-ray Timing Explorer Timing (RXTE) Proportional Counter Array (PCA). 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 (LAT)., Comment: Accepted for Publication in The Astrophysical Journal, 21 pages, 3 tables, 6 figures
Published: 2011
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68. Gamma-ray observations of the Be/pulsar binary 1A 0535+262 during a giant X-ray outburst

Author: VERITAS collaboration, Acciari, V. A., Aliu, E., Araya, M., 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., Falcone, A., Finley, J. P., Fortson, L., Furniss, A., Galante, N., Gall, D., Godambe, S., Griffin, S., Guenette, R., Gyuk, G., Hanna, D., Holder, J., Hughes, G., Hui, C. M., Humensky, T. B., Imran, A., Kaaret, P., Kertzman, M., Krawczynski, H., Krennrich, F., Madhavan, A. S., Maier, G., Majumdar, P., McArthur, S., Moriarty, P., Ong, R. A., Otte, A. N., Pandel, D., Park, N., Perkins, J. S., Pohl, M., Prokoph, H., Quinn, J., Ragan, K., Reyes, L. C., Reynolds, P. T., Roache, E., Rose, H. J., Saxon, D. B., Sembroski, G. H., Senturk, G. Demet, Smith, A. W., Tešić, G., Theiling, M., Thibadeau, S., Varlotta, A., Vincent, S., Vivier, M., Wakely, S. P., Ward, J. E., Weekes, T. C., Weinstein, A., Weisgarber, T., Weng, S., Williams, D. A., Wood, M., and Zitzer, B.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: Giant X-ray outbursts, with luminosities of about $ 10^{37}$ erg s$^{-1}$, are observed roughly every 5 years from the nearby Be/pulsar binary 1A 0535+262. In this article, we present observations of the source with VERITAS at very-high energies (VHE; E$>$100 GeV) triggered by the X-ray outburst in December 2009. The observations started shortly after the onset of the outburst, and they provided comprehensive coverage of the episode, as well as the 111-day binary orbit. No VHE emission is evident at any time. We also examined data from the contemporaneous observations of 1A 0535+262 with the Fermi/LAT at high energy photons (HE; E$>$0.1 GeV) and failed to detect the source at GeV energies. The X-ray continua measured with the Swift/XRT and the RXTE/PCA can be well described by the combination of blackbody and Comptonized emission from thermal electrons. Therefore, the gamma-ray and X-ray observations suggest the absence of a significant population of non-thermal particles in the system. This distinguishes 1A~0535+262 from those Be X-ray binaries (such as PSR B1259--63 and LS I +61$^{\circ}$303) that have been detected at GeV--TeV energies. We discuss the implications of the results on theoretical models., Comment: 28 pages, 4 figures; accepted by The Astrophysical Journal updated references
Published: 2011
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69. Discovery of TeV Gamma Ray Emission from Tycho's Supernova Remnant

Author: 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., Perkins, J. S., Pohl, M., 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., Tešić, 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., and Zitzer, B.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: We report the discovery of TeV gamma-ray emission from the Type Ia supernova remnant (SNR) G120.1+1.4, known as Tycho's supernova remnant. 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 $00^{\rm h} \ 25^{\rm m} \ 27.0^{\rm s},\ +64^{\circ} \ 10^{\prime} \ 50^{\prime\prime}$ (J2000). The TeV photon spectrum measured by VERITAS can be described with a power-law $dN/dE = C(E/3.42\;\textrm{TeV})^{-\Gamma}$ with $\Gamma = 1.95 \pm 0.51_{stat} \pm 0.30_{sys}$ and $C = (1.55 \pm 0.43_{stat} \pm 0.47_{sys}) \times 10^{-14}$ cm$^{-2}$s$^{-1}$TeV$^{-1}$. The integral flux above 1 TeV corresponds to $\sim 0.9%$ percent 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 which can describe the data. The lowest magnetic field allowed in these models is $\sim 80 \mu$G, which may be interpreted as evidence for magnetic field amplification., Comment: 6 pages, 3 figures. Accepted in ApJL
Published: 2011
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70. VERITAS Search for VHE Gamma-ray Emission from Dwarf Spheroidal Galaxies

Author: The VERITAS Collaboration, Acciari, V. A., Arlen, T., Aune, T., Beilicke, M., Benbow, W., Boltuch, D., Bradbury, S. M., Buckley, J. H., Bugaev, V., Byrum, K., Cannon, A., Cesarini, A., Christiansen, J. L., Ciupik, L., Cui, W., Dickherber, R., Duke, C., Finley, J. P., Finnegan, G., Furniss, A., Galante, N., Godambe, S., Grube, J., Guenette, R., Gyuk, G., Hanna, D., Holder, J., Hui, C. M., Humensky, T. B., Imran, A., Kaaret, P., Karlsson, N., Kertzman, M., Kieda, D., Konopelko, A., Krawczynski, H., Krennrich, F., Maier, G., McArthur, S., McCann, A., McCutcheon, M., Moriarty, P., Ong, R. A., Otte, A. N., Pandel, D., Perkins, J. S., Pohl, M., Quinn, J., Ragan, K., Reyes, L. C., Reynolds, P. T., Roache, E., Rose, H. J., Schroedter, M., Sembroski, G. H., Senturk, G. Demet, Smith, A. W., Steele, D., Swordy, S. P., Tešić, G., Theiling, M., Thibadeau, S., Varlotta, A., Vassiliev, V. V., Vincent, S., Wagner, R. G., Wakely, S. P., Ward, J. E., Weekes, T. C., Weinstein, A., Weisgarber, T., Williams, D. A., Wissel, S., Wood, M. D., and Zitzer, B.
Subjects: Astrophysics - Cosmology and Nongalactic Astrophysics
Abstract: Indirect dark matter searches with ground-based gamma-ray observatories provide an alternative for identifying the particle nature of dark matter that is complementary to that of direct search or accelerator production experiments. We present the results of observations of the dwarf spheroidal galaxies Draco, Ursa Minor, Bootes 1, and Willman 1 conducted by VERITAS. These galaxies are nearby dark matter dominated objects located at a typical distance of several tens of kiloparsecs for which there are good measurements of the dark matter density profile from stellar velocity measurements. Since the conventional astrophysical background of very high energy gamma rays from these objects appears to be negligible, they are good targets to search for the secondary gamma-ray photons produced by interacting or decaying dark matter particles. No significant gamma-ray flux above 200 GeV was detected from these four dwarf galaxies for a typical exposure of ~20 hours. The 95% confidence upper limits on the integral gamma-ray flux are in the range 0.4-2.2x10^-12 photons cm^-2s^-1. We interpret this limiting flux in the context of pair annihilation of weakly interacting massive particles and derive constraints on the thermally averaged product of the total self-annihilation cross section and the relative velocity of the WIMPs. The limits are obtained under conservative assumptions regarding the dark matter distribution in dwarf galaxies and are approximately three orders of magnitude above the generic theoretical prediction for WIMPs in the minimal supersymmetric standard model framework. However significant uncertainty exists in the dark matter distribution as well as the neutralino cross sections which under favorable assumptions could further lower the limits., Comment: 21 pages, 2 figures, updated to reflect version published in ApJ. NOTE: M.D. Wood added as author
Published: 2010
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71. VERITAS 2008 - 2009 monitoring of the variable gamma-ray source M87

Author: The VERITAS Collaboration, Acciari, V. A., Aliu, E., Arlen, T., Aune, T., Beilicke, M., Benbow, W., Boltuch, D., Bradbury, S. M., Buckley, J. H., Bugaev, V., Byrum, K., Cannon, A., Cesarini, A., Chow, Y. C., Ciupik, L., Cogan, P., Cui, W., Dickherber, R., Duke, C., Finley, J. P., Finnegan, G., Fortin, P., Fortson, L., Furniss, A., Galante, N., Gall, D., Gillanders, G. H., Godambe, S., Grube, J., Guenette, R., Gyuk, G., Hanna, D., Holder, J., Hui, C. M., Humensky, T. B., Imran, A., Kaaret, P., Karlsson, N., Kertzman, M., Kieda, D., Konopelko, A., Krawczynski, H., Krennrich, F., Lang, M. J., LeBohec, S., Maier, G., McArthur, S., McCann, A., McCutcheon, M., Millis, J., Moriarty, P., Ong, R. A., Otte, A. N., Pandel, D., Perkins, J. S., Quinn, A. M. J., Ragan, K., Reyes, L. C., Reynolds, P. T., Roache, E., Rose, H. J., Rovero, A. C., Schroedter, M., Sembroski, G. H., Senturk, G. Demet, Smith, A. W., Steele, D., Swordy, S. P., Theiling, M., Thibadeau, S., Varlotta, A., Vincent, S., Wagner, R. G., Wakely, S. P., Ward, J. E., Weekes, T. C., Weinstein, A., Weisgarber, T., Williams, D. A., Wissel, S., Wood, M., Zitzer, B., Monitoring, Chandra M87, Harris, D. E., and Massaro, F.
Subjects: Astrophysics - Cosmology and Nongalactic Astrophysics, Astrophysics - High Energy Astrophysical Phenomena
Abstract: M87 is a nearby radio galaxy that is detected at energies ranging from radio to VHE gamma-rays. Its proximity and its jet, misaligned from our line-of-sight, enable detailed morphological studies and extensive modeling at radio, optical, and X-ray energies. Flaring activity was observed at all energies, and multi-wavelength correlations would help clarify the origin of the VHE emission. In this paper, we describe a detailed temporal and spectral analysis of the VERITAS VHE gamma-ray observations of M87 in 2008 and 2009. In the 2008 observing season, VERITAS detected an excess with a statistical significance of 7.2 sigma from M87 during a joint multi-wavelength monitoring campaign conducted by three major VHE experiments along with the Chandra X-ray Observatory. In February 2008, VERITAS observed a VHE flare from M87 occurring over a 4-day timespan. The peak nightly flux above 250GeV was 7.7% of the Crab Nebula flux. M87 was marginally detected before this 4-day flare period, and was not detected afterwards. Spectral analysis of the VERITAS observations showed no significant change in the photon index between the flare and pre-flare states. Shortly after the VHE flare seen by VERITAS, the Chandra X-ray Observatory detected the flux from the core of M87 at a historical maximum, while the flux from the nearby knot HST-1 remained quiescent. Acciari et al. (2009) presented the 2008 contemporaneous VHE gamma-ray, Chandra X-ray, and VLBA radio observations which suggest the core as the most likely source of VHE emission, in contrast to the 2005 VHE flare that was simultaneous with an X-ray flare in the HST-1 knot. In 2009, VERITAS continued its monitoring of M87 and marginally detected a 4.2 sigma excess corresponding to a flux of ~1% of the Crab Nebula. No VHE flaring activity was observed in 2009., Comment: 17 pages, 5 figures, accepted for publication in ApJ
Published: 2010
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72. Discovery of VHE $\gamma$-ray emission from the SNR G54.1+0.3

