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Archambault, S. ; Beilicke, M. ; Benbow, W. ; Berger, K. ; Bird, R. ; Bouvier, A. ; Buckley, J. H. ; Bugaev, V. ; Byrum, K. ; Cerruti, M. ; Chen, Xuhui ; Ciupik, L. ; Connolly, M. P. ; Cui, W. ; Duke, C. ; Dumm, J. ; Errando, M. ; Falcone, A. ; Federici, Simone ; Feng, Q. ; Finley, J. P. ; Fortson, L. ; Furniss, A. ; Galante, N. ; Gillanders, G. H. ; Griffin, S. ; Griffiths, S. T. ; Grube, J. ; Gyuk, G. ; Hanna, D. ; Holder, J. ; Hughes, G. ; Humensky, T. B. ; Kaaret, P. ; Kertzman, M. ; Khassen, Y. ; Kieda, D. ; Krawczynski, H. ; Lang, M. J. ; Madhavan, A. S. ; Maier, G. ; Majumdar, P. ; McArthur, S. ; McCann, A. ; Moriarty, P. ; Mukherjee, R. ; Nieto, D. ; de Bhroithe, A. O'Faolain ; Ong, R. A. ; Otte, A. N. ; Pandel, D. ; Park, N. ; Perkins, J. S. ; Pohl, Martin ; Popkow, A. ; Prokoph, H. ; Quinn, J. ; Ragan, K. ; Rajotte, J. ; Reyes, L. C. ; Reynolds, P. T. ; Richards, G. T. ; Roache, E. ; Sembroski, G. H. ; Sheidaei, F. ; Smith, A. W. ; Staszak, D. ; Telezhinsky, Igor O. ; Theiling, M. ; Tucci, J. V. ; Tyler, J. ; Varlotta, A. ; Vincent, S. ; Wakely, S. P. ; Weekes, T. C. ; Weinstein, A. ; Williams, D. A. ; Zitzer, B. ; McCollough, M. L.
We report results from TeV gamma-ray observations of the microquasar Cygnus X-3. The observations were made with the Very Energetic Radiation Imaging Telescope Array System (VERITAS) over a time period from 2007 June 11 to 2011 November 28. VERITAS is most sensitive to gamma rays at energies between 85 GeV and 30 TeV. The effective exposure time amounts to a total of about 44 hr, with the observations covering six distinct radio/X-ray states of the object. No significant TeV gamma-ray emission was detected in any of the states, nor with all observations combined. The lack of a positive signal, especially in the states where GeV gamma rays were detected, places constraints on TeV gamma-ray production in Cygnus X-3. We discuss the implications of the results.
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, Vikram 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. ; Nunez, 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, Igor O. ; Tesic, 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. ; Zitzer, B.
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 x 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.
Aliu, E. ; Archambault, S. ; Arlen, T. ; Aune, T. ; Beilicke, M. ; Benbow, W. ; Boettcher, Markus ; Bouvier, A. ; Buckley, J. H. ; Bugaev, V. ; Cesarini, A. ; Ciupik, L. ; Collins-Hughes, E. ; Connolly, M. P. ; Cui, W. ; Dickherber, R. ; Duke, C. ; Dumm, J. ; Errando, M. ; Falcone, A. ; Federici, Simone ; 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. ; Kaaret, P. ; Karlsson, N. ; 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 Bhroithe, A. O'Faolain ; Ong, R. A. ; Orr, M. ; Otte, A. N. ; Park, N. ; Perkins, J. S. ; Pichel, A. ; Pohl, Martin ; Prokoph, H. ; Quinn, J. ; Ragan, K. ; Reyes, L. C. ; Reynolds, P. T. ; Roache, E. ; Saxon, D. B. ; Sembroski, G. H. ; Staszak, D. ; Telezhinsky, Igor O. ; Tesic, G. ; Theiling, M. ; Thibadeau, S. ; Tsurusaki, K. ; Varlotta, A. ; Vassiliev, V. V. ; Vincent, S. ; Vivier, M. ; Wakely, S. P. ; Weekes, T. C. ; Weinstein, A. ; Welsing, R. ; Williams, D. A. ; Zitzer, B. ; Fortin, P. ; Horan, D. ; Fumagalli, M. ; Kaplan, K. ; Prochaska, J. X.
