@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 Bernardini, E. and Biasuzzi, B. and Biland, A. and Blanch Bigas, O. and Boller, A. and Bonnefoy, S. and Bonnoli, G. and Borracci, F. and Bretz, T. and Carmona, E. and Carosi, A. 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 Wilhelmi, E. de Ona and Mendez, C. Delgado and Prester, Dijana Dominis and Dorner, D. and Doro, M. and Einecke, S. and Eisenacher, D. and Elsaesser, D. and Fonseca, M. V. and Font, L. and Frantzen, K. and Fruck, C. and Galindo, D. and Lopez, R. J. Garcia and Garczarczyk, M. and Terrats, D. Garrido and Gaug, M. and Godinovic, N. and Munoz, A. Gonzalez and Gozzini, S. R. and Hadasch, D. and Hanabata, Y. and Hayashida, M. and Herrera, J. and Hildebrand, D. and Hose, J. and Hrupec, D. and Hughes, G. and Idec, W. and Kadenius, V. and Kellermann, H. and Knoetig, M. L. and Kodani, K. and Konno, Y. and Krause, J. and Kubo, H. and Kushida, J. and La Barbera, A. and Lelas, D. and Lewandowska, N. and Lindfors, E. 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 Miranda, J. M. and Mirzoyan, R. and Moralejo, A. and Munar-Adrover, P. and Nakajima, D. and Niedzwiecki, A. and Nilsson, K. and Nishijima, K. and Noda, K. 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 Persic, M. and Moroni, P. G. Prada and Prandini, E. and Puljak, I. and Reinthal, R. and Rhode, W. and Ribo, M. and Rico, J. and Garcia, J. Rodriguez and Rugamer, S. and Saito, T. and Saito, K. and Satalecka, K. and Scalzotto, V. and Scapin, V. and Schultz, C. and Schweizer, T. and Sun, S. 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 Steinke, B. and Storz, J. and Strzys, M. and Takalo, L. and Takami, H. 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 Zanin, R. and Archambault, S. and Archer, A. and Beilicke, M. and Benbow, W. and Berger, K. and Bird, R. and Biteau, Jonathan and Buckley, J. H. and Bugaev, V. and Cerruti, M. and Chen, Xiaoming and Ciupik, L. and Collins-Hughes, E. and Cui, W. and Eisch, J. D. and Falcone, A. 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 Gyuk, G. and Hakansson, Nils and Holder, J. and Johnson, C. A. and Kaaret, P. and Kar, P. and Kertzman, M. and Kieda, D. and Lang, M. J. and McArthur, S. and McCann, A. and Meagher, K. and Millis, J. and Moriarty, P. and Ong, R. A. and Otte, A. N. and Perkins, J. S. and Pichel, A. and Pohl, Manuela and Popkow, A. and Prokoph, H. and Pueschel, Elisa and Ragan, K. and Reyes, L. C. 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 Tucci, J. V. and Tyler, J. and Varlotta, A. and Wakely, S. P. and Welsing, R. and Wilhelm, Alina and Williams, D. A. and Buson, S. and Finke, J. and Villata, M. and Raiteri, C. and Aller, H. D. and Aller, M. F. and Cesarini, A. and Chen, W. P. and Gurwell, M. A. and Jorstad, S. G. and Kimeridze, G. N. and Koptelova, E. and Kurtanidze, O. M. and Kurtanidze, S. O. and Lahteenmaki, A. and Larionov, V. M. and Larionova, E. G. and Lin, H. C. and McBreen, B. and Moody, J. W. and Morozova, D. A. and Marscher, A. P. and Max-Moerbeck, W. and Nikolashvili, M. G. and Perri, M. and Readhead, A. C. S. and Richards, J. L. and Ros, J. A. and Sadun, A. C. and Sakamoto, T. and Sigua, L. A. and Smith, P. S. and Tornikoski, M. and Troitsky, I. S. and Wehrle, A. E. and Jordan, B.},
  title     = {Unprecedented study of the broadband emission of Mrk 421 during flaring activity in March 2010},
  series = {Astronomy and astrophysics : an international weekly journal},
  volume    = {578},
  journal   = {Astronomy and astrophysics : an international weekly journal},
  publisher = {EDP Sciences},
  address   = {Les Ulis},
  organization    = {MAGIC Collaboration, VERITAS Collaboration},
  issn      = {0004-6361},
  doi       = {10.1051/0004-6361/201424811},
  pages     = {26},
  year      = {2015},