Author: Acciari, V. A., Aliu, E., Arlen, T., Aune, T., Bautista, M., Beilicke, M., Benbow, W., Boltuch, D., Bradbury, S. M., Buckley, J. H., Bugaev, V., Butt, Y., Byrum, K., Cesarini, A., Ciupik, L., Cui, W., Dickherber, R., Duke, C., Finley, J. P., Finnegan, G., Fortson, L., Furniss, A., Galante, N., Gall, D., Gillanders, G. H., Godambe, S., Gotthelf, E. V., Grube, J., Guenette, R., Gyuk, G., Hanna, D., Holder, J., Hui, C. M., Humensky, T. B., Imran, A., Kaaret, P., Karlsson, N., Kertzman, M., Kieda, D., Konopelko, A., Krawczynski, H., Krennrich, F., Lang, M. J., LeBohec, S., Maier, G., McArthur, S., McCann, A., McCutcheon, M., Moriarty, P., Muhkerjee, R., Ong, R. A., Otte, A. N., Pandel, D., Perkins, J. S., Pohl, M., Quinn, J., Ragan, K., Reyes, L. C., Reynolds, P. T., Roache, E., Rose, H. J., Schroedter, M., Sembroski, G. H., Senturk, G. Demet, Slane, P., Smith, A. W., Steele, D., Swordy, S. P., Těsić, G., Theiling, M., Thibadeau, S., Vassiliev, V. V., Vincent, S., Wakely, S. P., Ward, J. E., Weekes, T. C., Weinstein, A., Weisgarber, T., Williams, D. A., Wissel, S., Wood, M., and Zitzer, B.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: We report the discovery of very high energy gamma-ray emission from the direction of the SNR G54.1+0.3 using the VERITAS ground-based gamma-ray observatory. The TeV signal has an overall significance of 6.8$\sigma$ and appears point-like given the 5$^{arcminute}$ resolution of the instrument. The integral flux above 1 TeV is 2.5% of the Crab Nebula flux and significant emission is measured between 250 GeV and 4 TeV, well described by a power-law energy spectrum dN/dE $\sim$ E$^{-\Gamma}$ with a photon index $\Gamma= 2.39\pm0.23_{stat}\pm0.30_{sys}$. We find no evidence of time variability among observations spanning almost two years. Based on the location, the morphology, the measured spectrum, the lack of variability and a comparison with similar systems previously detected in the TeV band, the most likely counterpart of this new VHE gamma-ray source is the PWN in the SNR G54.1+0.3. The measured X-ray to VHE gamma-ray luminosity ratio is the lowest among all the nebulae supposedly driven by young rotation-powered pulsars, which could indicate a particle-dominated PWN., Comment: 5 pages, 2 figure, Latex, emulateapj style, accepted by the Astrophysical Journal Letters
Published: 2010
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73. The Discovery of gamma-Ray Emission From The Blazar RGB J0710+591

Author: Acciari, V. A., Aliu, E., Arlen, T., Aune, T., Bautista, M., Beilicke, M., Benbow, W., Böttcher, M., Boltuch, D., Bradbury, S. M., Buckley, J. H., Bugaev, V., Byrum, K., Cannon, A., Cesarini, A., Ciupik, L., Cui, W., Dickherber, R., Duke, C., Falcone, A., Finley, J. P., Finnegan, G., Fortson, L., Furniss, A., Galante, N., Gall, D., Gibbs, K., Gillanders, G. H., Godambe, S., Grube, J., Guenette, R., Gyuk, G., Hanna, D., Holder, J., Hui, C. M., Humensky, T. B., Imran, A., Kaaret, P., Karlsson, N., Kertzman, M., Kieda, D., Konopelko, A., Krawczynski, H., Krennrich, F., Lang, M. J., Lamerato, A., LeBohec, S., Maier, G., McArthur, S., McCann, A., McCutcheon, M., Moriarty, P., Mukherjee, R., Ong, R. A., Otte, A. N., Pandel, D., Perkins, J. S., Petry, D., Pichel, A., Pohl, M., Quinn, J., Ragan, K., Reyes, L. C., Reynolds, P. T., Roache, E., Rose, H. J., Roustazadeh, P., Schroedter, M., Sembroski, G. H., Senturk, G. Demet, Smith, A. W., Steele, D., Swordy, S. P., Tešić, G., Theiling, M., Thibadeau, S., Varlotta, A., Vassiliev, V. V., Vincent, S., Wagner, R. G., Wakely, S. P., Ward, J. E., Weekes, T. C., Weinstein, A., Weisgarber, T., Williams, D. A., Wissel, S., Wood, M., Zitzer, B., Ackermann, M., Ajello, M., Antolini, E., Baldini, L., Ballet, J., Barbiellini, G., Bastieri, D., Bechtol, K., Bellazzini, R., Berenji, B., Blandford, R. D., Bloom, E. D., Bonamente, E., Borgland, A. W., Bouvier, A., Bregeon, J., Brigida, M., Bruel, P., Buehler, R., Buson, S., Caliandro, G. A., Cameron, R. A., Caraveo, P. A., Carrigan, S., Casandjian, J. M., Cavazzuti, E., Cecchi, C., Çelik, Ö., Charles, E., Chekhtman, A., Cheung, C. C., Chiang, J., Ciprini, S., Claus, R., Cohen-Tanugi, J., Conrad, J., Dermer, C. D., de Palma, F., Silva, E. do Couto e, Drell, P. S., Dubois, R., Dumora, D., Farnier, C., Favuzzi, C., Fegan, S. J., Fortin, P., Frailis, M., Fukazawa, Y., Funk, S., Fusco, P., Gargano, F., Gasparrini, D., Gehrels, N., Germani, S., Giebels, B., Giglietto, N., Giordano, F., Giroletti, M., Glanzman, T., Godfrey, G., Grenier, I. A., Grove, J. E., Guiriec, S., Hays, E., Horan, D., Hughes, R. E., Jóhannesson, G., Johnson, A. S., Johnson, W. N., Kamae, T., Katagiri, H., Kataoka, J., Knödlseder, J., Kuss, M., Lande, J., Latronico, L., Lee, S. -H., Garde, M. Llena, Longo, F., Loparco, F., Lott, B., Lovellette, M. N., Lubrano, P., Makeev, A., Mazziotta, M. N., Michelson, P. F., Mitthumsiri, W., Mizuno, T., Moiseev, A. A., Monte, C., Monzani, M. E., Morselli, A., Moskalenko, I. V., Murgia, S., Nolan, P. L., Norris, J. P., Nuss, E., Ohno, M., Ohsugi, T., Omodei, N., Orlando, E., Ormes, J. F., Paneque, D., Panetta, J. H., Pelassa, V., Pepe, M., Pesce-Rollins, M., Piron, F., Porter, T. A., Rainò, S., Rando, R., Razzano, M., Reimer, A., Reimer, O., Ripken, J., Rodriguez, A. Y., Roth, M., Sadrozinski, H. F. -W., Sanchez, D., Sander, A., Scargle, J. D., Sgrò, C., Siskind, E. J., Smith, P. D., Spandre, G., Spinelli, P., Strickman, M. S., Suson, D. J., Takahashi, H., Tanaka, T., Thayer, J. B., Thayer, J. G., Thompson, D. J., Tibaldo, L., Torres, D. F., Tosti, G., Tramacere, A., Usher, T. L., Vasileiou, V., Vilchez, N., Vitale, V., Waite, A. P., Wang, P., Winer, B. L., Wood, K. S., Yang, Z., Ylinen, T., and Ziegler, M.
Subjects: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Cosmology and Nongalactic Astrophysics
Abstract: The high-frequency-peaked BL Lacertae object RGB J0710+591 was observed in the very high-energy (VHE; E > 100 GeV) wave band by the VERITAS array of atmospheric Cherenkov telescopes. The observations, taken between 2008 December and 2009 March and totaling 22.1 hr, yield the discovery of VHE gamma rays from the source. RGB J0710+591 is detected at a statistical significance of 5.5 standard deviations (5.5{\sigma}) above the background, corresponding to an integral flux of (3.9 +/- 0.8) x 10-12 cm-2 s-1 (3% of the Crab Nebula's flux) above 300 GeV. The observed spectrum can be fit by a power law from 0.31 to 4.6 TeV with a photon spectral index of 2.69 +/- 0.26stat +/- 0.20sys. These data are complemented by contemporaneous multiwavelength data from the Fermi Large Area Telescope, the Swift X-ray Telescope, the Swift Ultra-Violet and Optical Telescope, and the Michigan-Dartmouth-MIT observatory. Modeling the broadband spectral energy distribution (SED) with an equilibrium synchrotron self-Compton model yields a good statistical fit to the data. The addition of an external-Compton component to the model does not improve the fit nor brings the system closer to equipartition. The combined Fermi and VERITAS data constrain the properties of the high-energy emission component of the source over 4 orders of magnitude and give measurements of the rising and falling sections of the SED.
Published: 2010
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74. Studying the Underlying Event in Drell-Yan and High Transverse Momentum Jet Production at the Tevatron

