@article{AleksicAnsoldiAntonellietal.2015,
  author    = {Aleksic, J. and Ansoldi, S. and Antonelli, L. A. and Antoranz, P. and Babic, A. and Bangale, P. and de Almeida, U. Barres and Barrio, J. A. and Gonzalez, J. Becerra and Bednarek, W. and Berger, K. and Bernardini, E. and Bilandli, A. and Bianch, O. and Bock, R. K. and Bonnefoy, S. and Bonnoli, G. and Borracci, F. and Bretz, T. and Carmona, E. and Carosi, A. and Fidalgo, D. Carreto and Colin, P. and Colombo, E. and Contreras, J. L. and Cortina, J. and Covino, S. and Da Vela, P. and Dazzi, F. and De Angelis, A. and De Caneva, G. and De Lotto, B. and Delgado Mendez, C. and Doert, M. and Dominguez, A. and Prester, Dijana Dominis and Dorner, D. and Doro, M. and Einecke, S. and Eisenacher, D. and Elsaesser, D. and Farina, E. and Ferenc, D. and Fonseca, M. V. and Font, L. and Frantzen, K. and Fruck, C. and Garcia Lopez, R. J. and Garczarczyki, M. and Garrido Terrats, D. and Gaug, M. and Giavitto, G. and Godinovic, N. and Gonzalez Munoz, A. and Gozzini, S. R. and Hadamek, A. and Hadasch, D. and Herrero, A. and Hildebrand, D. and Hose, J. and Hrupec, D. and Idec, W. and Kadenius, V. and Kellermann, H. and Knoetig, M. L. and Krause, J. and Kushida, J. and La Barbera, A. and Lelas, D. and Lewandowska, N. and Lindfors, E. and Longo, F. and Lombardi, S. and Lopez, M. and Lopez-Coto, R. and Lopez-Oramas, A. and Lorenz, E. and Lozano, I. and Makariev, M. and Mallot, K. and Maneva, G. and Mankuzhiyil, N. and Mannheim, K. and Maraschi, L. and Marcote, B. and Mariotti, M. and Martinez, M. and Mazin, D. and Menzel, U. and Meucci, M. and Miranda, J. M. and Mirzoyan, R. and Moralejo, A. and Munar-Adrover, P. and Nakajima, D. and Niedzwiecki, A. and Nilsson, K. and Nowak, N. and Orito, R. and Overkemping, A. and Paiano, S. and Palatiello, M. and Paneque, D. and Paoletti, R. and Paredes, J. M. and Paredes-Fortuny, X. and Partini, S. and Persic, M. and Prada, F. and Moroni, P. G. Prada and Prandini, E. and Preziuso, S. and Puljak, I. and Reinthal, R. and Rhode, W. and Ribo, M. and Rico, J. and Garcia, J. Rodriguez and Ruegamer, S. and Saggion, A. and Saito, K. and Salvati, M. and Satalecka, K. and Scalzotto, V. and Scapin, V. and Schuliz, C. and Schweizer, T. and Shore, S. N. and Sillanpaa, A. and Sitarek, J. and Snidaric, I. and Sobczynska, D. and Spanier, F. and Stamatescu, V. and Stamerra, A. and Steinbring, T. and Storz, J. and Sun, S. and Suric, T. and Takalo, L. and Tavecchio, F. and Temnikov, P. and Terzic, T. and Tescaro, D. and Teshima, M. and Thaele, J. and Tibolla, O. and Torres, D. F. and Toyama, T. and Treves, A. and Uellenbeck, M. and Vogler, P. and Wagner, R. M. and Zandanel, F. and Zanin, R. and Archambault, S. and Behera, B. and Beilicke, M. and Benbow, W. and Bird, R. and Buckley, J. H. and Bugaev, V. and Cerruti, M. and Chen, X. and Ciupik, L. and Collins-Hughes, E. and Cui, W. and Dumm, J. and Eisch, J. D. and Falcone, A. and Federici, S. and Feng, Q. and Finley, J. P. and Fleischhack, H. and Fortin, P. and Fortson, L. and Furniss, A. and Griffin, S. and Griffiths, S. T. and Grube, J. and Gyuk, G. and Hanna, D. and Holder, J. and Hughes, G. and Humensky, T. B. and Johnson, C. A. and Kaaret, P. and Kertzman, M. and Khassen, Y. and Kieda, D. and Krawczynski, H. and Krennrich, F. and Kumar, S. and Lang, M. J. and Maier, G. and McArthur, S. and Meagher, K. and Moriarty, P. and Mukherjee, R. and Ong, R. A. and Otte, A. N. and Park, N. and Pichel, A. and Pohl, M. and Popkow, A. and Prokoph, H. and Quinn, M. J. and Ragan, K. and Rajotte, J. and Reynolds, P. T. and Richards, G. T. and Roache, E. and Rovero, A. C. and Sembroski, G. H. and Shahinyan, K. and Staszak, D. and