  abstract  = {Context. Because of its proximity, Mrk 421 is one of the best sources on which to study the nature of BL Lac objects. Its proximity allows us to characterize its broadband spectral energy distribution (SED). Aims. The goal is to better understand the mechanisms responsible for the broadband emission and the temporal evolution of Mrk 421. These mechanisms may also apply to more distant blazars that cannot be studied with the same level of detail. Methods. A flare occurring in March 2010 was observed for 13 consecutive days (from MJD 55 265 to MJD 55 277) with unprecedented wavelength coverage from radio to very high energy (VHE; E > 100 GeV) gamma-rays with MAGIC, VERITAS, Whipple, Fermi-LAT, MAXI, RXTE, Swift, GASP-WEBT, and several optical and radio telescopes. We modeled the day-scale SEDs with one-zone and two-zone synchrotron self-Compton (SSC) models, investigated the physical parameters, and evaluated whether the observed broadband SED variability can be associated with variations in the relativistic particle population. Results. The activity of Mrk 421 initially was high and then slowly decreased during the 13-day period. The flux variability was remarkable at the X-ray and VHE bands, but it was minor or not significant at the other bands. The variability in optical polarization was also minor. These observations revealed an almost linear correlation between the X-ray flux at the 2-10 keV band and the VHE gamma-ray flux above 200 GeV, consistent with the gamma-rays being produced by inverse-Compton scattering in the Klein-Nishina regime in the framework of SSC models. The one-zone SSC model can describe the SED of each day for the 13 consecutive days reasonably well, which once more shows the success of this standard theoretical scenario to describe the SEDs of VHE BL Lacs such as Mrk 421. This flaring activity is also very well described by a two-zone SSC model, where one zone is responsible for the quiescent emission, while the other smaller zone, which is spatially separated from the first, contributes to the daily variable emission occurring at X-rays and VHE gamma-rays. The second blob is assumed to have a smaller volume and a narrow electron energy distribution with 3 x 10(4) < gamma < 6 x 10(5), where. is the Lorentz factor of the electrons. Such a two-zone scenario would naturally lead to the correlated variability at the X-ray and VHE bands without variability at the optical/UV band, as well as to shorter timescales for the variability at the X-ray and VHE bands with respect to the variability at the other bands. Conclusions. Both the one-zone and the two-zone SSC models can describe the daily SEDs via the variation of only four or five model parameters, under the hypothesis that the variability is associated mostly with the underlying particle population. This shows that the particle acceleration and cooling mechanism that produces the radiating particles might be the main mechanism responsible for the broadband SED variations during the flaring episodes in blazars. The two-zone SSC model provides a better agreement with the observed SED at the narrow peaks of the low-and high-energy bumps during the highest activity, although the reported one-zone SSC model could be further improved by varying the parameters related to the emitting region itself (delta, B and R), in addition to the parameters related to the particle population.},
  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{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{ArlenAuneBeilickeetal.2013,
  author    = {Arlen, T. and Aune, T. and Beilicke, M. and Benbow, W. and Bouvier, A. and Buckley, J. H. and Bugaev, V. and Cesarini, A. and Ciupik, L. and Connolly, M. P. and Cui, W. and Dickherber, R. and Dumm, J. and Errando, M. and Falcone, A. and Federici, S. and Feng, Q. and Finley, J. P. and Finnegan, G. and Fortson, L. and Furniss, A. and Galante, N. and Gall, D. and Griffin, S. and Grube, J. and Gyuk, G. and Hanna, D. and Holder, J. and Humensky, T. B. and Kaaret, P. and Karlsson, N. and Kertzman, M. and Khassen, Y. and Kieda, D. and Krawczynski, H. and Krennrich, F. and Maier, G. and Moriarty, P. and Mukherjee, R. and Nelson, T. and de Bhroithe, A. O'Faolain and Ong, R. A. and Orr, M. and Park, N. and Perkins, J. S. and Pichel, A. and Pohl, Martin and Prokoph, H. and Quinn, J. and Ragan, K. and Reyes, L. C. and