Author: The CDF Collaboration, Aaltonen, T., Adelman, J., Gonzalez, B. Alvarez, Amerio, S., Amidei, D., Anastassov, A., Annovi, A., Antos, J., Apollinari, G., Apresyan, A., Arisawa, T., Artikov, A., Asaadi, J., Ashmanskas, W., Attal, A., Aurisano, A., Azfar, F., Badgett, W., Barbaro-Galtieri, A., Barnes, V. E., Barnett, B. A., Barria, P., Bartos, P., Bauer, G., Beauchemin, P. -H., Bedeschi, F., Beecher, D., Behari, S., Bellettini, G., Bellinger, J., Benjamin, D., Beretvas, A., Berge, D., Bhatti, A., Binkley, M., Bisello, D., Bizjak, I., Blair, R. E., Blocker, C., Blumenfeld, B., Bocci, A., Bodek, A., Boisvert, V., Bortoletto, D., Boudreau, J., Boveia, A., Brau, B., Bridgeman, A., Brigliadori, L., Bromberg, C., Brubaker, E., Budagov, J., Budd, H. S., Budd, S., Burkett, K., Busetto, G., Bussey, P., Buzatu, A., Byrum, K. L., Cabrera, S., Calancha, C., Camarda, S., Campanelli, M., Campbell, M., Canelli, F., Canepa, A., Carls, B., Carlsmith, D., Carosi, R., Carrillon, S., Carron, S., Casal, B., Casarsa, M., Castrocc, A., Catastini, P., Cauz, D., Cavaliere, V., Cavalli-Sforza, M., Cerri, A., Cerrito, L., Chang, S. H., Chen, Y. C., Chertok, M., Chiarelli, G., Chlachidze, G., Chlebana, F., Cho, K., Chokheli, D., Chou, J. P., Chungo, K., Chung, W. H., Chung, Y. S., Chwalek, T., Ciobanu, C. I., Ciocci, M. A., Clark, A., Clark, D., Compostella, G., Convery, M. E., Conway, J., Corbo, M., Cordelli, M., Cox, C. A., Cox, D. J., Crescioli, F., Almenar, C. Cuenca, Cuevas, J., Culbertson, R., Cully, J. C., Dagenhart, D., Datta, M., Davies, T., de Barbaro, P., De Cecco, S., Deisher, A., De Lorenzo, G., Dell'Orso, M., Deluca, C., Demortier, L., Deng, J., Deninno, M., d'Errico, M., Di Canto, A., di Giovanni, G. P., Di Ruzza, B., Dittmann, J. R., D'Onofrio, M., Donati, S., Dong, P., Dorigo, T., Dube, S., Ebina, K., Elagin, A., Erbacher, R., Errede, D., Errede, S., Ershaidat, N., Eusebi, R., Fang, H. C., Farrington, S., Fedorko, W. T., Feild, R. G., Feindt, M., Fernandez, J. P., Ferrazza, C., Field, R., Flanagans, G., Forrest, R., Frank, M. J., Franklin, M., Freeman, J. C., Furic, I., Gallinaro, M., Galyardt, J., Garberson, F., Garcia, J. E., Garfinkel, A. F., Garosi, P., Gerberich, H., Gerdes, D., Gessler, A., Giagu, S., Giakoumopoulou, V., Giannetti, P., Gibson, K., Gimmell, J. L., Ginsburg, C. M., Giokaris, N., Giordani, M., Giromini, P., Giunta, M., Giurgiu, G., Glagolev, V., Glenzinski, D., Gold, M., Goldschmidt, N., Golossanov, A., Gomez, G., Gomez-Ceballos, G., Goncharov, M., González, O., Gorelov, I., Goshaw, A. T., Goulianos, K., Gresele, A., Grinstein, S., Grosso-Pilcher, C., Group, R. C., Grundler, U., da Costa, J. Guimaraes, Gunay-Unalan, Z., Haber, C., Hahn, S. R., Halkiadakis, E., Han, B. -Y., Han, J. Y., Happacher, F., Hara, K., Hare, D., Hare, M., Harr, R. F., Hartz, M., Hatakeyama, K., Hays, C., Heck, M., Heinrich, J., Herndon, M., Heuser, J., Hewamanage, S., Hickman, M., Hidas, D., Hill, C. S., Hirschbuehl, D., Hocker, A., Hou, S., Houlden, M., Hsu, S. -C., Hughes, R. E., Hurwitz, M., Husemann, U., Hussein, M., Huston, J., Incandela, J., Introzzi, G., Iori, M., Ivanov, A., James, E., Jang, D., Jayatilaka, B., Jeon, E. J., Jha, M. K., Jindariani, S., Johnson, W., Jones, M., Joo, K. K., Jun, S. Y., Jung, J. E., Junk, T. R., Kamon, T., Kar, D., Karchin, P. E., Kato, Y., Kephart, R., Ketchum, W., Keung, J., Khotilovich, V., Kilminster, B., Kim, D. H., Kim, H. S., Kim, H. W., Kim, J. E., Kim, M. J., Kim, S. B., Kim, S. H., Kim, Y. K., Kimura, N., Kirsch, L., Klimenko, S., Kondo, K., Kong, D. J., Konigsberg, J., Korytov, A., Kotwal, A. V., Kreps, M., Kroll, J., Krop, D., Krumnack, N., Kruse, M., Krutelyov, V., Kuhr, T., Kulkarni, N. P., Kurata, M., Kwang, S., Laasanen, A. T., Lami, S., Lammel, S., Lancaster, M., Lander, R. L., Lannon, K., Lath, A., Latino, G., Lazzizzera, I., LeCompte, T., Lee, E., Lee, H. S., Lee, J. S., Lee, S. W., Leone, S., Lewis, J. D., Lin, C. -J., Linacre, J., Lindgren, M., Lipeles, E., Lister, A., Litvintsev, D. O., Liu, C., Liu, T., Lockyer, N. S., Loginov, A., Lovas, L., Lucchesi, D., Lueck, J., Lujan, P., Lukens, P., Lungu, G., Lys, J., Lysak, R., MacQueen, D., Madrak, R., Maeshima, K., Makhoul, K., Maksimovic, P., Malde, S., Malik, S., Manca, G., Manousakis-Katsikakis, A., Margaroli, F., Marino, C., Marino, C. P., Martin, A., Martink, V., Martinez, M., Martinez-Ballarin, R., Mastrandrea, P., Mathis, M., Mattson, M. E., Mazzanti, P., McFarland, K. S., McIntyre, P., McNulty, R., Mehta, A., Mehtala, P., Menzione, A., Mesropian, C., Miao, T., Mietlicki, D., Miladinovic, N., Miller, R., Mills, C., Milnik, M., Mitra, A., Mitselmakher, G., Miyake, H., Moed, S., Moggi, N., Mondragon, M. N., Moon, C. S., Moore, R., Morello, M. J., Morlock, J., Fernandez, P. Movilla, Mulmenstadt, J., Mukherjee, A., Muller, Th., Murat, P., Mussini, M., Nachtman, J., Nagai, Y., Naganoma, J., Nakamura, K., Nakano, Napier, A., Nett, J., Neu, C., Neubauer, M. S., Neubauer, S., Nielseng, J., Nodulman, L., Norman, M., Norniella, O., Nurse, E., Oakes, L., Oh, S. H., Oh, Y. D., Oksuzian, I., Okusawa, T., Orava, R., Osterberg, K., Griso, S. Pagan, Pagliarone, C., Palencia, E., Papadimitriou, V., Papaikonomou, A., Paramanov, A. A., Parks, B., Pashapour, S., Patrick, J., Pauletta, G., Paulini, M., Paus, C., Peiffer, T., Pellett, D. E., Penzo, A., Phillips, T. J., Piacentino, G., Pianori, E., Pinera, L., Pitts, K., Plager, C., Pondrom, L., Potamianos, K., Poukhov, O., Prokoshin, F., Pronko, A., Ptohos, F., Pueschel, E., Punzi, G., Pursley, J., Rademacker, J., Rahaman, A., Ramakrishnan, V., Ranjan, N., Redondo, I., Renton, P., Renz, M., Rescigno, M., Richter, S., Rimondi, F., Ristori, L., Robson, A., Rodrigo, T., Rodriguez, T., Rogers, E., Rolli, S., Roser, R., Rossi, M., Rossin, R., Roy, P., Ruiz, A., Russ, J., Rusu, V., Rutherford, B., Saarikko, H., Safonov, A., Sakumoto, W. K., Santi, L., Sartori, L., Sato, K., Savoy-Navarro, A., Schlabach, P., Schmidt, A., Schmidt, E. E., Schmidt, M. A., Schmidt, M. P., Schmitt, M., Schwarz, T., Scodellaro, L., Scribano, A., Scuri, F., Sedov, A., Seidel, S., Seiya, Y., Semenov, A., Sexton-Kennedy, L., Sforza, F., Sfyrla, A., Shalhout, S. Z., Shears, T., Shepard, P. F., Shimojima, M., Shiraishi, S., Shochet, M., Shon, Y., Shreyber, I., Simonenko, A., Sinervo, P., Sisakyan, A., Slaughter, A. J., Slaunwhite, J., Sliwa, K., Smith, J. R., Snider, F. D., Snihur, R., Soha, A., Somalwar, S., Sorin, V., Squillacioti, P., Stanitzki, M., Denis, R. St., Stelzer, B., Stelzer-Chilton, O., Stentz, D., Strologas, J., Strycker, G. L., Suh, J. S., Sukhanov, A., Suslov, I., Taffard, A., Takashima, R., Takeuchi, Y., Tanaka, R., Tang, J., Tecchio, M., Teng, P. K., Thom, J., Thome, J., Thompson, G. A., Thomson, E., Tipton, P., Ttito-Guzmán, P., Tkaczyk, S., Toback, D., Tokar, S., Tollefson, K., Tomura, T., Tonelli, D., Torre, S., Torretta, D., Totaro, P., Tourneur, S., Trovato, M., Tsai, S. -Y., Tu, Y., Turiniff, N., Ukegawa, F., Uozumi, S., van Remortel, N., Varganov, A., Vataga, E., Vázquez, F., Velev, G., Vellidis, C., Vidal, M., Vila, I., Vilar, R., Vogel, M., Volobouev, I., Volpi, G., Wagner, P., Wagner, R. G., Wagner, R. L., Wagner, W., Wagner-Kuhr, J., Wakisaka, T., Wallny, R., Wang, S. M., Warburton, A., Waters, D., Weinberger, M., Weinelt, J., Wester III, W. C., Whitehouse, B., Whiteson, D., Wicklund, A. B., Wicklund, E., Wilbur, S., Williams, G., Williams, H. H., Wilson, M. G., Wilson, P., Winer, B. L., Wittich, P., Wolbers, S., Wolfe, C., Wolfe, H., Wright, T., Wu, X., Würthwein, F., Yagil, A., Yamamoto, K., Yamaoka, J., Yang, U. K., Yang, Y. C., Yao, W. M., Yeh, G. P., Yio, K., Yoh, J., Yorita, K., Yoshidal, T., Yu, G. B., Yu, I., Yu, S. S., Yun, J. C., Zanetti, A., Zeng, Y., Zhang, X., Zheng, Y., and Zucchelli, S.
Subjects: High Energy Physics - Experiment, High Energy Physics - Phenomenology
Abstract: We study the underlying event in proton-antiproton collisions by examining the behavior of charged particles (transverse momentum pT > 0.5 GeV/c, pseudorapidity |\eta| < 1) produced in association with large transverse momentum jets (~2.2 fb-1) or with Drell-Yan lepton-pairs (~2.7 fb-1) in the Z-boson mass region (70 < M(pair) < 110 GeV/c2) as measured by CDF at 1.96 TeV center-of-mass energy. We use the direction of the lepton-pair (in Drell-Yan production) or the leading jet (in high-pT jet production) in each event to define three regions of \eta-\phi space; toward, away, and transverse, where \phi is the azimuthal scattering angle. For Drell-Yan production (excluding the leptons) both the toward and transverse regions are very sensitive to the underlying event. In high-pT jet production the transverse region is very sensitive to the underlying event and is separated into a MAX and MIN transverse region, which helps separate the hard component (initial and final-state radiation) from the beam-beam remnant and multiple parton interaction components of the scattering. The data are corrected to the particle level to remove detector effects and are then compared with several QCD Monte-Carlo models. The goal of this analysis is to provide data that can be used to test and improve the QCD Monte-Carlo models of the underlying event that are used to simulate hadron-hadron collisions., Comment: Submitted to Phys.Rev.D
Published: 2010
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75. Observations of the shell-type SNR Cassiopeia A at TeV energies with VERITAS

Author: The VERITAS Collaboration, Acciari, V. A., Aliu, E., Arlen, T., Aune, T., Bautista, M., Beilicke, M., Benbow, W., Boltuch, D., Bradbury, S. M., Buckley, J. H., Bugaev, V., Butt, Y., Byrum, K., Cannon, A., Cesarini, A., Chow, Y. C., Ciupik, L., Cogan, P., Cui, W., Dickherber, R., Duke, C., Ergin, T., Fegan, S. J., Finley, J. P., Finnegan, G., Fortin, P., Fortson, L., Furniss, A., Galante, N., Gall, D., Gillanders, G. H., Grube, J., Guenette, R., Gyuk, G., Hanna, D., Holder, J., Huang, D., Hui, C. M., Humensky, T. B., Kaaret, P., Karlsson, N., Kertzman, M., Kieda, D., Konopelko, A., Krawczynski, H., Krennrich, F., Lang, M. J., LeBohec, S., Maier, G., McArthur, S., McCann, A., McCutcheon, M., Millis, J., Moriarty, P., Ong, R. A., Pandel, D., Perkins, J. S., Pohl, M., Quinn, J., Ragan, K., Reynolds, P. T., Roache, E., Rose, H. J., Schroedter, M., Sembroski, G. H., Smith, A. W., Smith, B. R., Steele, D., Swordy, S. P., Theiling, M., Thibadeau, S., Varlotta, A., Vassiliev, V. V., Vincent, S., Wagner, R. G., Wakely, S. P., Ward, J. E., Weekes, T. C., Weinstein, A., Weisgarber, T., Wissel, S., and Wood, M.
Subjects: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Galaxy Astrophysics
Abstract: We report on observations of very high-energy gamma rays from the shell-type supernova remnant Cassiopeia A with the VERITAS stereoscopic array of four imaging atmospheric Cherenkov telescopes in Arizona. The total exposure time for these observations is 22 hours, accumulated between September and November of 2007. The gamma-ray source associated with the SNR Cassiopeia A was detected above 200 GeV with a statistical significance of 8.3 s.d. The estimated integral flux for this gamma-ray source is about 3% of the Crab-Nebula flux. The photon spectrum is compatible with a power law dN/dE ~ E^(-Gamma) with an index Gamma = 2.61 +/- 0.24(stat) +/- 0.2(sys). The data are consistent with a point-like source. We provide a detailed description of the analysis results, and discuss physical mechanisms that may be responsible for the observed gamma-ray emission., Comment: 27 pages, 2 figures; Accepted for publication in ApJ
Published: 2010
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76. Discovery of Variability in the Very High Energy Gamma-Ray Emission of 1ES 1218+304 with VERITAS