We report on VERITAS very high energy (VHE; E >= 100 GeV) observations of six blazars selected from the Fermi Large Area Telescope First Source Catalog (1FGL). The gamma-ray emission from 1FGL sources was extrapolated up to the VHE band, taking gamma-ray absorption by the extragalactic background light into account. This allowed the selection of six bright, hard-spectrum blazars that were good candidate TeV emitters. Spectroscopic redshift measurements were attempted with the Keck Telescope for the targets without Sloan Digital Sky Survey spectroscopic data. No VHE emission is detected during the observations of the six sources described here. Corresponding TeV upper limits are presented, along with contemporaneous Fermi observations and non-concurrent Swift UVOT and X-Ray Telescope data. The blazar broadband spectral energy distributions (SEDs) are assembled and modeled with a single-zone synchrotron self-Compton model. The SED built for each of the six blazars shows a synchrotron peak bordering between the intermediate-and high-spectrum-peak classifications, with four of the six resulting in particle-dominated emission regions.
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, Martin ; Prokoph, H. ; Quinn, J. ; Ragan, K. ; Reyes, L. C. ; Reynolds, P. T. ; Roache, E. ; Rose, H. J. ; Ruppel, J. ; Saxon, D. B. ; Schroedter, M. ; Sembroski, G. H. ; Sentuerk, G. D. ; Skole, C. ; Smith, A. W. ; Staszak, D. ; Telezhinsky, Igor O. ; 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. ; Zitzer, B.
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 <sigma upsilon >(95%) (CL) less than or similar to 10(-23) cm(3) s(-1), improving our limits from previous observations of dwarf spheroidal galaxies by at least a factor of 2 for dark matter particle masses m(chi) greater than or similar to 300 GeV. The lower limits on the decay lifetime are at the level of tau(95%) (CL) greater than or similar to 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.
Acharya, B. S. ; Aramo, C. ; Babic, A. ; Barrio, J. A. ; Baushev, Anton N. ; Tjus, J. Becker ; Berge, David ; Bohacova, M. ; Bonardi, A. ; Brown, A. ; Bugaev, V. ; Bulik, Tomasz ; Burton, M. ; Busetto, G. ; Caraveo, P. A. ; Carosi, R. ; Carr, John ; Chadwick, Paula M. ; Chudoba, J. ; Conforti, V. ; Connaughton, V. ; Contreras, J. L. ; Cotter, G. ; Dazzi, F. ; De Franco, A. ; de la Calle, I. ; Lopez, R. de los Reyes ; De Lotto, B. ; De Palma, F. ; Di Girolamo, T. ; Di Giulio, C. ; Di Pierro, F. ; Dournaux, J. -L. ; Dwarkadas, Vikram V. ; Ebr, J. ; Egberts, Kathrin ; Fesquet, M. ; Fleischhack, H. ; Font, L. ; Fontaine, G. ; Foerster, A. ; Füßling, Matthias ; Garcia, B. ; Lopez, R. Garcia ; Garczarczyk, M. ; Gargano, F. ; Garrido, D. ; Gaug, M. ; Giglietto, N. ; Giordano, F. ; Giuliani, A. ; Godinovic, N. ; Gonzalez, M. M. ; Grabarczyk, T. ; Hassan, T. ; Hoerandel, J. ; Hrabovsky, M. ; Hrupec, D. ; Humensky, T. B. ; Huovelin, J. ; Jamrozy, M. ; Janecek, P. ; Kaaret, P. E. ; Katz, U. ; Kaufmann, S. ; Khelifi, B. ; Kluzniak, W. ; Kocot, J. ; Komin, N. ; Kubo, H. ; Kushida, J. ; Lamanna, G. ; Lee, W. H. ; Lenain, J. -P. ; Lohse, T. ; Lombardi, S. ; Lopez-Coto, R. ; Lopez-Oramas, A. ; Lucarelli, F. ; Maccarone, M. C. ; Maier, G. ; Majumdar, P. ; Malaguti, G. ; Mandat, D. ; Mazziotta, Mario Nicola ; Meagher, K. ; Mirabal, N. ; Morselli, A. ; Moulin, Emmanuel ; Niemiec, J. ; Nievas, M. ; Nishijima, K. ; Nosek, D. ; Nunio, F. ; Ohishi, M. ; Ohm, S. ; Ong, R. A. ; Orito, R. ; Otte, N. ; Palatka, M. ; Pareschi, G. ; Pech, M. ; Persic, M. ; Pohl, Manuela ; Prouza, M. ; Quirrenbach, A. ; Raino, S. ; Fernandez, G. Rodriguez ; Romano, Patrizia ; Rovero, A. C. ; Rudak, B. ; Schovanek, P. ; Shayduk, M. ; Siejkowski, H. ; Sillanpaa, A. ; Stefanik, S. ; Stolarczyk, T. ; Szanecki, M. ; Szepieniec, T. ; Tejedor, L. A. ; Telezhinsky, Igor O. ; Teshima, M. ; Tibaldo, L. ; Tibolla, O. ; Tovmassian, G. ; Travnicek, P. ; Trzeciak, M. ; Vallania, P. ; van Eldik, C. ; Vercellone, S. ; Vigorito, C. ; Wagner, S. J. ; Wakely, S. P. ; Weinstein, A. ; Wierzcholska, A. ; Wilhelm, Alina ; Wojcik, P. ; Yoshikoshi, T.
Supernova remnants (SNRs) are among the most important targets for gamma-ray observatories. Being prominent non-thermal sources, they are very likely responsible for the acceleration of the bulk of Galactic cosmic rays (CRS). To firmly establish the SNR paradigm for the origin of cosmic rays, it should be confirmed that protons are indeed accelerated in, and released from, SNRs with the appropriate flux and spectrum. This can be done by detailed theoretical models which account for microphysics of acceleration and various radiation processes of hadrons and leptons. The current generation of Cherenkov telescopes has insufficient sensitivity to constrain theoretical models. A new facility, the Cherenkov Telescope Array (CTA), will have superior capabilities and may finally resolve this long standing issue of high-energy astrophysics. We want to assess the capabilities of CTA to reveal the physics of various types of SNRs in the initial 2000 years of their evolution. During this time, the efficiency to accelerate cosmic rays is highest. We perform time-dependent simulations of the hydrodynamics, the magnetic fields, the cosmic-ray acceleration, and the non-thermal emission for type Ia, Ic and IIP SNRs. We calculate the CTA response to the y-ray emission from these SNRs for various ages and distances, and we perform a realistic analysis of the simulated data. We derive distance limits for the detectability and resolvability of these SNR types at several ages. We test the ability of CTA to reconstruct their morphological and spectral parameters as a function of their distance. Finally, we estimate how well CTA data will constrain the theoretical models. (C) 2014 Elsevier B.V. All rights reserved.
Archambault, S. ; Arlen, T. ; Aune, T. ; Beilicke, M. ; Benbow, W. ; Bird, R. ; Boettcher, Markus ; Bouvier, A. ; Buckley, J. H. ; Bugaev, V. ; Ciupik, L. ; Collins-Hughes, E. ; Connolly, M. P. ; Cui, W. ; Dickherber, R. ; Dumm, J. ; Errando, M. ; Falcone, A. ; Federici, Simone ; Feng, Q. ; Finley, J. P. ; Fortson, L. ; Furniss, A. ; Galante, N. ; Gall, D. ; Garson, A. III. ; Gillanders, G. H. ; Griffin, S. ; Grube, J. ; Gusbar, C. ; Gyuk, G. ; Hanna, D. ; Holder, J. ; Hughes, G. ; Kaaret, P. ; Kertzman, M. ; Khassen, Y. ; Kieda, D. ; Krawczynski, H. ; Lamerato, A. ; Lang, M. J. ; Li, K. ; Madhavan, A. S. ; Maier, G. ; Majumdar, P. ; McArthur, S. ; McCann, A. ; Millis, J. ; Moriarty, P. ; Mukherjee, R. ; Nieto, D. ; Ong, R. A. ; Orr, M. ; Otte, A. N. ; Park, N. ; Perkins, J. S. ; Pohl, Martin ; Popkow, A. ; Prokoph, H. ; Quinn, J. ; Ragan, K. ; Reynolds, P. T. ; Richards, G. T. ; Roache, E. ; Roustazadeh, P. ; Saxon, D. B. ; Sembroski, G. H. ; Senturk, G. D. ; Skole, C. ; Staszak, D. ; Telezhinsky, Igor O. ; Tesic, G. ; Theiling, M. ; Varlotta, A. ; Vassiliev, V. V. ; Vincent, S. ; Wakely, S. P. ; Weinstein, A. ; Welsing, R. ; Williams, D. A. ; Zitzer, B.