Reynolds, P. T. and Roache, E. and Saxon, D. B. and Schroedter, M. and Sembroski, G. H. and Staszak, D. and Telezhinsky, Igor O. and Tesic, G. and Theiling, M. and Tsurusaki, K. and Varlotta, A. and Vincent, S. and Wakely, S. P. and Weekes, T. C. and Weinstein, A. and Welsing, R. and Williams, D. A. and Zitzer, B. and Jorstad, S. G. and MacDonald, N. R. and Marscher, A. P. and Smith, P. S. and Walker, R. C. and Hovatta, T. and Richards, J. and Max-Moerbeck, W. and Readhead, A. and Lister, M. L. and Kovalev, Y. Y. and Pushkarev, A. B. and Gurwell, M. A. and Lahteenmaki, A. and Nieppola, E. and Tornikoski, M. and Jarvela, E.},
  title     = {Rapid TeV Gamma-Ray flaring of bl lacertae},
  series = {The astrophysical journal : an international review of spectroscopy and astronomical physics},
  volume    = {762},
  journal   = {The astrophysical journal : an international review of spectroscopy and astronomical physics},
  number    = {2},
  publisher = {IOP Publ. Ltd.},
  address   = {Bristol},
  organization    = {VERITAS Collaboration},
  issn      = {0004-637X},
  doi       = {10.1088/0004-637X/762/2/92},
  pages     = {13},
  year      = {2013},
  abstract  = {We report on the detection of a very rapid TeV gamma-ray flare from BL Lacertae on 2011 June 28 with the Very Energetic Radiation Imaging Telescope Array System (VERITAS). The flaring activity was observed during a 34.6 minute exposure, when the integral flux above 200 GeV reached (3.4 +/- 0.6) x 10(-6) photons m(-2) s(-1), roughly 125\% of the Crab Nebula flux measured by VERITAS. The light curve indicates that the observations missed the rising phase of the flare but covered a significant portion of the decaying phase. The exponential decay time was determined to be 13 +/- 4 minutes, making it one of the most rapid gamma-ray flares seen from a TeV blazar. The gamma-ray spectrum of BL Lacertae during the flare was soft, with a photon index of 3.6 +/- 0.4, which is in agreement with the measurement made previously by MAGIC in a lower flaring state. Contemporaneous radio observations of the source with the Very Long Baseline Array revealed the emergence of a new, superluminal component from the core around the time of the TeV gamma-ray flare, accompanied by changes in the optical polarization angle. Changes in flux also appear to have occurred at optical, UV, and GeV gamma-ray wavelengths at the time of the flare, although they are difficult to quantify precisely due to sparse coverage. A strong flare was seen at radio wavelengths roughly four months later, which might be related to the gamma-ray flaring activities. We discuss the implications of these multiwavelength results.},
  language  = {en}
}
@article{AhnenAnsoldiAntonellietal.2017,
  author    = {Ahnen, M. L. and Ansoldi, S. and Antonelli, L. A. and Antoranz, P. and Babic, A. and Banerjee, B. and Bangale, P. and de Almeida, U. Barres and Barrio, J. A. and Gonzalez, J. Becerra and Bednarek, W. and Bernardini, E. and Berti, A. and Biasuzzi, B. and Biland, A. and Blanch, O. and Bonnefoy, S. and Bonnoli, G. and Borracci, F. and Bretz, T. and Buson, S. and Carosi, A. and Chatterjee, A. and Clavero, R. and Colin, P. and Colombo, E. and Contreras, J. L. and Cortina, J. and Covino, S. and Da Vela, P. and Dazzi, F. and De Angelis, A. and De Lotto, B. and Wilhelmi, E. de Ona and Di Pierro, F. and Doert, M. and Dominguez, A. and Prester, D. Dominis and Dorner, D. and Doro, M. and Einecke, S. and Glawion, D. Eisenacher and Elsaesser, D. and Engelkemeier, M. and Ramazani, V. Fallah and Fernandez-Barral, A. and Fidalgo, D. and Fonseca, M. V. and Font, L. and Frantzen, K. and Fruck, C. and Galindo, D. and Lopez, R. J. Garcia and Garczarczyk, M. and Terrats, D. Garrido and Gaug, M. and Giammaria, P. and Godinovic, N. and Gonzalez Munoz, A. and Gora, D. and Guberman, D. and Hadasch, D. and Hahn, A. and Hanabata, Y. and Hayashida, M. and Herrera, J. and Hose, J. and Hrupec, D. and Hughes, G. and Idec, W. and Kodani, K. and Konno, Y. and Kubo, H. and Kushida, J. and La Barbera, A. and Lelas, D. and Lindfors, E. and Lombardi, S. and