Author: The VERITAS Collaboration, Acciari, V. A., Aliu, E., Beilicke, M., Benbow, W., Boltuch, D., Böttcher, M., Bradbury, S. M., Bugaev, V., Byrum, K., Cesarini, A., Ciupik, L., Cogan, P., Cui, W., Dickherber, R., Duke, C., Falcone, A., Finley, J. P., Finnegan, G., Fortson, L., Furniss, A., Galante, N., Gall, D., Gibbs, K., Guenette, R., Gillanders, G. H., Godambe, S., Grube, J., Hanna, D., Hui, C. M., Humensky, T. B., Imran, A., Kaaret, P., Karlsson, N., Kertzman, M., Kieda, D., Krawczynski, H., Krennrich, F., Lang, M. J., LeBohec, S., Maier, G., McArthur, S., McCann, A., Moriarty, P., Nagai, T., Ong, R. A., Otte, A. N., Pandel, D., Perkins, J. S., Pichel, A., Pohl, M., Quinn, J., Ragan, K., Reyes, L. C., Reynolds, P. T., Roache, E., Rose, H. J., Schroedter, M., Sembroski, G. H., Smith, A. W., Steele, D., Swordy, S. P., Theiling, M., Thibadeau, S., Vassiliev, V. V., Vincent, S., Wakely, S. P., Weekes, T. C., Weinstein, A., Weisgarber, T., and Williams, D. A.
Subjects: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Cosmology and Extragalactic Astrophysics
Abstract: We present results from an intensive VERITAS monitoring campaign of the high-frequency peaked BL Lac object 1ES 1218+304 in 2008/2009. Although 1ES 1218+304 was detected previously by MAGIC and VERITAS at a persistent level of ~6% of the Crab Nebula flux, the new VERITAS data reveal a prominent flare reaching ~20% of the Crab. While very high energy (VHE) flares are quite common in many nearby blazars, the case of 1ES 1218+304 (redshift z = 0.182) is particularly interesting since it belongs to a group of blazars that exhibit unusually hard VHE spectra considering their redshifts. When correcting the measured spectra for absorption by the extragalactic background light, 1ES 1218+304 and a number of other blazars are found to have differential photon indices less than 1.5. The difficulty in modeling these hard spectral energy distributions in blazar jets has led to a range of theoretical gamma-ray emission scenarios, one of which is strongly constrained by these new VERITAS observations. We consider the implications of the observed light curve of 1ES 1218+304, which shows day scale flux variations, for shock acceleration scenarios in relativistic jets, and in particular for the viability of kiloparsec-scale jet emission scenarios., Comment: 5 pages, 3 figures; Published in The Astrophysical Journal Letters
Published: 2010
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77. Highlight Talk: Recent Results from VERITAS

Author: Ong, R. A., Acciari, V. A., Arlen, T., Aune, T., Beilicke, M., Benbow, W., Boltuch, D., Bradbury, S. M., Buckley, J. H., Bugaev, V., Byrum, K., Cannon, A., Cesarini, A., Ciupik, L., Chow, Y. C., Cogan, P., Cui, W., Duke, C., Fegan, S. J., Finley, J. P., Finnegan, G., Fortin, P., Fortson, L., Furniss, A., Galante, N., Gall, D., Gillanders, G. H., Godambe, S., Grube, J., Guenette, R., Gyuk, G., Hanna, D., Holder, J., Horan, D., Hui, C. M., Humensky, T. B., Imran, A., Kaaret, P., Karlsson, N., Kertzman, M., Kieda, D., Konopelko, A., Krawczynski, H., Krennrich, F., Lang, M. J., Maier, G., McArthur, S., McCann, A., McCutcheon, M., Millis, J., Moriarty, P., Otte, A. N., Pandel, D., Perkins, J. S., Pichel, A., Pohl, M., Quinn, J., Ragan, K., Reyes, L. C., Reynolds, P. T., Roache, E., Rose, H. J., Schroedter, M., Sembroski, G. H., Smith, A. W., Steele, D., Swordy, S. P., Theiling, M., Thibadeau, S., Toner, J. A., Varlotta, A., Vassiliev, V. V., Vincent, S., Wagner, R. G., Wakely, S. P., Ward, J. E., Weekes, T. C., Weinstein, A., Williams, D. A., Wissel, S., Wood, M., and Zitzer, B.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: VERITAS is a state-of-the-art ground-based gamma-ray observatory that operates in the very high-energy (VHE) region of 100 GeV to 50 TeV. The observatory consists of an array of four 12m-diameter imaging atmospheric Cherenkov telescopes located in southern Arizona, USA. The four-telescope array has been fully operational since September 2007, and over the last two years, VERITAS has been operating with high efficiency and with excellent performance. This talk summarizes the recent results from VERITAS, including the discovery of eight new VHE gamma-ray sources., Comment: Highlight Talk at 31st Int. Cosmic Ray Conference (Lodz 2009). 9 pages and 8 figures. (Fixed rotation of figures)
Published: 2009

78. Detection of Extended VHE Gamma Ray Emission from G106.3+2.7 with VERITAS

Author: VERITAS Collaboration, Acciari, V. A., Aliu, E., Arlen, T., Aune, T., Bautista, M., Beilicke, M., Benbow, W., Boltuch, D., Bradbury, S. M., Buckley, J. H., Bugaev, V., Butt, Y., Byrum, K., Cannon, A., Cesarini, A., Chow, Y. C., Ciupik, L., Cogan, P., Cui, W., Dickherber, R., Ergin, T., Fegan, S. J., Finley, J. P., Fortin, P., Fortson, L., Furniss, A., Gall, D., Gillanders, G. H., Gotthelf, E. V., Grube, J., Guenette, R., Gyuk, G., Hanna, D., Holder, J., Horan, D., Hui, C. M., Humensky, T. B., Kaaret, P., Karlsson, N., Kertzman, M., Kieda, D., Konopelko, A., Krawczynski, H., Krennrich, F., Lang, M. J., LeBohec, S., Maier, G., McCann, A., McCutcheon, M., Millis, J., Moriarty, P., Mukherjee, R., Ong, R. A., Otte, A. N., Pandel, D., Perkins, J. S., Pohl, M., Quinn, J., Ragan, K., Reyes, L. C., Reynolds, P. T., Roache, E., Rose, H. J., Schroedter, M., Sembroski, G. H., Smith, A. W., Steele, D., Swordy, S. P., Theiling, M., Toner, J. A., Vassiliev, V. V., Vincent, S., Wagner, R. G., Wakely, S. P., Ward, J. E., Weekes, T. C., Weinstein, A., Weisgarber, T., Williams, D. A., Wissel, S., Wood, M., and Zitzer, B.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: We report the detection of very-high-energy (VHE) gamma-ray emission from supernova remnant (SNR) G106.3+2.7. Observations performed in 2008 with the VERITAS atmospheric Cherenkov gamma-ray telescope resolve extended emission overlapping the elongated radio SNR. The 7.3 sigma (pre-trials) detection has a full angular extent of roughly 0.6deg by 0.4deg. Most notably, the centroid of the VHE emission is centered near the peak of the coincident 12CO (J = 1-0) emission, 0.4deg away from the pulsar PSR J2229+6114, situated at the northern end of the SNR. Evidently the current-epoch particles from the pulsar wind nebula are not participating in the gamma-ray production. The VHE energy spectrum measured with VERITAS is well characterized by a power law dN/dE = N_0(E/3 TeV)^{-G} with a differential index of G = 2.29 +/- 0.33stat +/- 0.30sys and a flux of N_0 = (1.15 +/- 0.27stat +/- 0.35sys)x 10^{-13} cm^{-2} s^{-1} TeV^{-1}. The integral flux above 1 TeV corresponds to ~5 percent of the steady Crab Nebula emission above the same energy. We describe the observations and analysis of the object and briefly discuss the implications of the detection in a multiwavelength context., Comment: 5 pages, 2 figures
Published: 2009
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79. A connection between star formation activity and cosmic rays in the starburst galaxy M 82

Author: Acciari, V. A., Aliu, E., Arlen, T., Aune, T., Bautista, M., Beilicke, M., Benbow, W., Boltuch, D., Bradbury, S. M., Buckley, J. H., Bugaev, V., Byrum, K., Cannon, A., Celik, O., Cesarini, A., Chow, Y. C., Ciupik, L., Cogan, P., Colin, P., Cui, W., Dickherber, R., Duke, C., Fegan, S. J., Finley, J. P., Finnegan, G., Fortin, P., Fortson, L., Furniss, A., Galante, N., Gall, D., Gibbs, K., Gillanders, G. H., Godambe, S., Grube, J., Guenette, R., Gyuk, G., Hanna, D., Holder, J., Horan, D., Hui, C. M., Humensky, T. B., Imran, A., Kaaret, P., Karlsson, N., Kertzman, M., Kieda, D., Kildea, J., Konopelko, A., Krawczynski, H., Krennrich, F., Lang, M. J., LeBohec, S., Maier, G., McArthur, S., McCann, A., McCutcheon, M., Millis, J., Moriarty, P., Mukherjee, R., Nagai, T., Ong, R. A., Otte, A. N., Pandel, D., Perkins, J. S., Pizlo, F., Pohl, M., Quinn, J., Ragan, K., Reyes, L. C., Reynolds, P. T., Roache, E., Rose, H. J., Schroedter, M., Sembroski, G. H., Smith, A. W., Steele, D., Swordy, S. P., Theiling, M., Thibadeau, S., Varlotta, A., Vassiliev, V. V., Vincent, S., Wagner, R. G., Wakely, S. P., Ward, J. E., Weekes, T. C., Weinstein, A., Weisgarber, T., Williams, D. A., Wissel, S., Wood, M., and Zitzer, B.
Subjects: Astrophysics - Cosmology and Extragalactic Astrophysics
Abstract: Although Galactic cosmic rays (protons and nuclei) are widely believed to be dominantly accelerated by the winds and supernovae of massive stars, definitive evidence of this origin remains elusive nearly a century after their discovery [1]. The active regions of starburst galaxies have exceptionally high rates of star formation, and their large size, more than 50 times the diameter of similar Galactic regions, uniquely enables reliable calorimetric measurements of their potentially high cosmic-ray density [2]. The cosmic rays produced in the formation, life, and death of their massive stars are expected to eventually produce diffuse gamma-ray emission via their interactions with interstellar gas and radiation. M 82, the prototype small starburst galaxy, is predicted to be the brightest starburst galaxy in gamma rays [3, 4]. Here we report the detection of >700 GeV gamma rays from M 82. From these data we determine a cosmic-ray density of 250 eV cm-3 in the starburst core of M 82, or about 500 times the average Galactic density. This result strongly supports that cosmic-ray acceleration is tied to star formation activity, and that supernovae and massive-star winds are the dominant accelerators., Comment: 18 pages, 4 figures; published in Nature; Version is prior to Nature's in-house style editing (differences are minimal)
Published: 2009
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80. VERITAS Upper Limit on the VHE Emission from the Radio Galaxy NGC 1275