We present the results of a multi-wavelength campaign targeting the blazar 1ES 1218+30.4 with observations with the 1.3 m McGraw-Hill optical telescope, the Rossi X-ray Timing Explorer (RXTE), the Fermi Gamma-Ray Space Telescope, and the Very Energetic Radiation Imaging Telescope Array System (VERITAS). The RXTE and VERITAS observations were spread over a 13 day period and revealed clear evidence for flux variability, and a strong X-ray and gamma-ray flare on 2009 February 26 (MJD 54888). The campaign delivered a well-sampled broadband energy spectrum with simultaneous RXTE and VERITAS very high energy (VHE, > 100 GeV) observations, as well as contemporaneous optical and Fermi observations. The 1ES 1218+30.4 broadband energy spectrum-the first with simultaneous X-ray and VHE gamma-ray energy spectra-is of particular interest as the source is located at a high cosmological redshift for a VHE source (z = 0.182), leading to strong absorption of VHE gamma rays by photons from the optical/infrared extragalactic background light (EBL) via gamma VHE +gamma EBL -> e(+) e(-)pair-creation processes. We model the data with a one-zone synchrotron self-Compton (SSC) emission model and with the extragalactic absorption predicted by several recent EBL models. We find that the observations are consistent with the SSC scenario and all the EBL models considered in this work. We discuss observational and theoretical avenues to improve on the EBL constraints.
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. ; Schrödter, M. ; Sembroski, G. H. ; Sentuerk, G. D. ; Smith, A. W. ; Staszak, D. ; Telezhinsky, Igor O. ; 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. ; Kondratiev, V.
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 15,366 GRPs were recorded during 11.6 hr of simultaneous observations, which were made across four nights in 2008 December and in 2009 November and December. 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, eight 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. Furthermore, 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 timescales. On similar to 8 s timescales 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.
Aliu, E. ; Aune, T. ; Behera, B. ; Beilicke, M. ; Benbow, W. ; Berger, K. ; Bird, R. ; Buckley, J. H. ; Bugaev, V. ; Cardenzana, J. V. ; Cerruti, M. ; Chen, X. ; Ciupik, L. ; Connolly, M. P. ; Cui, W. ; Duke, C. ; Dumm, J. ; Errando, M. ; Falcone, A. ; Federici, Simone ; Feng, Q. ; Finley, J. P. ; Fortin, P. ; Fortson, L. ; Furniss, A. ; Galante, N. ; Gillanders, G. H. ; Griffin, S. ; Griffiths, S. T. ; Grube, J. ; Gyuk, G. ; Hanna, D. ; Holder, J. ; Hughes, G. ; Humensky, T. B. ; Kaaret, P. ; Kargaltsev, Oleg ; Kertzman, M. ; Khassen, Y. ; Kieda, D. ; Krawczynski, H. ; Lang, M. J. ; Madhavan, A. S. ; Maier, G. ; Majumdar, P. ; McCann, A. ; Moriarty, P. ; Mukherjee, R. ; Nieto, D. ; Ong, R. A. ; Otte, A. N. ; Pandel, D. ; Perkins, J. S. ; Pohl, Manuela ; Popkow, A. ; Prokoph, H. ; Quinn, J. ; Ragan, K. ; Rajotte, J. ; Reyes, L. C. ; Reynolds, P. T. ; Richards, G. T. ; Roache, E. ; Sembroski, G. H. ; Skole, C. ; Staszak, D. ; Telezhinsky, Igor O. ; Theiling, M. ; Tucci, J. V. ; Tyler, J. ; Varlotta, A. ; Vincent, S. ; Wakely, S. P. ; Weekes, T. C. ; Weinstein, A. ; Welsing, R. ; Williams, D. A. ; Zitzer, B.