Telezhinsky, Igor O. and Theiling, M. and Tucci, J. V. and Tyler, J. and Varlotta, A. and Wakely, S. P. and Weekes, T. C. and Weinstein, A. and Welsing, R. and Wilhelm, Alina and Williams, D. A. and Zitzer, B. and Villata, M. and Raiteri, C. and Aller, H. D. and Aller, M. F. and Chen, W. P. and Jordan, B. and Koptelova, E. and Kurtanidze, O. M. and Lahteenmaki, A. and McBreen, B. and Larionov, V. M. and Lin, C. S. and Nikolashvili, M. G. and Angelakis, E. and Capalbi, M. and Carraminana, A. and Carrasco, L. and Cassaro, P. and Cesarini, A. and Fuhrmann, L. and Giroletti, M. and Hovatta, T. and Krichbaum, T. P. and Krimm, H. A. and Max-Moerbeck, W. and Moody, J. W. and Maccaferri, G. and Mori, Y. and Nestoras, I. and Orlati, A. and Pace, C. and Pearson, R. and Perri, M. and Readhead, A. C. S. and Richards, J. L. and Sadun, A. C. and Sakamoto, T. and Tammi, J. and Tornikoski, M. and Yatsu, Y. and Zook, A.},
  title     = {The 2009 multiwavelength campaign on Mrk 421: Variability and correlation studies},
  series = {Astronomy and astrophysics : an international weekly journal},
  volume    = {576},
  journal   = {Astronomy and astrophysics : an international weekly journal},
  publisher = {EDP Sciences},
  address   = {Les Ulis},
  organization    = {MAGIC Collaboration, VERITAS Collaboration, MAGIC Collaboration},
  issn      = {0004-6361},
  doi       = {10.1051/0004-6361/201424216},
  pages     = {18},
  year      = {2015},
  abstract  = {Aims. We perform an extensive characterization of the broadband emission of Mrk 421, as well as its temporal evolution, during the non-flaring (low) state. The high brightness and nearby location (z = 0.031) of Mrk 421 make it an excellent laboratory to study blazar emission. The goal is to learn about the physical processes responsible for the typical emission of Mrk 421, which might also be extended to other blazars that are located farther away and hence are more difficult to study. Methods. We performed a 4.5-month multi-instrument campaign on Mrk 421 between January 2009 and June 2009, which included VLBA, F-GAMMA, GASP-WEBT, Swift, RXTE, Fermi-LAT, MAGIC, and Whipple, among other instruments and collaborations. This extensive radio to very-high-energy (VHE; E > 100 GeV) gamma-ray dataset provides excellent temporal and energy coverage, which allows detailed studies of the evolution of the broadband spectral energy distribution. Results. Mrk421 was found in its typical (non-flaring) activity state, with a VHE flux of about half that of the Crab Nebula, yet the light curves show significant variability at all wavelengths, the highest variability being in the X-rays. We determined the power spectral densities (PSD) at most wavelengths and found that all PSDs can be described by power-laws without a break, and with indices consistent with pink/red-noise behavior. We observed a harder-when-brighter behavior in the X-ray spectra and measured a positive correlation between VHE and X-ray fluxes with zero time lag. Such characteristics have been reported many times during flaring activity, but here they are reported for the first time in the non-flaring state. We also observed an overall anti-correlation between optical /UV and X-rays extending over the duration of the campaign. Conclusions. The harder-when-brighter behavior in the X-ray spectra and the measured positive X-ray/VHE correlation during the 2009 multiwavelength campaign suggests that the physical processes dominating the emission during non-flaring states have similarities with those occurring during flaring activity. In particular, this observation supports leptonic scenarios as being responsible for the emission of Mrk 421 during non-flaring activity. Such a temporally extended X-ray /VHE correlation is not driven by any single flaring event, and hence is difficult to explain within the standard hadronic scenarios. The highest variability is observed in the X-ray band, which, within the one-zone synchrotron self-Compton scenario, indicates that the electron energy distribution is most variable at the highest energies.},