Author: VERITAS Collaboration, Acciari, V. A., Aliu, E., Arlen, T., Aune, T., Bautista, M., Beilicke, M., Benbow, W., Boltuch, D., Bradbury, S. M., Buckley, J. H., Bugaev, V., Byrum, K., Cannon, A., Celik, O., Cesarini, A., Ciupik, L., Cogan, P., Cui, W., Dickherber, R., Duke, C., Fegan, S. J., Finley, J. P., Fortin, P., Fortson, L., Furniss, A., Galante, N., Gall, D., Gibbs, K., Gillanders, G. H., Godambe, S., Grube, J., Guenette, R., Gyuk, G., Hanna, D., Holder, J., Horan, D., Hui, C. M., Humensky, T. B., Imran, A., Kaaret, P., Karlsson, N., Kertzman, M., Kieda, D., Konopelko, A., Krawczynski, H., Krennrich, F., Lang, M. J., LeBohec, S., Maier, G., McCann, A., McCutcheon, M., Millis, J., Moriarty, P., Mukherjee, R., Ong, R. A., Otte, A. N., Pandel, D., Perkins, J. S., Pohl, M., Quinn, J., Ragan, K., Reynolds, P. T., Roache, E., Rose, H. J., Schroedter, M., Sembroski, G. H., Smith, A. W., Steele, D., Swordy, S. P., Theiling, M., Toner, J. A., Varlotta, A., Vassiliev, V. V., Vincent, S., Wagner, R. G., Wakely, S. P., Ward, J. E., Weekes, T. C., Weinstein, A., Weisgarber, T., Williams, D. A., Wissel, S., Wood, M., Zitzer, B., Kataoka, J., Cavazzuti, E., Cheung, C. C., Lott, B., Thompson, D. J., and Tosti, G.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: The recent detection by the Fermi gamma-ray space telescope of high-energy gamma-rays from the radio galaxy NGC 1275 makes the observation of the very high energy (VHE: E > 100 GeV) part of its broadband spectrum particularly interesting, especially for the understanding of active galactic nuclei (AGN) with misaligned multi-structured jets. The radio galaxy NGC 1275 was recently observed by VERITAS at energies above 100 GeV for about 8 hours. No VHE gamma-ray emission was detected by VERITAS from NGC 1275. A 99% confidence level upper limit of 2.1% of the Crab Nebula flux level is obtained at the decorrelation energy of approximately 340 GeV, corresponding to 19% of the power-law extrapolation of the Fermi Large Area Telescope (LAT) result., Comment: Accepted for publication in ApJ Letters
Published: 2009
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81. Multiwavelength observations of a TeV-Flare from W Comae

Author: VERITAS collaboration, Acciari, V. A., Aliu, E., Aune, T., Beilicke, M., Benbow, W., Bottcher, M., Boltuch, D., Buckley, J. H., Bradbury, S. M., Bugaev, V., Byrum, K., Cannon, A., Cesarini, A., Ciupik, L., Cogan, P., Cui, W., Dickherber, R., Duke, C., Falcone, A., Finley, J. P., Fortin, P., Fortson, L., Furniss, A., Galante, N., Gall, D., Gibbs, K., Gillanders, G. H., Grube, J., Guenette, R., Gyuk, G., Hanna, D., Holder, J., Hui, C. M., Humensky, T. B., Kaaret, P., Karlsson, N., Kertzman, M., Kieda, D., Konopelko, A., Krawczynski, H., Krennrich, F., Lang, M. J., LeBohec, S., Maier, G., McArthur, S., McCann, A., McCutcheon, M., Millis, J., Moriarty, P., Ong, R. A., Otte, A. N., Pandel, D., Perkins, J. S., Pichel, A., Pohl, M., Quinn, J., Ragan, K., Reyes, L. C., Reynolds, P. T., Roache, E., Rose, H. J., Sembroski, G. H., Smith, A. W., Steele, D., Theiling, M., Thibadeau, S., Varlotta, A., Vassiliev, V. V., Vincent, S., Wakely, S. P., Ward, J. E., Weekes, T. C., Weinstein, A., Weisgarber, T., Williams, D. A., Wissel, S., Wood, M., Team, The AGILE, Pian, E., Vercellone, S., Donnarumma, I., D'Ammando, F., Bulgarelli, A., Chen, A. W., Giuliani, A., Longo, F., Pacciani, L., Pucella, G., Vittorini, V., Tavani, M., Argan, A., Barbiellini, G., Caraveo, P., Cattaneo, P. W., Cocco, V., Costa, E., Del Monte, E., De Paris, G., Di Cocco, G., Evangelista, Y., Feroci, M., Fiorini, M., Froysland, T., Frutti, M., Fuschino, F., Galli, M., Gianotti, F., Labanti, C., Lapshov, I., Lazzarotto, F., Lipari, P., Marisaldi, M., Mastropietro, M., Mereghetti, S., Morelli, E., Morselli, A., Pellizzoni, A., Perotti, F., Piano, G., Picozza, P., Pilia, M., Porrovecchio, G., Prest, M., Rapisarda, M., Rappoldi, A., Rubini, A., Soffitta, S. Sabatini P., Trifoglio, M., Trois, A., Vallazza, E., Zambra, A., Zanello, D., Pittori, C., Santolamazza, P., Verrecchia, F., Giommi, P., Colafrancesco, S., Salotti, L., Villata, M., Raiteri, C. M., Aller, H. D., Aller, M. F., Arkharov, A. A., Efimova, N. V., Larionov, V. M., Leto, P., Ligustri, R., Lindfors, E., Pasanen, M., Kurtanidze, O. M., Tetradze, S. D., Lahteenmaki, A., Kotiranta, M., Cucchiara, A., Romano, P., Nesci, R., Pursimo, T., Heidt, J., Benitez, E., Hiriart, D., Nilsson, K., Berdyugin, A., Mujica, R., Dultzin, D., Lopez, J. M., Mommert, M., Sorcia, M., and Perez, I. de la Calle
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: We report results from an intensive multiwavelength campaign on the intermediate-frequency-peaked BL Lacertae object W Com (z=0.102) during a strong outburst of very high energy gamma-ray emission in June 2008. The very high energy gamma-ray signal was detected by VERITAS on 2008 June 7-8 with a flux F(>200 GeV) = (5.7+-0.6)x10^-11 cm-2s-1, about three times brighter than during the discovery of gamma-ray emission from W Com by VERITAS in 2008 March. The initial detection of this flare by VERITAS at energies above 200 GeV was followed by observations in high energy gamma-rays (AGILE, E>100 MeV), and X-rays (Swift and XMM-Newton), and at UV, and ground-based optical and radio monitoring through the GASP-WEBT consortium and other observatories. Here we describe the multiwavelength data and derive the spectral energy distribution (SED) of the source from contemporaneous data taken throughout the flare., Comment: 26 pages, 5 figures; Accepted for publication by The Astrophysical Journal
Published: 2009
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82. A Topological Trigger System for Imaging Atmospheric-Cherenkov Telescopes

Author: Schroedter, M., Anderson, J., Byrum, K., Drake, G., Duke, C., Holder, J., Imran, A., Madhavan, A., Krennrich, F., Kreps, A., and Smith, A.
Subjects: Astrophysics - Instrumentation and Methods for Astrophysics
Abstract: A fast trigger system is being designed as a potential upgrade to VERITAS, or as the basis for a future array of imaging atmospheric-Cherenkov telescopes such as AGIS. The scientific goal is a reduction of the energy threshold by a factor of 2 over the current threshold of VERITAS of around 130 GeV. The trigger is being designed to suppress both accidentals from the night-sky background and cosmic rays. The trigger uses field-programmable gate arrays (FPGAs) so that it is adaptable to different observing modes and special physics triggers, e.g. pulsars. The trigger consists of three levels: The level 1 (L1.5) trigger operating on each telescope camera samples the discriminated pixels at a rate of 400 MHz and searches for nearest-neighbor coincidences. In L1.5, the received discriminated signals are delay-compensated with an accuracy of 0.078 ns, facilitating a short coincidence time-window between any nearest neighbor of 5 ns. The hit pixels are then sent to a second trigger level (L2) that parameterizes the image shape and transmits this information along with a GPS time stamp to the array-level trigger (L3) at a rate of 10 MHz via a fiber optic link. The FPGA-based event analysis on L3 searches for coincident time-stamps from multiple telescopes and carries out a comparison of the image parameters against a look-up table at a rate of 10 kHz. A test of the single-telescope trigger was carried out in spring 2009 on one VERITAS telescope., Comment: 4 pages, 6 figures, to be published in Proceedings of the 31st International Cosmic Ray Conference (ICRC), Lodz, Poland, July 2009
Published: 2009

83. Observation of Extended VHE Emission from the Supernova Remnant IC 443 with VERITAS

Author: VERITAS Collaboration, Acciari, V. A., Aliu, E., Arlen, T., Aune, T., Bautista, M., Beilicke, M., Benbow, W., Bradbury, S. M., Buckley, J. H., Bugaev, V., Butt, Y., Byrum, K., Cannon, A., Celik, O., Cesarini, A., Chow, Y. C., Ciupik, L., Cogan, P., Colin, P., Cui, W., Daniel, M. K., Dickherber, R., Duke, C., Dwarkadas, V. V., Ergin, T., Fegan, S. J., Finley, J. P., Finnegan, G., Fortin, P., Fortson, L., Furniss, A., Gall, D., Gibbs, K., Gillanders, G. H., Godambe, S., Grube, J., Guenette, R., Gyuk, G., Hanna, D., Hays, E., Holder, J., Horan, D., Hui, C. M., Humensky, T. B., Imran, A., Kaaret, P., Karlsson, N., Kertzman, M., Kieda, D., Kildea, J., Konopelko, A., Krawczynski, H., Krennrich, F., Lang, M. J., LeBohec, S., Maier, G., McCann, A., McCutcheon, M., Millis, J., Moriarty, P., Ong, R. A., Otte, A. N., Pandel, D., Perkins, J. S., Pohl, M., Quinn, J., Ragan, K., Reyes, L. C., Reynolds, P. T., Roache, E., Rose, H. J., Schroedter, M., Sembroski, G. H., Smith, A. W., Steele, D., Swordy, S. P., Theiling, M., Toner, J. A., Valcarcel, L., Varlotta, A., Vassiliev, V. V., Vincent, S., Wagner, R. G., Wakely, S. P., Ward, J. E., Weekes, T. C., Weinstein, A., Weisgarber, T., Williams, D. A., Wissel, S., Wood, M., and Zitzer, B.
Subjects: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Galaxy Astrophysics
Abstract: We present evidence that the very-high-energy (VHE, E > 100 GeV) gamma-ray emission coincident with the supernova remnant IC 443 is extended. IC 443 contains one of the best-studied sites of supernova remnant/molecular cloud interaction and the pulsar wind nebula CXOU J061705.3+222127, both of which are important targets for VHE observations. VERITAS observed IC 443 for 37.9 hours during 2007 and detected emission above 300 GeV with an excess of 247 events, resulting in a significance of 8.3 standard deviations (sigma) before trials and 7.5 sigma after trials in a point-source search. The emission is centered at 06 16 51 +22 30 11 (J2000) +- 0.03_stat +- 0.08_sys degrees, with an intrinsic extension of 0.16 +- 0.03_stat +- 0.04_sys degrees. The VHE spectrum is well fit by a power law (dN/dE = N_0 * (E/TeV)^-Gamma) with a photon index of 2.99 +- 0.38_stat +- 0.3_sys and an integral flux above 300 GeV of (4.63 +- 0.90_stat +- 0.93_sys) * 10^-12 cm^-2 s^-1. These results are discussed in the context of existing models for gamma-ray production in IC 443., Comment: 7 pages, accepted by ApJL
Published: 2009
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84. Evidence for long-term Gamma-ray and X-ray variability from the unidentified TeV source HESS J0632+057

