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By Markus Ackermann, Marco Ajello, Jean Ballet, Guido Barbiellini, D. Bastieri, R. Bellazzini, R. D. Blandford, E. D. Bloom, E. Bonamente, A. W. Borgland, E. Bottacini, J. Bregeon, M. Brigida, P. Bruel, R. Buehler, S. Buson, G. A. Caliandro, R. A. Cameron, P. A. Caraveo, J. M. Casandjian, E. Cavazzuti, C. Cecchi, E. Charles, A. Chekhtman, J. Chiang, S. Ciprini, R. Claus, J. Cohen-Tanugi, S. Cutini, F. D'Ammando, F. De Palma, C. D. Dermer, E. Do Couto E Silva, P. S. Drell, A. Drlica-Wagner, R. Dubois, C. Favuzzi, S. J. Fegan, E. C. Ferrara, W. B. Focke, P. Fortin, L. Fuhrmann, Y. Fukazawa, P. Fusco, F. Gargano, D. Gasparrini, N. Gehrels, S. Germani, N. Giglietto, P. Giommi, F. Giordano, M. Giroletti, T. Glanzman, G. Godfrey, I. A. Grenier, S. Guiriec, D. Hadasch, M. Hayashida, R. E. Hughes, R. Itoh, G. Jóhannesson, A. S. Johnson, H. Katagiri, J. Kataoka, J. Knödlseder, M. Kuss, J. Lande, S. Larsson, S.-H. Lee, F. Longo, F. Loparco, B. Lott, M. N. Lovellette, P. Lubrano, G. M. Madejski, M. N. Mazziotta, J. E. Mcenery, J. Mehault, P. F. Michelson, W. Mitthumsiri, T. Mizuno, C. Monte, M. E. Monzani, A. Morselli, I. V. Moskalenko, S. Murgia, M. Naumann-Godo, S. Nishino, J. P. Norris, E. Nuss, T. Ohsugi, A. Okumura, N. Omodei, E. Orlando, M. Ozaki, D. Paneque, J. H. Panetta, V. Pelassa, M. Pesce-Rollins, M. Pierbattista, F. Piron, G. Pivato, T.A. Porter, S. Rainò, R. Rando, D. Rastawicki, M. Razzano, A. Readhead, A. Reimer, O. Reimer, L. C. Reyes, J. L. Richards, C. Sbarra, C. Sgrò, E. J. Siskind, G. Spandre, P. Spinelli, A. Szostek, H. Takahashi, T. Tanaka, J. G. Thayer, J. B. Thayer, D. J. Thompson, M. Tinivella, D. F. Torres, G. Tosti, E. Troja, T. L. Usher, J. Vandenbroucke, V. Vasileiou, G. Vianello, V. Vitale, A. P. Waite, B. L. Winer, K. S. Wood, Z. Yang, S. Zimmer, R. Moderski, K. Nalewajko, M. Sikora, M. Villata, C. M. Raiteri, H. D. Aller, M. F. Aller, A. A. Arkharov, E. Benítez, A. Berdyugin, D.A. Blinov, M. Boettcher, O. J. A. Bravo Calle, C. S. Buemi, D. Carosati, W. P. Chen, C. Diltz, A. Di Paola, M. Dolci, N. V. Efimova, E. Forné, M. A. Gurwell, J. Heidt, D. Hiriart, B. Jordan, G. Kimeridze, T. S. Konstantinova, E. N. Kopatskaya, E. Koptelova, O. M. Kurtanidze, A. Lähteenmäki, E. G. Larionova, L. V. Larionova, V. M. Larionov, P. Leto, E. Lindfors, H. C. Lin, D.A. Morozova, M. G. Nikolashvili, K. Nilsson, M. Oksman, P. Roustazadeh, A. Sievers, L. A. Sigua, A. Sillanpää, T. Takahashi, L. O. Takalo, M. Tornikoski, C. Trigilio, I. S. Troitsky, G. Umana, E. Angelakis, T. P. Krichbaum, I. Nestoras, D. Riquelme, M. Krips, S. Trippe, A. Arai, K. S. Kawabata, K. Sakimoto, M. Sasada, S. Sato, M. Uemura, M. Yamanaka, M. Yoshida, T. Belloni, G. Tagliaferri, E. W. Bonning, J. Isler, C. M. Urry, E. Hoversten, A. Falcone, C. Pagani and M. Stroh


The blazar AO 0235+164 (z = 0.94) has been one of the most active objects observed by Fermi Large Area Telescope (LAT) since its launch in Summer 2008. In addition to the continuous coverage by Fermi, contemporaneous observations were carried out from the radio to γ-ray bands between 2008 September and 2009 February. In this paper, we summarize the rich multi-wavelength data collected during the campaign (including F-GAMMA, GASP-WEBT, Kanata, OVRO, RXTE, SMARTS, Swift, and other instruments), examine the cross-correlation between the light curves measured in the different energy bands, and interpret the resulting spectral energy distributions in the context of well-known blazar emission models. We find that the γ-ray activity is well correlated with a series of near-IR/optical flares, accompanied by an increase in the optical polarization degree. On the other hand, the X-ray light curve shows a distinct 20 day high state of unusually soft spectrum, which does not match the extrapolation of the optical/UV synchrotron spectrum. We tentatively interpret this feature as the bulk Compton emission by cold electrons contained in the jet, which requires an accretion disk corona with an effective covering factor of 19% at a distance of 100 R g. We model the broadband spectra with a leptonic model with external radiation dominated by the infrared emission from the dusty torus

Topics: BL Lacertae objects: individual (AO 0235+164), galaxies: active, galaxies: jets, gamma rays: galaxies, radiation mechanisms: non-thermal, [ PHYS.ASTR.HE ] Physics [physics]/Astrophysics [astro-ph]/High Energy Astrophysical Phenomena [astro-ph.HE], [ SDU.ASTR.HE ] Sciences of the Universe [physics]/Astrophysics [astro-ph]/High Energy Astrophysical Phenomena [astro-ph.HE]
Publisher: American Astronomical Society
Year: 2012
DOI identifier: 10.1088/0004-637X
OAI identifier: oai:HAL:in2p3-00769591v1
Provided by: Hal-Diderot
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