  language  = {en}
}
@article{OrientiFinkeRaiterietal.2015,
  author    = {Orienti, M. and Finke, J. and Raiteri, C. M. and Hovatta, T. and Larsson, J. and Max-Moerbeck, W. and Perkins, J. and Readhead, A. C. S. and Richards, J. L. and Beilicke, M. and Benbow, W. and Berger, K. and Bird, R. and Bugaev, V. and Cardenzana, J. V. and Cerruti, M. and Chen, Xuhui and Ciupik, L. and Dickinson, H. J. and Eisch, J. D. and Errando, M. and Falcone, A. and Finley, J. P. and Fleischhack, H. and Fortin, P. and Fortson, L. and Furniss, A. and Gerard, L. and Gillanders, G. H. and Griffiths, S. T. and Grube, J. and Gyuk, G. and Hakansson, Nils and Holder, J. and Humensky, T. B. and Kar, P. and Kertzman, M. and Khassen, Y. and Kieda, D. and Krennrich, F. and Kumar, S. and Lang, M. J. and Maier, G. and McCann, A. and Meagher, K. and Moriarty, P. and Mukherjee, R. and Nieto, D. and Ong, R. A. and Otte, A. N. and Pohl, Manuela and Popkow, A. and Prokoph, H. and Pueschel, Elisa and Quinn, J. and Ragan, K. and Reynolds, P. T. and Richards, G. T. and Roache, E. and Rousselle, J. and Santander, M. and Sembroski, G. H. and Smith, A. W. and Staszak, D. and Telezhinsky, Igor O. and Tucci, J. V. and Tyler, J. and Varlotta, A. and Vassiliev, V. V. and Wakely, S. P. and Weinstein, A. and Welsing, R. and Williams, D. A. and Zitzer, B.},
  title     = {The most powerful flaring activity from the NLSyl PMN J0948+0022},
  series = {Monthly notices of the Royal Astronomical Society},
  volume    = {446},
  journal   = {Monthly notices of the Royal Astronomical Society},
  number    = {3},
  publisher = {Oxford Univ. Press},
  address   = {Oxford},
  organization    = {VERITAS Collaboration},
  issn      = {0035-8711},
  doi       = {10.1093/mnras/stu2251},
  pages     = {2456 -- 2467},
  year      = {2015},
  abstract  = {We report on multifrequency observations performed during 2012 December-2013 August of the first narrow-line Seyfert 1 galaxy detected in gamma-rays, PMN J0948+0022 (z = 0.5846). A y -ray flare was observed by the Large Area Telescope on board Fermi during 2012 December-2013 January, reaching a daily peak flux in the 0.1-100 GeV energy range of (155 31) x 10 8 ph cm(-2) S-1 on 2013 January 1, corresponding to an apparent isotropic luminosity of similar to 1.5 x 1048 erg s(-1). The y -ray flaring period triggered Swift and Very Energetic Radiation Imaging Telescope Array System (VERITAS) observations in addition to radio and optical monitoring by Owens Valley Radio Observatory, Monitoring Of Jets in Active galactic nuclei with VLBA Experiments, and Catalina Real-time Transient Survey. A strong flare was observed in optical, UV, and X-rays on 2012 December 30, quasi-simultaneously to the y -ray flare, reaching a record flux for this source from optical to y gamma-rays. VERITAS observations at very high energy (E > 100 GeV) during 2013 January 6-17 resulted in an upper limit of F>0.2 Trev < 4.0 x 10(-12) ph cm(-2) s(-1). We compared the spectral energy distribution (SED) of the flaring state in 2013 January with that of an intermediate state observed in 2011. The two SEDs, modelled as synchrotron emission and an external Compton scattering of seed photons from a dust torus, can be modelled by changing both the electron distribution parameters and the magnetic field.},