Author: VERITAS Collaboration, Acciari, V. A., Aliu, E., Arlen, T., Beilicke, M., Benbow, W., Boltuch, D., Bradbury, S. M., Buckley, J. H., Bugaev, V., Byrum, K., Cannon, A., Cesarini, A., Chow, Y. C., Ciupik, L., Cogan, P., Dickherber, R., Duke, C., Ergin, T., Falcone, A., Fegan, S. J., Finley, J. P., Finnegan, G., Fortin, P., Fortson, L., Furniss, A., Gibbs, K., Gillanders, G. H., Grube, J., Guenette, R., Gyuk, G., Hanna, D., Holder, J., Horan, D., Hui, C. M., Humensky, T. B., Imran, A., Kaaret, P., Karlsson, N., Kertzman, M., Kieda, D., Kildea, J., Konopelko, A., Krawczynski, H., Krennrich, F., Lang, M. J., LeBohec, S., Maier, G., McCann, A., McCutcheon, M., Millis, J., Moriarty, P., Mukherjee, R., Ong, R. A., Otte, A. N., Pandel, D., Perkins, J. S., Petry, D., Pohl, M., Quinn, J., Ragan, K., Reyes, L. C., Reynolds, P. T., Rose, H. J., Schroedter, M., Sembroski, G. H., Smith, A. W., Steele, D., Theiling, M., Toner, J. A., Varlotta, A., Vassiliev, V. V., Vincent, S., Wagner, R. G., Wakely, S. P., Ward, J. E., Weekes, T. C., Weinstein, A., Weisgarber, T., Williams, D. A., Wissel, S., and Wood, M.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: HESS J0632+057 is one of only two unidentified very-high-energy gamma-ray sources which appear to be point-like within experimental resolution. It is possibly associated with the massive Be star MWC 148 and has been suggested to resemble known TeV binary systems like LS I +61 303 or LS 5039. HESS J0632+057 was observed by VERITAS for 31 hours in 2006, 2008 and 2009. During these observations, no significant signal in gamma rays with energies above 1 TeV was detected from the direction of HESS J0632+057. A flux upper limit corresponding to 1.1% of the flux of the Crab Nebula has been derived from the VERITAS data. The non-detection by VERITAS excludes with a probability of 99.993% that HESS J0632+057 is a steady gamma-ray emitter. Contemporaneous X-ray observations with Swift XRT reveal a factor of 1.8+-0.4 higher flux in the 1-10 keV range than earlier X-ray observations of HESS J0632+057. The variability in the gamma-ray and X-ray fluxes supports interpretation of the ob ject as a gamma-ray emitting binary., Comment: 8 pages, 3 figures, Accepted for publication in The Astrophysical Journal
Published: 2009
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85. VERITAS Observations of a Very High Energy Gamma-ray Flare from the Blazar 3C 66A

Author: VERITAS Collaboration, Acciari, V. A., Aliu, E., Arlen, T., Beilicke, M., Benbow, W., Bottcher, M., Bradbury, S. M., Buckley, J. H., Bugaev, V., Butt, Y., Byrum, K., Cannon, A., Celik, O., Cesarini, A., Chow, Y. C., Ciupik, L., Cogan, P., Cui, W., Daniel, M. K., Dickherber, R., Ergin, T., Falcone, A., Fegan, S. J., Finley, J. P., Fortin, P., Fortson, L., Furniss, A., Gall, D., Gibbs, K., Gillanders, G. H., Godambe, S., Grube, J., Guenette, R., Gyuk, G., Hanna, D., Hays, E., Holder, J., Horan, D., Hui, C. M., Humensky, T. B., Imran, A., Kaaret, P., Karlsson, N., Kertzman, M., Kieda, D., Kildea, J., Konopelko, A., Krawczynski, H., Krennrich, F., Lang, M. J., LeBohec, S., Maier, G., McCann, A., McCutcheon, M., Millis, J., Moriarty, P., Mukherjee, R., Nagai, T., Ong, R. A., Otte, A. N., Pandel, D., Perkins, J. S., Petry, D., Pizlo, F., Pohl, M., Quinn, J., Ragan, K., Reyes, L. C., Reynolds, P. T., Roache, E., Rose, H. J., Schroedter, M., Sembroski, G. H., Smith, A. W., Steele, D., Swordy, S. P., Theiling, M., Toner, J. A., Varlotta, A., Vassiliev, V. V., Wagner, R. G., Wakely, S. P., Ward, J. E., Weekes, T. C., Weinstein, A., Williams, D. A., Wissel, S., Wood, M., and Zitzer, B.
Subjects: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Cosmology and Extragalactic Astrophysics
Abstract: The intermediate-frequency peaked BL Lacertae (IBL) object 3C 66A is detected during 2007 - 2008 in VHE (very high energy: E > 100 GeV) gamma-rays with the VERITAS stereoscopic array of imaging atmospheric Cherenkov telescopes. An excess of 1791 events is detected, corresponding to a significance of 21.2 standard deviations (sigma), in these observations (32.8 hours live time). The observed integral flux above 200 GeV is 6% of the Crab Nebula's flux and shows evidence for variability on the time-scale of days. The measured energy spectrum is characterized by a soft power law with photon index Gamma = 4.1 +- 0.4_stat +- 0.6_sys. The radio galaxy 3C 66B is excluded as a possible source of the VHE emission., Comment: 13 Pages, 4 Figures. Published in ApJL. This new version correctly calculates the intrinsic photon index (see Erratum: ApJL, 721:L203-L204)
Published: 2009
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86. VERITAS observations of the BL Lac 1ES 1218+304

Author: VERITAS Collaboration, Acciari, V. A., Aliu, E., Arlen, T., Beilicke, M., Benbow, W., Bradbury, S. M., Buckley, J. H., Bugaev, V., Butt, Y., Byrum, K. L., Celik, O., Cesarini, A., Ciupik, L., Chow, Y. C. K., Cogan, P., Colin, P., Cui, W., Daniel, M. K., Ergin, T., Falcone, A. D., Fegan, S. J., Finley, J. P., Fortin, P., Fortson, L. F., Furniss, A., Gillanders, G. H., Grube, J., Guenette, R., Gyuk, G., Hanna, D., Hays, E., Holder, J., Horan, D., Hui, C. M., Humensky, T. B., Imran, A., Kaaret, P., Karlsson, N., Kertzman, M., Kieda, D. B., Kildea, J., Konopelko, A., Krawczynski, H., Krennrich, F., Lang, M. J., LeBohec, S., Maier, G., McCann, A., McCutcheon, M., Moriarty, P., Mukherjee, R., Nagai, T., Niemiec, J., Ong, R. A., Pandel, D., Perkins, J. S., Pohl, M., Quinn, J., Ragan, K., Reyes, L. C., Reynolds, P. T., Rose, H. J., Schroedter, M., Sembroski, G. H., Smith, A. W., Steele, D., Swordy, S. P., Toner, J. A., Valcarcel, L., Vassiliev, V. V., Wagner, R., Wakely, S. P., Ward, J. E., Weekes, T. C., Weinstein, A., White, R. J., Williams, D. A., Wissel, S. A., Wood, M., and Zitzer, B.
Subjects: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Cosmology and Nongalactic Astrophysics
Abstract: The VERITAS collaboration reports the detection of very-high-energy (VHE) gamma-ray emission from the high-frequency-peaked BL Lac object 1ES 1218+304 located at a redshift of z=0.182. A gamma-ray signal was detected with a statistical significance of 10.4 standard deviations (10.4 sigma) for the observations taken during the first three months of 2007, confirming the discovery of this object made by the MAGIC collaboration. The photon spectrum between ~160 GeV and ~1.8 TeV is well described by a power law with an index of Gamma = 3.08 +/- 0.34_stat +/- 0.2_sys. The integral flux is Phi(E > 200 GeV) = (12.2 +/- 2.6) X 10^-12 cm^-2 s^-1, which corresponds to ~6% of that of the Crab Nebula. The light curve does not show any evidence for VHE flux variability. Using lower limits on the density of the extragalactic background light in the near to mid-infrared we are able to limit the range of intrinsic energy spectra for 1ES 1218+304. We show that the intrinsic photon spectrum has an index that is harder than Gamma = 2.32 +/- 0.37_stat. When including constraints from the spectra of 1ES 1101-232 and 1ES 0229+200, the spectrum of 1ES 1218+304 is likely to be harder than Gamma = 1.86 +/- 0.37_stat., Comment: Accepted for publication in The Astrophysical Journal
Published: 2009
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87. Multiwavelength Observations of Markarian 421 in 2005 - 2006

Author: Horan, D., Acciari, V. A., Bradbury, S. M., Buckley, J. H., Bugaev, V., Byrum, K. L., Cannon, A., Celik, O., Cesarini, A., Chow, Y. C. K., Ciupik, L., Cogan, P., Falcone, A. D., Fegan, S. J., Finley, J. P., Fortin, P., Fortson, L. F., Gall, D., Gillanders, G. H., Grube, J., Gyuk, G., Hanna, D., Hays, E., Kertzman, M., Kildea, J., Konopelko, A., Krawczynski, H., Lang, M. J., Lee, K., Moriarty, P., Nagai, T., Niemiec, J., Ong, R. A., Perkins, J. S., Pohl, M., Quinn, J., Reynolds, P. T., Rose, H. J., Sembroski, G. H., Smith, A. W., Steele, D., Swordy, S. P., Toner, J. A., Vassiliev, V. V., Wakely, S. P., Weekes, T. C., White, R. J., Williams, D. A., Wood, M. D., Zitzer, B., Aller, H. D., Aller, M. F., Baker, M., Barnaby, D., Carini, M. T., Charlot, P., Dumm, J. P., Fields, N. E., Hovatta, T., Jordan, B., Kovalev, Y. A., Kovalev, Y. Y., Krimm, H. A., Kurtanidze, O. M., Lahteenmaki, A., Campion, J. F. Le, Maune, J., Montaruli, T., Sadun, A. C., Smith, S., Tornikoski, M., Turunen, M., and Walters, R.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: Since September 2005, the Whipple 10m Gamma-ray Telescope has been operated primarily as a blazar monitor. The five Northern Hemisphere blazars that have already been detected at the Whipple Observatory, Markarian 421, H1426+428, Markarian 501, 1ES 1959+650 and 1ES 2344+514, are monitored routinely each night that they are visible. We report on the Markarian 421 observations taken from November 2005 to June 2006 in the gamma-ray, X-ray, optical and radio bands. During this time, Markarian 421 was found to be variable at all wavelengths probed. Both the variability and the correlations among different energy regimes are studied in detail here. A tentative correlation, with large spread, was measured between the X-ray and gamma-ray bands, while no clear correlation was evident among the other energy bands. In addition to this, the well-sampled spectral energy distribution of Markarian 421 (1101+384) is presented for three different activity levels. The observations of the other blazar targets will be reported separately., Comment: 58 pages, 22 Figures. Accepted for publication in ApJ
Published: 2009
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88. DEEP BROADBAND OBSERVATIONS OF THE DISTANT GAMMA-RAY BLAZAR PKS 1424+240