Longo, F. and Lopez, M. and Lopez-Coto, R. and Majumdar, P. and Makariev, M. and Mallot, K. and Maneva, G. and Manganaro, M. and Mannheim, K. and Maraschi, L. and Marcote, B. and Mariotti, M. and Martinez, M. and Mazin, D. and Menzel, U. and Miranda, J. M. and Mirzoyan, R. and Moralejo, A. and Moretti, E. and Nakajima, D. and Neustroev, V. and Niedzwiecki, A. and Rosillo, M. Nievas and Nilsson, K. and Nishijima, K. and Noda, K. and Nogues, L. and Overkemping, A. and Paiano, S. and Palacio, J. and Palatiello, M. and Paneque, D. and Paoletti, R. and Paredes, J. M. and Paredes-Fortuny, X. and Pedaletti, G. and Peresano, M. and Perri, L. and Persic, M. and Poutanen, J. and Moroni, P. G. Prada and Prandini, E. and Puljak, I. and Reichardt, I. and Rhode, W. and Ribo, M. and Rico, J. and Rodriguez Garcia, J. and Saito, T. and Satalecka, K. and Schroder, S. and Schultz, C. and Schweizer, T. and Shore, S. N. and Sillanpaa, A. and Sitarek, J. and Snidaric, I. and Sobczynska, D. and Stamerra, A. and Steinbring, T. and Strzys, M. and Suric, T. and Takalo, L. and Tavecchio, F. and Temnikov, P. and Terzic, T. and Tescaro, D. and Teshima, M. and Thaele, J. and Torres, D. F. and Toyama, T. and Treves, A. and Vanzo, G. and Verguilov, V. and Vovk, I. and Ward, J. E. and Will, M. and Wu, M. H. and Zanin, R. and Abeysekara, A. U. and Archambault, S. and Archer, A. and Benbow, W. and Bird, R. and Buchovecky, M. and Buckley, J. H. and Bugaev, V. and Connolly, M. P. and Cui, W. and Dickinson, H. J. and Falcone, A. and Feng, Q. and Finley, J. P. and Fleischhack, H. and Flinders, A. and Fortson, L. and Gillanders, G. H. and Griffin, S. and Grube, J. and Huetten, M. and Hanna, D. and Holder, J. and Humensky, T. B. and Kaaret, P. and Kar, P. and Kelley-Hoskins, N. and Kertzman, M. and Kieda, D. and Krause, M. and Krennrich, F. and Lang, M. J. and Maier, G. and McCann, A. and Moriarty, P. and Mukherjee, R. and Nieto, D. and Ong, R. A. and Otte, N. and Park, N. and Perkins, J. and Pichel, A. and Pohl, M. and Popkow, A. and Pueschel, Elisa and Quinn, J. and Ragan, K. and Reynolds, P. T. and Richards, G. T. and Roache, E. and Rovero, A. C. and Rulten, C. and Sadeh, I. and Santander, M. and Sembroski, G. H. and Shahinyan, K. and Telezhinsky, Igor O. and Tucci, J. V. and Tyler, J. and Wakely, S. P. and Weinstein, A. and Wilcox, P. and Wilhelm, Alina and Williams, D. A. and Zitzer, B. and Razzaque, S. and Villata, M. and Raiteri, C. M. and Aller, H. D. and Aller, M. F. and Larionov, V. M. and Arkharov, A. A. and Blinov, D. A. and Efimova, N. V. and Grishina, T. S. and Hagen-Thorn, V. A. and Kopatskaya, E. N. and Larionova, L. V. and Larionova, E. G. and Morozova, D. A. and Troitsky, I. S. and Ligustri, R. and Calcidese, P. and Berdyugin, A. and Kurtanidze, O. M. and Nikolashvili, M. G. and Kimeridze, G. N. and Sigua, L. A. and Kurtanidze, S. O. and Chigladze, R. A. and Chen, W. P. and Koptelova, E. and Sakamoto, T. and Sadun, A. C. and Moody, J. W. and Pace, C. and Pearson, R. and Yatsu, Y. and Mori, Y. and Carraminyana, A. and Carrasco, L. and de la Fuente, E. and Norris, J. P. and Smith, P. S. and Wehrle, A. and Gurwell, M. A. and Zook, A. and Pagani, C. and Perri, M. and Capalbi, M. and Cesarini, A. and Krimm, H. A. and Kovalev, Y. Y. and Kovalev, Yu. A. and Ros, E. and Pushkarev, A. B. and Lister, M. L. and Sokolovsky, K. V. and Kadler, M. and Piner, G. and Lahteenmaki, A. and Tornikoski, M. and Angelakis, E. and Krichbaum, T. P. and Nestoras, I. and Fuhrmann, L. and Zensus, J. A. and Cassaro, P. and Orlati, A. and Maccaferri, G. and Leto, P. and Giroletti, M. and Richards, J. L. and Max-Moerbeck, W. and Readhead, A. C. S.},
  title     = {Multiband variability studies and novel broadband SED modeling of Mrk 501 in 2009},
  series = {Astronomy and astrophysics : an international weekly journal},
  volume    = {603},
  journal   = {Astronomy and astrophysics : an international weekly journal},
  publisher = {EDP Sciences},
  address   = {Les Ulis},
  organization    = {MAGIC Collaboration;VERITAS Collaboration},
  issn      = {1432-0746},