Multiwavelength observations of the AGN 1ES 0414+009 with veritas, FERMI-LAT, SWIFT-XRT, AND MDM
(2012)
Aliu, E. ; Archambault, S. ; Arlen, T. ; Aune, T. ; Beilicke, M. ; Benbow, W. ; Boettcher, Markus ; Bouvier, A. ; Bugaev, V. ; Cannon, A. ; Cesarini, A. ; Ciupik, L. ; Collins-Hughes, E. ; Connolly, M. P. ; Cui, W. ; Dickherber, R. ; Dumm, J. ; Errando, M. ; Falcone, A. ; Federici, Stefania ; 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. ; Hui, C. M. ; Imran, A. ; Jameil, O. ; Kaaret, P. ; Karlsson, N. ; Kertzman, M. ; Kerr, J. ; Khassen, Y. ; Kieda, D. ; Krawczynski, H. ; Krennrich, F. ; Lang, M. J. ; Lee, K. ; Madhavan, A. S. ; 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, Martin ; Quinn, J. ; Ragan, K. ; Reynolds, P. T. ; Roache, E. ; Ruppel, J. ; Saxon, D. B. ; Schroedter, M. ; Sembroski, G. H. ; Sentuerk, G. D. ; Smith, A. W. ; Staszak, D. ; Stroh, M. ; Telezhinsky, Igor O. ; Tesic, G. ; Theiling, M. ; Thibadeau, S. ; Tsurusaki, K. ; Varlotta, A. ; Vassiliev, V. V. ; Vivier, M. ; Wakely, S. P. ; Ward, J. E. ; Weinstein, A. ; Welsing, R. ; Williams, D. A. ; Zitzer, B.
We present observations of the BL Lac object 1ES 0414+009 in the >200 GeV gamma-ray band by the VERITAS array of Cherenkov telescopes. 1ES 0414+009 was observed by VERITAS between 2008 January and 2011 February, resulting in 56.2 hr of good quality pointed observations. These observations resulted in a detection of 822 events from the source corresponding to a statistical significance of 6.4 standard deviations (6.4 sigma) above the background. The source flux, showing no evidence for variability, is measured as (5.2 +/- 1.1(stat) +/- 2.6(sys)) x 10(-12) photons cm(-2) s(-1) above 200 GeV, equivalent to approximately 2% of the Crab Nebula flux above this energy. The differential photon spectrum from 230 GeV to 850 GeV is well fit by a power law with a photon index of Gamma = 3.4 +/- 0.5(stat) +/- 0.3(sys) and a flux normalization of (1.6 +/- 0.3(stat) +/- 0.8(sys)) x 10(-11) photons cm(-2) s(-1) at 300 GeV. We also present multiwavelength results taken in the optical (MDM), x-ray (Swift-XRT), and GeV (Fermi-LAT) bands and use these results to construct a broadband spectral energy distribution (SED). Modeling of this SED indicates that homogenous one-zone leptonic scenarios are not adequate to describe emission from the system, with a lepto-hadronic model providing a better fit to the data.