Author: Archambault, S, Aune, T, Behera, B, Beilicke, M, Benbow, W, Berger, K, Bird, R, Biteau, J, Bugaev, V, Byrum, K, Cardenzana, JV, Cerruti, M, Chen, X, Ciupik, L, Connolly, MP, Cui, W, Dumm, J, Errando, M, Falcone, A, Federici, S, Feng, Q, Finley, JP, Fleischhack, H, Fortson, L, Furniss, A, Galante, N, Gillanders, GH, Griffin, S, Griffiths, ST, Grube, J, Gyuk, G, Hanna, D, Holder, J, Hughes, G, Humensky, TB, Johnson, CA, Kaaret, P, Kertzman, M, Khassen, Y, Kieda, D, Krawczynski, H, Krennrich, F, Kumar, S, Lang, MJ, Madhavan, AS, Maier, G, McCann, A, Meagher, K, Moriarty, P, Mukherjee, R, Nieto, D, de Bhróithe, A O'Faoláin, Ong, RA, Otte, AN, Park, N, Pohl, M, Popkow, A, Prokoph, H, Quinn, J, Ragan, K, Rajotte, J, Reyes, LC, Reynolds, PT, Richards, GT, Roache, E, Sembroski, GH, Shahinyan, K, Staszak, D, Telezhinsky, I, Tucci, JV, Tyler, J, Varlotta, A, Vassiliev, VV, Vincent, S, Wakely, SP, Weinstein, A, Welsing, R, Wilhelm, A, Williams, DA, Ackermann, M, Ajello, M, Albert, A, Baldini, L, Bastieri, D, Bellazzini, R, Bissaldi, E, Bregeon, J, Buehler, R, Buson, S, Caliandro, GA, Cameron, RA, Caraveo, PA, Cavazzuti, E, Charles, E, Chiang, J, Ciprini, S, Claus, R, Cutini, S, D'Ammando, F, and de Angelis, A
Subjects: BL Lacertae objects: individual (PKS 1424+240)-cosmic background radiation, gamma rays: galaxies, astro-ph.HE, Astronomical and Space Sciences, Astronomy & Astrophysics
Abstract: We present deep VERITAS observations of the blazar PKS 1424+240, along with contemporaneous Fermi Large Area Telescope, Swift X-ray Telescope, and Swift UV Optical Telescope data between 2009 February 19 and 2013 June 8. This blazar resides at a redshift of z ≥ 0.6035, displaying a significantly attenuated gamma-ray flux above 100 GeV due to photon absorption via pair-production with the extragalactic background light. We present more than 100 hr of VERITAS observations over three years, a multiwavelength light curve, and the contemporaneous spectral energy distributions. The source shows a higher flux of (2.1 ± 0.3) × 10-7 photons m-2 s -1 above 120 GeV in 2009 and 2011 as compared to the flux measured in 2013, corresponding to (1.02 ± 0.08) × 10-7 photons m-2 s-1 above 120 GeV. The measured differential very high energy (VHE; E ≥ 100 GeV) spectral indices are Γ = 3.8 ± 0.3, 4.3 ± 0.6 and 4.5 ± 0.2 in 2009, 2011, and 2013, respectively. No significant spectral change across the observation epochs is detected. We find no evidence for variability at gamma-ray opacities of greater than τ = 2, where it is postulated that any variability would be small and occur on timescales longer than a year if hadronic cosmic-ray interactions with extragalactic photon fields provide a secondary VHE photon flux. The data cannot rule out such variability due to low statistics. © 2014. The American Astronomical Society. All rights reserved..
Published: 2014

89. Planning the Future of U.S. Particle Physics (Snowmass 2013): Chapter 8: Instrumentation Frontier

Author: Demarteau, M, Lipton, R, Nicholson, H, Shipsey, I, Akerib, D, Albayrak-Yetkin, A, Alexander, J, Anderson, J, Artuso, M, Asner, D, Ball, R, Battaglia, M, Bebek, C, Beene, J, Benhammou, Y, Bentefour, E, Bergevin, M, Bernstein, A, Bilki, B, Blucher, E, Bolla, G, Bortoletto, D, Bowden, N, Brooijmans, G, Byrum, K, Cabrera, B, Cancelo, G, Carlstrom, J, Casey, B, Chang, C, Chapman, J, Chen, CH, Childres, I, Christian, D, Convery, M, Corso, W Cooper J, Cumalat, J, Cushman, P, Via, C Da, Dazeley, S, Debbins, P, Deptuch, G, Dhawan, S, Benedetto, V Di, DiGiovene, B, Djurcic, Z, Dye, S, Elagin, A, Estrada, J, Evans, H, Etzion, E, Fast, J, Ferretti, C, Fisher, P, Fleming, B, Francis, K, Friedman, P, Frisch, H, Garcia-Sciveres, M, Gatto, C, Geronim, G, Gilchriese, G, Golwala, S, Grant, C, Grillo, A, Grünendahl, E, Gorham, P, Guan, L, Gutierrez, G, Haber, C, Hall, J, Haller, G, Hast, C, Heintz, U, Hemmick, T, Hitlin, DG, Hogan, C, Hohlmann, M, Hoppe, E, Hsu, L, Huffer, M, Irwin, K, Izraelevitch, F, Jennings, G, Johnson, M, Jung, A, Kagan, H, Kenney, C, Kettell, S, Khanna, R, Khristenko, V, Krennrich, F, Kuehn, K, Kutschke, R, Learned, J, Lee, AT, Levin, D, Liu, T, Liu, ATK, and Lissauer, D
Subjects: hep-ex, hep-ph, physics.ins-det
Abstract: These reports present the results of the 2013 Community Summer Study of theAPS Division of Particles and Fields ("Snowmass 2013") on the future program ofparticle physics in the U.S. Chapter 8, on the Instrumentation Frontier,discusses the instrumentation needs of future experiments in the Energy,Intensity, and Cosmic Frontiers, promising new technologies for particlephysics research, and issues of gathering resources for long-term research inthis area.
Published: 2014

90. Discovery of Very High-Energy Gamma-Ray Radiation from the BL Lac 1ES 0806+524

Author: VERITAS Collaboration, Acciari, V., Aliu, E., Arlen, T., Bautista, M., Beilicke, M., Benbow, W., Böttcher, M., Bradbury, S. M., Buckley, J. H., Bugaev, V., Butt, Y., Byrum, K., Cannon, A., Celik, O., Cesarini, A., Chow, Y. C., Ciupik, L., Cogan, P., Colin, P., Cui, W., Dickherber, R., Duke, C., Ergin, T., Falcone, A., Fegan, S. J., Finley, J. P., Finnegan, G., Fortin, P., Fortson, L., Furniss, A., Gall, D., Gibbs, K., Gillanders, G. H., Grube, J., Guenette, R., Gyuk, G., Hanna, D., Hays, E., Holder, J., Horan, D., Hui, C. M., Humensky, T. B., Imran, A., Kaaret, P., Karlsson, N., Kertzman, M., Kieda, D., Kildea, J., Konopelko, A., Krawczynski, H., Krennrich, F., Lang, M. J., LeBohec, S., Maier, G., McCann, A., McCutcheon, M., Millis, J., Moriarty, P., Mukherjee, R., Nagai, T., Ong, R. A., Otte, A. N., Pandel, D., Perkins, J. S., Petry, D., Pohl, M., Quinn, J., Ragan, K., Reyes, L. C., Reynolds, P. T., Roache, E., Rose, J., Schroedter, M., Sembroski, G. H., Smith, A. W., Steele, D., Swordy, S. P., Theiling, M., Toner, J. A., Valcarcel, L., Varlotta, A., Vassiliev, V. V., Wagner, R. G., Wakely, S. P., Ward, J. E., Weekes, T. C., Weinstein, A., White, R. J., Williams, D. A., Wissel, S., Wood, M., and Zitzer, B.
Subjects: Astrophysics
Abstract: The high-frequency-peaked BL-Lacertae object \objectname{1ES 0806+524}, at redshift z=0.138, was observed in the very-high-energy (VHE) gamma-ray regime by VERITAS between November 2006 and April 2008. These data encompass the two-, and three-telescope commissioning phases, as well as observations with the full four-telescope array. \objectname{1ES 0806+524} is detected with a statistical significance of 6.3 standard deviations from 245 excess events. Little or no measurable variability on monthly time scales is found. The photon spectrum for the period November 2007 to April 2008 can be characterized by a power law with photon index $3.6 \pm 1.0_{\mathrm{stat}} \pm 0.3_{\mathrm{sys}}$ between $\sim$300 GeV and $\sim$700 GeV. The integral flux above 300 GeV is $(2.2\pm0.5_{\mathrm{stat}}\pm0.4_{\mathrm{sys}})\times10^{-12}\:\mathrm{cm}^{2}\:\mathrm{s}^{-1}$ which corresponds to 1.8% of the Crab Nebula flux. Non contemporaneous multiwavelength observations are combined with the VHE data to produce a broadband spectral energy distribution that can be reasonably described using a synchrotron-self Compton model., Comment: 14 pages, 4 figures, accepted to APJL
Published: 2008
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91. Section on Prospects for Dark Matter Detection of the White Paper on the Status and Future of Ground-Based TeV Gamma-Ray Astronomy

Author: Buckley, J., Baltz, E. A., Bertone, G., Byrum, K., Fegan, S., Ferrer, F., Gondolo, P., Hall, J., Hooper, D., Horan, D., Koushiappas, S., Krawczynski, H., LeBohec, S., Profumo, S., Silk, J., Tait, T., Vassiliev, V., Wagner, R., Wakely, S., Wood, M., and Zaharijas, G.
Subjects: Astrophysics
Abstract: This is a report on the findings of the dark matter science working group for the white paper on the status and future of TeV gamma-ray astronomy. The white paper was commissioned by the American Physical Society, and the full white paper can be found on astro-ph (arXiv:0810.0444). This detailed section discusses the prospects for dark matter detection with future gamma-ray experiments, and the complementarity of gamma-ray measurements with other indirect, direct or accelerator-based searches. We conclude that any comprehensive search for dark matter should include gamma-ray observations, both to identify the dark matter particle (through the charac- teristics of the gamma-ray spectrum) and to measure the distribution of dark matter in galactic halos., Comment: Report from the Dark Matter Science Working group of the APS commissioned White paper on ground-based TeV gamma ray astronomy (19 pages, 9 figures)
Published: 2008

92. Technology Section of the White Paper on the Status and Future of Ground-based TeV Gamma-ray Astronomy

Author: Byrum, K., Buckley, J., Bugayov, S., Dingus, B., Fegan, S., Funk, S., Hays, E., Holder, J., Horan, D., Konopelko, A., Krawczynski, H., Krennrich, F., Lebohec, S., Sinnis, G., Smith, A., Vassiliev, V., and Wakely, S.
Subjects: Astrophysics
Abstract: This is a report on the findings of the technology working group for the white paper on the status and future of TeV gamma-ray astronomy. The white paper is an APS commissioned document, and the overall version has also been released and can be found on astro-ph. This detailed section of the white paper discusses different technology opportunities and the technical feasibility for substantially improving IACTS and ground based particle detectors to achieve an order of magnitude better sensitivity than the instruments employed today as well as their planned upgrades. A technology roadmap for improving IACTS and ground based particle detectors is presented., Comment: 15 pages, 2 tex files, 1 sty file, 7 figures
Published: 2008

93. Status of the VERITAS Observatory

Author: Holder, J., Acciari, V. A., Aliu, E., Arlen, T., Beilicke, M., Benbow, W., Bradbury, S. M., Buckley, J. H., Bugaev, V., Butt, Y., Byrum, K. L., Cannon, A., Celik, O., Cesarini, A., Ciupik, L., Chow, Y. C. K., Cogan, P., Colin, P., Cui, W., Daniel, M. K., Ergin, T., Falcone, A. D., Fegan, S. J., Finley, J. P., Finnegan, G., Fortin, P., Fortson, L. F., Furniss, A., Gillanders, G. H., Grube, J., Guenette, R., Gyuk, G., Hanna, D., Hays, E., Horan, D., Hui, C. M., Humensky, T. B., Imran, A., Kaaret, P., Karlsson, N., Kertzman, M., Kieda, D. B., Kildea, J., Konopelko, A., Krawczynski, H., Krennrich, F., Lang, M. J., LeBohec, S., Maier, G., McCann, A., McCutcheon, M., Moriarty, P., Mukherjee, R., Nagai, T., Niemiec, J., Ong, R. A., Pandel, D., Perkins, J. S., Pohl, M., Quinn, J., Ragan, K., Reyes, L. C., Reynolds, P. T., Rose, H. J., Schroedter, M., Sembroski, G. H., Smith, A. W., Steele, D., Swordy, S. P., Toner, J. A., Valcarcel, L., Vassiliev, V. V., Wagner, R., Wakely, S. P., Ward, J. E., Weekes, T. C., Weinstein, A., White, R. J., Williams, D. A., Wissel, S. A., Wood, M., and Zitzer, B.
Subjects: Astrophysics
Abstract: VERITAS, an Imaging Atmospheric Cherenkov Telescope (IACT) system for gammma-ray astronomy in the GeV-TeV range, has recently completed its first season of observations with a full array of four telescopes. A number of astrophysical gamma-ray sources have been detected, both galactic and extragalactic, including sources previously unknown at TeV energies. We describe the status of the array and some highlight results, and assess the technical performance, sensitivity and shower reconstruction capabilities., Comment: Submitted to Proceedings of "4th Heidelberg International Symposium on High Energy Gamma-Ray Astronomy 2008"
Published: 2008
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94. The Status and future of ground-based TeV gamma-ray astronomy. A White Paper prepared for the Division of Astrophysics of the American Physical Society