  doi       = {10.1051/0004-6361/201629540},
  pages     = {30},
  year      = {2017},
  abstract  = {Aims. We present an extensive study of the BL Lac object Mrk 501 based on a data set collected during the multi-instrument campaign spanning from 2009 March 15 to 2009 August 1, which includes, among other instruments, MAGIC, VERITAS, Whipple 10 m, and Fermi-LAT to cover the gamma-ray range from 0.1 GeV to 20 TeV; RXTE and Swift to cover wavelengths from UV to hard X-rays; and GASP-WEBT, which provides coverage of radio and optical wavelengths. Optical polarization measurements were provided for a fraction of the campaign by the Steward and St. Petersburg observatories. We evaluate the variability of the source and interband correlations, the gamma-ray flaring activity occurring in May 2009, and interpret the results within two synchrotron self-Compton (SSC) scenarios. Methods. The multiband variability observed during the full campaign is addressed in terms of the fractional variability, and the possible correlations are studied by calculating the discrete correlation function for each pair of energy bands where the significance was evaluated with dedicated Monte Carlo simulations. The space of SSC model parameters is probed following a dedicated grid-scan strategy, allowing for a wide range of models to be tested and offering a study of the degeneracy of model-to-data agreement in the individual model parameters, hence providing a less biased interpretation than the "single-curve SSC model adjustment" typically reported in the literature. Results. We find an increase in the fractional variability with energy, while no significant interband correlations of flux changes are found on the basis of the acquired data set. The SSC model grid-scan shows that the flaring activity around May 22 cannot be modeled adequately with a one-zone SSC scenario (using an electron energy distribution with two breaks), while it can be suitably described within a two (independent) zone SSC scenario. Here, one zone is responsible for the quiescent emission from the averaged 4.5-month observing period, while the other one, which is spatially separated from the first, dominates the flaring emission occurring at X-rays and very-high-energy (> 100 GeV, VHE) gamma-rays. The flaring activity from May 1, which coincides with a rotation of the electric vector polarization angle (EVPA), cannot be satisfactorily reproduced by either a one-zone or a two-independent-zone SSC model, yet this is partially affected by the lack of strictly simultaneous observations and the presence of large flux changes on sub-hour timescales (detected at VHE gamma rays). Conclusions. The higher variability in the VHE emission and lack of correlation with the X-ray emission indicate that, at least during the 4.5-month observing campaign in 2009, the highest energy (and most variable) electrons that are responsible for the VHE gamma rays do not make a dominant contribution to the similar to 1 keV emission. Alternatively, there could be a very variable component contributing to the VHE gamma-ray emission in addition to that coming from the SSC scenario. The studies with our dedicated SSC grid-scan show that there is some degeneracy in both the one-zone and the two-zone SSC scenarios probed, with several combinations of model parameters yielding a similar model-to-data agreement, and some parameters better constrained than others. The observed gamma-ray flaring activity, with the EVPA rotation coincident with the first gamma-ray flare, resembles those reported previously for low frequency peaked blazars, hence suggesting that there are many similarities in the flaring mechanisms of blazars with different jet properties.},
  language  = {en}
}
@article{AbdoAckermannAjelloetal.2011,