Aleksic, J. ; Ansoldi, S. ; Antonelli, L. A. ; Antoranz, P. ; Babic, A. ; Bangale, P. ; de Almeida, U. Barres ; Barrio, J. A. ; Becerra Gonzalez, J. ; Bednarek, W. ; Berger, K. ; Bernardini, E. ; Biland, A. ; Blanch Bigas, O. ; Bock, R. K. ; Bonnefoy, S. ; Bonnoli, G. ; Borracci, F. ; Bretz, T. ; Carmona, E. ; Carosi, A. ; Fidalgo, D. Carreto ; Colin, P. ; Colombo, E. ; Contreras, J. L. ; Cortina, J. ; Covino, S. ; Da Vela, P. ; Dazzi, F. ; De Angelis, A. ; De Caneva, G. ; De Lotto, B. ; Delgado Mendez, C. ; Doert, M. ; Dominguez, A. ; Prester, Dijana Dominis ; Dorner, D. ; Doro, M. ; Einecke, S. ; Eisenacher, D. ; Elsaesser, D. ; Farina, E. ; Ferenc, D. ; Fonseca, M. V. ; Font, L. ; Frantzen, K. ; Fruck, C. ; Garcia Lopez, R. J. ; Garczarczyk, M. ; Garrido Terrats, D. ; Gaug, M. ; Giavitto, G. ; Godinovic, N. ; Gonzalez Munoz, A. ; Gozzini, S. R. ; Hadamek, A. ; Hadasch, D. ; Herrero, A. ; Hildebrand, D. ; Hose, J. ; Hrupec, D. ; Idec, W. ; Kadenius, V. ; Kellermann, H. ; Knoetig, M. L. ; Krause, J. ; Kushida, J. ; La Barbera, A. ; Lelas, D. ; Lewandowska, N. ; Lindfors, E. ; Lombardi, S. ; Lopez, M. ; Lopez-Coto, R. ; Lopez-Oramas, A. ; Lorenz, E. ; Lozano, I. ; Makariev, M. ; Mallot, K. ; Maneva, G. ; Mankuzhiyil, N. ; Mannheim, K. ; Maraschi, L. ; Marcote, B. ; Mariotti, M. ; Martinez, M. ; Mazin, D. ; Menzel, U. ; Meucci, M. ; Miranda, J. M. ; Mirzoyan, R. ; Moralejo, A. ; Munar-Adrover, P. ; Nakajima, D. ; Niedzwiecki, A. ; Nilsson, K. ; Nowak, N. ; Orito, R. ; Overkemping, A. ; Paiano, S. ; Palatiello, M. ; Paneque, D. ; Paoletti, R. ; Paredes, J. M. ; Paredes-Fortuny, X. ; Partini, S. ; Persic, M. ; Prada, F. ; Moroni, P. G. Prada ; Prandini, E. ; Preziuso, S. ; Puljak, I. ; Reinthal, R. ; Rhode, W. ; Ribo, M. ; Rico, J. ; Garcia, J. Rodriguez ; Ruegamer, S. ; Saggion, A. ; Saito, T. ; Saito, K. ; Salvati, M. ; Satalecka, K. ; Scalzotto, V. ; Scapin, V. ; Schultz, C. ; Schweizer, T. ; Shore, S. N. ; Sillanpaa, A. ; Sitarek, J. ; Snidaric, I. ; Sobczynska, D. ; Spanier, F. ; Stamatescu, V. ; Stamerra, A. ; Steinbring, T. ; Storz, J. ; Sun, S. ; Suric, T. ; Takalo, L. ; Tavecchio, F. ; Temnikov, P. ; Terzic, T. ; Tescaro, D. ; Teshima, M. ; Thaele, J. ; Tibolla, O. ; Torres, D. F. ; Toyama, T. ; Treves, A. ; Uellenbeck, M. ; Vogler, P. ; Wagner, R. M. ; Zandanel, F. ; Zanin, R. ; Behera, B. ; Beilicke, M. ; Benbow, W. ; Berger, K. ; Bird, R. ; Bouvier, A. ; Bugaev, V. ; Cerruti, M. ; Chen, Xuhui ; Ciupik, L. ; Collins-Hughes, E. ; Cui, W. ; Duke, C. ; Dumm, J. ; Falcone, A. ; Federici, Simone ; Feng, Q. ; Finley, J. P. ; Fortson, L. ; Furniss, A. ; Galante, N. ; Gillanders, G. H. ; Griffin, S. ; Griffiths, S. T. ; Grube, J. ; Gyuk, G. ; Hanna, D. ; Holder, J. ; Johnson, C. A. ; Kaaret, P. ; Kertzman, M. ; Kieda, D. ; Krawczynski, H. ; Lang, M. J. ; Madhavan, A. S. ; Maier, G. ; Majumdar, P. ; Meagher, K. ; Moriarty, P. ; Mukherjee, R. ; Nieto, D. ; Ong, R. A. ; Otte, A. N. ; Pichel, A. ; Pohl, Manula ; Popkow, A. ; Prokoph, H. ; Quinn, J. ; Rajotte, J. ; Ratliff, G. ; Reyes, L. C. ; Reynolds, P. T. ; Richards, G. T. ; Roache, E. ; Sembroski, G. H. ; Shahinyan, K. ; Sheidaei, F. ; Smith, A. W. ; Staszak, D. ; Telezhinsky, Igor