Author: Buckley, J., Byrum, K., Dingus, B., Falcone, A., Kaaret, P., Krawzcynski, H., Pohl, M., Vassiliev, V., and Williams, D. A.
Subjects: Astrophysics, High Energy Physics - Experiment
Abstract: In recent years, ground-based TeV gamma-ray observatories have made spectacular discoveries including imaging spectroscopy observations of galactic sources of different classes, and the discovery of rapid gamma-ray flares from radio galaxies and active galactic nuclei containing supermassive black holes. These discoveries, and the fact that gamma-ray astronomy has the potential to map the radiation from dark matter annihilation in our Galaxy and in extragalactic systems, have attracted the attention of the wider scientific community. The Division of Astrophysics of the American Physical Society requested the preparation of a white paper on the status and future of ground-based gamma-ray astronomy to define the science goals of a future observatory, to determine the performance specifications, to identify the areas of necessary technology development, and to lay out a clear path for proceeding beyond the near term. The white paper was written with broad community input, including discussions on several dedicated open meetings, and a number of APS or other conferences. It contains an executive summary, detailed reports from the science working groups, and appendices with supplementary material including the full author lists for the different sections of the white paper and a glossary., Comment: Individual working-group reports are also available at http://cherenkov.physics.iastate.edu/wp/
Published: 2008

95. VERITAS Observations of the gamma-Ray Binary LS I +61 303

Author: Acciari, V. A., Beilicke, M., Blaylock, G., Bradbury, S. M., Buckley, J. H., Bugaev, V., Butt, Y., Byrum, K. L., Celik, O., Cesarini, A., Ciupik, L., Chow, Y. C. K., Cogan, P., Colin, P., Cui, W., Daniel, M. K., Duke, C., Ergin, T., Falcone, A. D., Fegan, S. J., Finley, J. P., Fortin, P., Fortson, L. F., Gall, D., Gibbs, K., Gillanders, G. H., Guenette, J. Grube R., Hanna, D., Hays, E., Holder, J., Horan, D., Hughes, S. B., Hui, C. M., Humensky, T. B., Kaaret, P., Kieda, D. B., Kildea, J., Konopelko, A., Krawczynski, H., Krennrich, F., Lang, M. J., LeBohec, S., Lee, K., Maier, G., McCann, A., McCutcheon, M., Millis, J., Moriarty, P., Mukherjee, R., Nagai, T., Ong, R. A., Pandel, D., Perkins, J. S., Pizlo, F., Pohl, M., Quinn, J., Ragan, K., Reynolds, P. T., Rose, H. J., Schroedter, M., Sembroski, G. H., Smith, A. W., Steele, D., Swordy, S. P., Toner, J. A., Valcarcel, L., Vassiliev, V. V., Wagner, R., Wakely, S. P., Ward, J. E., Weekes, T. C., Weinstein, A., White, R. J., Williams, D. A., Wissel, S. A., Wood, M., and Zitzer, B.
Subjects: Astrophysics
Abstract: LS I +61 303 is one of only a few high-mass X-ray binaries currently detected at high significance in very high energy gamma-rays. The system was observed over several orbital cycles (between September 2006 and February 2007) with the VERITAS array of imaging air-Cherenkov telescopes. A signal of gamma-rays with energies above 300 GeV is found with a statistical significance of 8.4 standard deviations. The detected flux is measured to be strongly variable; the maximum flux is found during most orbital cycles at apastron. The energy spectrum for the period of maximum emission can be characterized by a power law with a photon index of Gamma=2.40+-0.16_stat+-0.2_sys and a flux above 300 GeV corresponding to 15-20% of the flux from the Crab Nebula., Comment: accepted for publication in The Astrophysical Journal
Published: 2008
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96. A Search for Dark Matter Annihilation with the Whipple 10m Telescope

Author: Wood, M., Blaylock, G., Bradbury, S. M., Buckley, J. H., Byrum, K. L., Chow, Y. C. K., Cui, W., Perez, I. de la Calle, Falcone, A. D., Fegan, S. J., Finley, J. P., Grube, J., Hall, J., Hanna, D., Holder, J., Horan, D., Humensky, T. B., Kieda, D. B., Kildea, J., Konopelko, A., Krawczynski, H., Krennrich, F., Lang, M. J., LeBohec, S., Nagai, T., Ong, R. A., Perkins, J. S., Pohl, M., Quinn, J., Rose, H. J., Sembroski, G. H., Vassiliev, V. V., Wagner, R. G., Wakely, S. P., Weekes, T. C., and Weinstein, A.
Subjects: Astrophysics
Abstract: We present observations of the dwarf galaxies Draco and Ursa Minor, the local group galaxies M32 and M33, and the globular cluster M15 conducted with the Whipple 10m gamma-ray telescope to search for the gamma-ray signature of self-annihilating weakly interacting massive particles (WIMPs) which may constitute astrophysical dark matter (DM). We review the motivations for selecting these sources based on their unique astrophysical environments and report the results of the data analysis which produced upper limits on excess rate of gamma rays for each source. We consider models for the DM distribution in each source based on the available observational constraints and discuss possible scenarios for the enhancement of the gamma-ray luminosity. Limits on the thermally averaged product of the total self-annihilation cross section and velocity of the WIMP, <\sigma v>, are derived using conservative estimates for the magnitude of the astrophysical contribution to the gamma-ray flux. Although these limits do not constrain predictions from the currently favored theoretical models of supersymmetry (SUSY), future observations with VERITAS will probe a larger region of the WIMP parameter phase space, <\sigma v> and WIMP particle mass (m_\chi)., Comment: 33 pages, 12 figures, accepted for publication in the Astrophysical Journal
Published: 2008
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97. The TrICE Prototype MAMPT Imaging Camera

Author: Byrum, K., Cunningham, J., Drake, G., Hays, E., Kieda, D., Kovacs, E., Magill, S., Nodulmann, L., Norhtrop, R., Swordy, S., Wagner, R. G., Wakely, S. P., and Wissel, S. A.
Subjects: Astrophysics
Abstract: The Track Imaging Cerenov Experiment (TrICE) is an air Cerenkov prototype telescope designed to use multi-anode photomultiplier to acheive a high angular resolution for measuring cosmic-ray composition at TeV-PeV energies. The TrICE camera, composed of 16 Hamamatsu R8900 16-channel multi-anode photomultiplier tubes, achieves 0.086 degree angular width per pixel over 1.5 degree wide field of view. We present a description of the TrICE camera design, calibration and performance., Comment: 4 pages, 6 figures, ICRC conference paper
Published: 2007

98. White Paper on the Status and Future of Ground-based Gamma-ray Astronomy

Author: Krawczynski, H., Buckley, J., Byrum, K., Dermer, C., Dingus, B., Falcone, A., Kaaret, P., Krennrich, F., Pohl, M., Vassiliev, V., and Williams, D. A.
Subjects: Astrophysics
Abstract: In recent years, ground-based gamma-ray observatories have made a number of important astrophysical discoveries which have attracted the attention of the wider scientific community. The Division of Astrophysics of the American Physical Society has requested the preparation of a white paper on the status and future of ground-based gamma-ray astronomy to define the science goals of the future observatory, to determine the performance specifications, and to identify the areas of necessary technology development. In this contribution we give a brief overview of the activities of the current white paper team and invite the international community to contribute to the white paper., Comment: 4 pages, Proceedings of the 30th ICRC, Merida, Mexico, July 2007
Published: 2007

99. Very High Energy Observations of Gamma-Ray Burst Locations with the Whipple Telescope

Author: Horan, D., Atkins, R. W., Badran, H. M., Blaylock, G., Bradbury, S. M., Buckley, J. H., Byrum, K. L., Celik, O., Chow, Y. C. K., Cogan, P., Cui, W., Daniel, M. K., Perez, I. de la Calle, Dowdall, C., Falcone, A. D., Fegan, D. J., Fegan, S. J., Finley, J. P., Fortin, P., Fortson, L. F., Gillanders, G. H., Grube, J., Gutierrez, K. J., Hall, J., Hanna, D., Holder, J., Hughes, S. B., Humensky, T. B., Kenny, G. E., Kertzman, M., Kieda, D. B., Kildea, J., Krawczynski, H., Krennrich, F., Lang, M. J., LeBohec, S., Maier, G., Moriarty, P., Nagai, T., Ong, R. A., Perkins, J. S., Petry, D., Quinn, J., Quinn, M., Ragan, K., Reynolds, P. T., Rose, H. J., Schroedter, M., Sembroski, G. H., Steele, D., Swordy, S. P., Toner, J. A., Valcarcel, L., Vassiliev, V. V., Wagner, R. G., Wakely, S. P., Weekes, T. C., White, R. J., and Williams, D. A.
Subjects: Astrophysics
Abstract: Gamma-ray burst (GRB) observations at very high energies (VHE, E > 100 GeV) can impose tight constraints on some GRB emission models. Many GRB afterglow models predict a VHE component similar to that seen in blazars and plerions, in which the GRB spectral energy distribution has a double-peaked shape extending into the VHE regime. VHE emission coincident with delayed X-ray flare emission has also been predicted. GRB follow-up observations have had high priority in the observing program at the Whipple 10m Gamma-ray Telescope and GRBs will continue to be high priority targets as the next generation observatory, VERITAS, comes on-line. Upper limits on the VHE emission, at late times (>~4 hours), from seven GRBs observed with the Whipple Telescope are reported here., Comment: Accepted for publication in the January 20, 2007 volume of the Astrophysical Journal, 655, 396
Published: 2007
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100. The First VERITAS Telescope

Author: Holder, J., Atkins, R. W., Badran, H. M., Blaylock, G., Bradbury, S. M., Buckley, J. H., Byrum, K. L., Carter-Lewis, D. A., Celik, O., Chow, Y. C. K., Cogan, P., Cui, W., Daniel, M. K., Perez, I. de la Calle, Dowdall, C., Dowkontt, P., Duke, C., Falcone, A. D., Fegan, S. J., Finley, J. P., Fortin, P., Fortson, L. F., Gibbs, K., Gillanders, G., Glidewell, O. J., Grube, J., Gutierrez, K. J., Gyuk, G., Hall, J., Hanna, D., Hays, E., Horan, D., Hughes, S. B., Humensky, T. B., Imran, A., Jung, I., Kaaret, P., Kenny, G. E., Kieda, D., Kildea, J., Knapp, J., Krawczynski, H., Krennrich, F., Lang, M. J., LeBohec, S., Linton, E., Little, E. K., Maier, G., Manseri, H., Milovanovic, A., Moriarty, P., Mukherjee, R., Ogden, P. A., Ong, R. A., Perkins, J. S., Pizlo, F., Pohl, M., Quinn, J., Ragan, K., Reynolds, P. T., Roache, E. T., Rose, H. J., Schroedter, M., Sembroski, G. H., Sleege, G., Steele, D., Swordy, S. P., Syson, A., Toner, J. A., Valcarcel, L., Vassiliev, V. V., Wakely, S. P., Weekes, T. C., White, R. J., Williams, D. A., and Wagner, R.
Subjects: Astrophysics
Abstract: The first atmospheric Cherenkov telescope of VERITAS (the Very Energetic Radiation Imaging Telescope Array System) has been in operation since February 2005. We present here a technical description of the instrument and a summary of its performance. The calibration methods are described, along with the results of Monte Carlo simulations of the telescope and comparisons between real and simulated data. The analysis of TeV $\gamma$-ray observations of the Crab Nebula, including the reconstructed energy spectrum, is shown to give results consistent with earlier measurements. The telescope is operating as expected and has met or exceeded all design specifications., Comment: Accepted by Astroparticle Physics
Published: 2006
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