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B. and Fortin, P. and Frailis, M. and Fuhrmann, L. and Fukazawa, Y. and Funk, S. and Fusco, P. and Gargano, F. and Gasparrini, D. and Gehrels, N. and Germani, S. and Giglietto, N. and Giordano, F. and Giroletti, M. and Glanzman, T. and Godfrey, G. and Grenier, I. A. and Guillemot, L. and Guiriec, S. and Hayashida, M. and Hays, E. and Horan, D. and Hughes, R. E. and Johannesson, G. and Johnson, A. S. and Johnson, W. N. and Kadler, M. and Kamae, T. and Katagiri, H. and Kataoka, J. and Knoedlseder, J. and Kuss, M. and Lande, J. and Latronico, L. and Lee, S. -H. and Lemoine-Goumard, M. and Longo, F. and Loparco, F. and Lott, B. and Lovellette, M. N. and Lubrano, P. and Madejski, G. M. and Makeev, A. and Max-Moerbeck, W. and Mazziotta, Mario Nicola and McEnery, J. E. and Mehault, J. and Michelson, P. F. and Mitthumsiri, W. and Mizuno, T. and Moiseev, A. A. and Monte, C. and Monzani, M. E. and Morselli, A. and Moskalenko, I. 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W. and Mori, Y. and Nestoras, I. and Orlati, A. and Pagani, C. and Pace, C. and Pearson, R. and Perri, M. and Piner, B. G. and Pushkarev, A. B. and Ros, E. and Sadun, A. C. and Sakamoto, T. and Tornikoski, M. and Yatsu, Y. and Zook, A.},
  title     = {Insights into the high-energy gamma-Ray emission of markarian 501 fromextensive multifrequency observations in the fermi era},
  series = {The astrophysical journal : an international review of spectroscopy and astronomical physics},
  volume    = {727},
  journal   = {The astrophysical journal : an international review of spectroscopy and astronomical physics},
  number    = {2},
  publisher = {IOP Publ. Ltd.},
  address   = {Bristol},
  organization    = {Fermi-LAT Collaboration, MAGIC Collaboration, VERITAS Collaboration},
  issn      = {0004-637X},
  doi       = {10.1088/0004-637X/727/2/129},
  pages     = {26},
  year      = {2011},
  abstract  = {We report on the gamma-ray activity of the blazar Mrk 501 during the first 480 days of Fermi operation. We find that the average Large Area Telescope (LAT) gamma-ray spectrum of Mrk 501 can be well described by a single power-law function with a photon index of 1.78 +/- 0.03. While we observe relatively mild flux variations with the Fermi-LAT (within less than a factor of two), we detect remarkable spectral variability where the hardest observed spectral index within the LAT energy range is 1.52 +/- 0.14, and the softest one is 2.51 +/- 0.20. These unexpected spectral changes do not correlate with the measured flux variations above 0.3 GeV. In this paper, we also present the first results from the 4.5 month long multifrequency campaign (2009 March 15-August 1) on Mrk 501, which included the Very Long Baseline Array (VLBA), Swift, RXTE, MAGIC, and VERITAS, the F-GAMMA, GASP-WEBT, and other collaborations and instruments which provided excellent temporal and energy coverage of the source throughout the entire campaign. The extensive radio to TeV data set from this campaign provides us with the most detailed spectral energy distribution yet collected for this source during its relatively low activity. The average spectral energy distribution of Mrk 501 is well described by the standard one-zone synchrotron self-Compton (SSC) model. In the framework of this model, we find that the dominant emission region is characterized by a size less than or similar to 0.1 pc (comparable within a factor of few to the size of the partially resolved VLBA core at 15-43 GHz), and that the total jet power (similar or equal to 10(44) erg s(-1)) constitutes only a small fraction (similar to 10(-3)) of the Eddington luminosity. The energy distribution of the freshly accelerated radiating electrons required to fit the time-averaged data has a broken power-law form in the energy range 0.3 GeV-10 TeV, with spectral indices 2.2 and 2.7 below and above the break energy of 20 GeV. We argue that such a form is consistent with a scenario in which the bulk of the energy dissipation within the dominant emission zone of Mrk 501 is due to relativistic, proton-mediated shocks. We find that the ultrarelativistic electrons and mildly relativistic protons within the blazar zone, if comparable in number, are in approximate energy equipartition, with their energy dominating the jet magnetic field energy by about two orders of magnitude.},
  language  = {en}
}