O. ; Theiling, M. ; Tyler, J. ; Varlotta, A. ; Vincent, S. ; Wakely, S. P. ; Weekes, T. C. ; Welsing, R. ; Williams, D. A. ; Zajczyk, A. ; Zitzer, B. ; Villata, M. ; Raiteri, C. M. ; Ajello, M. ; Perri, M. ; Aller, H. D. ; Aller, M. F. ; Larionov, V. M. ; Efimova, N. V. ; Konstantinova, T. S. ; Kopatskaya, E. N. ; Chen, W. P. ; Koptelova, E. ; Hsiao, H. Y. ; Kurtanidze, O. M. ; Nikolashvili, M. G. ; Kimeridze, G. N. ; Jordan, B. ; Leto, Paolo ; Buemi, C. S. ; Trigilio, C. ; Umana, G. ; Lahteenmaki, A. ; Nieppola, E. ; Tornikoski, M. ; Sainio, J. ; Kadenius, V. ; Giroletti, M. ; Cesarini, A. ; Fuhrmann, L. ; Kovalev, Yu. A. ; Kovalev, Y. Y.
Context. Blazars are variable sources on various timescales over a broad energy range spanning from radio to very high energy (>100 GeV, hereafter VHE). Mrk 501 is one of the brightest blazars at TeV energies and has been extensively studied since its first VHE detection in 1996. However, most of the gamma-ray studies performed on Mrk 501 during the past years relate to flaring activity, when the source detection and characterization with the available gamma-ray instrumentation was easier to perform.
Aims. Our goal is to characterize the source gamma-ray emission in detail, together with the radio-to-X-ray emission, during the non-flaring (low) activity, which is less often studied than the occasional flaring (high) activity.
Methods. We organized a multiwavelength (MW) campaign on Mrk 501 between March and May 2008. This multi-instrument effort included the most sensitive VHE gamma-ray instruments in the northern hemisphere, namely the imaging atmospheric Cherenkov telescopes MAGIC and VERITAS, as well as Swift, RXTE, the F-GAMMA, GASP-WEBT, and other collaborations and instruments. This provided extensive energy and temporal coverage of Mrk 501 throughout the entire campaign.
Results. Mrk 501 was found to be in a low state of activity during the campaign, with a VHE flux in the range of 10%-20% of the Crab nebula flux. Nevertheless, significant flux variations were detected with various instruments, with a trend of increasing variability with energy and a tentative correlation between the X-ray and VHE fluxes. The broadband spectral energy distribution during the two different emission states of the campaign can be adequately described within the homogeneous one-zone synchrotron self-Compton model, with the (slightly) higher state described by an increase in the electron number density.
Conclusions. The one-zone SSC model can adequately describe the broadband spectral energy distribution of the source during the two months covered by the MW campaign. This agrees with previous studies of the broadband emission of this source during flaring and non-flaring states. We report for the first time a tentative X-ray-to-VHE correlation during such a low VHE activity. Although marginally significant, this positive correlation between X-ray and VHE, which has been reported many times during flaring activity, suggests that the mechanisms that dominate the X-ray/VHE emission during non-flaring-activity are not substantially different from those that are responsible for the emission during flaring activity.