  language  = {en}
}
@article{AliuArcherAuneetal.2015,
  author    = {Aliu, E. and Archer, A. and Aune, T. and Barnacka, Anna and Behera, B. and Beilicke, M. and Benbow, W. and Berger, K. and Bird, R. and Buckley, J. H. and Bugaev, V. and Byrum, K. and Cardenzana, J. V. and Cerruti, M. and Chen, Xuhui and Ciupik, L. and Connolly, M. P. and Cui, Wei and Dickinson, H. J. and Dumm, J. and Eisch, J. D. and Errando, M. and Falcone, A. and Federici, Simone and Feng, Q. and Finley, J. P. and Fortin, P. and Fortson, L. and Furniss, A. and Galante, N. and Gillanders, G. H. and Griffin, S. and Griffiths, S. T. and Grube, J. and Gyuk, G. and Hakansson, Nils and Hanna, D. and Holder, J. and Hughes, G. and Humensky, T. B. and Johnson, C. A. and Kaaret, P. and Kar, P. and Kertzman, M. and Khassen, Y. and Kieda, D. and Krawczynski, H. and Krennrich, F. and Kumar, S. and Lang, M. J. and Madhavan, A. and McArthur, S. and McCann, A. and Meagher, K. and Millis, J. and Moriarty, P. and Nieto, Daniel and Ong, R. A. and Orr, M. and Otte, A. N. and Park, N. and Perkins, J. S. and Pohl, Martin and Popkow, A. and Prokoph, H. and Pueschel, Elisa and Quinn, J. and Ragan, K. and Rajotte, J. and Reyes, L. C. and Reynolds, P. T. and Richards, G. T. and Roache, E. and Sembroski, G. H. and Shahinyan, K. and Staszak, D. and Telezhinsky, Igor O. and Tucci, J. V. and Tyler, J. and Varlotta, A. and Vassiliev, V. V. and Wakely, S. P. and Weinstein, A. and Welsing, R. and Wilhelm, Alina and Williams, D. A. and Zitzer, B.},
  title     = {Veritas observations of the BL LAC OBJECT PG 1553+113},
  series = {The astrophysical journal : an international review of spectroscopy and astronomical physics},
  volume    = {799},
  journal   = {The astrophysical journal : an international review of spectroscopy and astronomical physics},
  number    = {1},
  publisher = {IOP Publ. Ltd.},
  address   = {Bristol},
  issn      = {0004-637X},
  doi       = {10.1088/0004-637X/799/1/7},
  pages     = {9},
  year      = {2015},
  abstract  = {We present results from VERITAS observations of the BL Lac object PG 1553+113 spanning the years 2010, 2011, and 2012. The time-averaged spectrum, measured between 160 and 560 GeV, is well described by a power law with a spectral index of 4.33 +/- 0.09. The time-averaged integral flux above 200 GeV measured for this period was (1.69 +/- 0.06) x 10(-11) photons cm(-2) s(-1), corresponding to 6.9\% of the Crab Nebula flux. We also present the combined gamma-ray spectrum from the Fermi Large Area Telescope and VERITAS covering an energy range from 100 MeV to 560 GeV. The data are well fit by a power law with an exponential cutoff at 101.9 +/- 3.2 GeV. The origin of the cutoff could be intrinsic to PG 1553+113 or be due to the gamma-ray opacity of our universe through pair production off the extragalactic background light (EBL). Given lower limits to the redshift of z > 0.395 based on optical/UV observations of PG 1553+113, the cutoff would be dominated by EBL absorption. Conversely, the small statistical uncertainties of the VERITAS energy spectrum have allowed us to provide a robust upper limit on the redshift of PG 1553+113 of z <= 0.62. A strongly elevated mean flux of (2.50 +/- 0.14) x10(-11) photons cm(-2) s(-1) (10.3\% of the Crab Nebula flux) was observed during 2012, with the daily flux reaching as high as (4.44 +/- 0.71) x10(-11) photons cm(-2) s(-1) (18.3\% of the Crab Nebula flux) on MJD 56048. The light curve measured during the 2012 observing season is marginally inconsistent with a steady flux, giving a chi(2) probability for a steady flux of 0.03\%.},
  language  = {en}
}