The Great Markarian 421 Flare of February 2010: Multiwavelength variability and correlation studies
Creators: name: Abeysekara, A. U.
name: Benbow, W.
name: Bird, R.
name: Brill, A.
name: Brose, R.
name: Buchovecky, M.
name: Buckley, J. H.
name: Christiansen, J. L.
name: Chromey, A. J.
name: Daniel, M. K.
name: Dumm, J.
name: Falcone, A.
name: Feng, Q.
name: Finley, J. P.
name: Fortson, L.
name: Furniss, A.
name: Galante, N.
name: Gent, A.
name: Gillanders, G. H.
name: Giuri, C.
name: Gueta, O.
name: Hassan, T.
name: Hervet, O.
name: Holder, J.
name: Hughes, G.
name: Humensky, T. B.
name: Johnson, C. A.
name: Kaaret, P.
name: Kar, P.
name: Kelley-Hoskins, N.
name: Kertzman, M.
name: Kieda, D.
name: Krause, M.
name: Krennrich, F.
name: Kumar, S.
name: Lang, M. J.
name: Moriarty, P.
name: Mukherjee, R.
name: Nelson, T.
name: Nieto, D.
name: Nievas-Rosillo, M.
name: O'Brien, S.
name: Ong, R. A.
name: Otte, A. N.
name: Park, N.
name: Petrashyk, A.
name: Pichel, A.
name: Pohl, M.
name: Prado, R. R.
name: Pueschel, E.
name: Quinn, J.
name: Ragan, K.
name: Reynolds, P. T.
name: Richards, G. T.
name: Roache, E.
name: Rovero, A. C.
name: Rulten, C.
name: Sadeh, I.
name: Santander, M.
name: Sembroski, G. H.
name: Shahinyan, K.
name: Stevenson, B.
name: Sushch, I.
name: Tyler, J.
name: Vassiliev, V. V.
name: Wakely, S. P.
name: Weinstein, A.
name: Wells, R. M.
name: Wilcox, P.
name: Wilhelm, A.
name: Williams, D. A.
name: Zitzer, B.
name: Acciari, V. A.
name: Ansoldi, S.
name: Antonelli, L. A.
name: Engels, A. Arbet
name: Baack, D.
name: Babić, A.
name: Banerjee, B.
name: de Almeida, U. Barres
name: Barrio, J. A.
name: González, J. Becerra
name: Bednarek, W.
name: Bellizzi, L.
name: Bernardini, E.
name: Berti, A.
name: Besenrieder, J.
name: Bhattacharyya, W.
name: Bigongiari, C.
name: Biland, A.
name: Blanch, O.
name: Bonnoli, G.
name: Busetto, G.
name: Carosi, R.
name: Ceribella, G.
name: Chai, Y.
name: Cikota, S.
name: Colak, S. M.
name: Colin, U.
name: Colombo, E.
name: Contreras, J. L.
name: Cortina, J.
name: Covino, S.
name: D'Elia, V.
name: Da Vela, P.
name: Dazzi, F.
name: De Angelis, A.
name: De Lotto, B.
name: Delfino, M.
name: Delgado, J.
name: Di Pierro, F.
name: Espiñera, E. Do Souto
name: Prester, D. Dominis
name: Dorner, D.
name: Doro, M.
name: Einecke, S.
name: Elsaesser, D.
name: Ramazani, V. Fallah
name: Fattorini, A.
name: Fernández-Barral, A.
name: Ferrara, G.
name: Fidalgo, D.
name: Foffano, L.
name: Fonseca, M. V.
name: Font, L.
name: Fruck, C.
name: Galindo, D.
name: Gallozzi, S.
name: López, R. J. García
name: Garczarczyk, M.
name: Gasparyan, S.
name: Gaug, M.
name: Godinović, N.
name: Green, D.
name: Guberman, D.
name: Hadasch, D.
name: Hahn, A.
name: Herrera, J.
name: Hoang, J.
name: Hrupec, D.
name: Inoue, S.
name: Ishio, K.
name: Iwamura, Y.
name: Kubo, H.
name: Kushida, J.
name: Lamastra, A.
name: Lelas, D.
name: Leone, F.
name: Lindfors, E.
name: Lombardi, S.
name: Longo, F.
name: López, M.
name: López-Coto, R.
name: López-Oramas, A.
name: Fraga, B. Machado de Oliveira
name: Maggio, C.
name: Majumdar, P.
name: Makariev, M.
name: Mallamaci, M.
name: Maneva, G.
name: Manganaro, M.
name: Mannheim, K.
name: Maraschi, L.
name: Mariotti, M.
name: Martínez, M.
name: Masuda, S.
name: Mazin, D.
name: Miceli, D.
name: Minev, M.
name: Miranda, J. M.
name: Mirzoyan, R.
name: Molina, E.
name: Moralejo, A.
name: Morcuende, D.
name: Moreno, V.
name: Moretti, E.
name: Munar-Adrover, P.
name: Neustroev, V.
name: Niedzwiecki, A.
name: Rosillo, M. Nievas
name: Nigro, C.
name: Nilsson, K.
name: Ninci, D.
name: Nishijima, K.
name: Noda, K.
name: Nogués, L.
name: Nöthe, M.
name: Paiano, S.
name: Palacio, J.
name: Palatiello, M.
name: Paneque, D.
name: Paoletti, R.
name: Paredes, J. M.
name: Peñil, P.
name: Peresano, M.
name: Persic, M.
name: Moroni, P. G. Prada
name: Prandini, E.
name: Puljak, I.
name: Rhode, W.
name: Ribó, M.
name: Rico, J.
name: Righi, C.
name: Rugliancich, A.
name: Saha, L.
name: Sahakyan, N.
name: Saito, T.
name: Satalecka, K.
name: Schweizer, T.
name: Sitarek, J.
name: Šnidarić, I.
name: Sobczynska, D.
name: Somero, A.
name: Stamerra, A.
name: Strom, D.
name: Strzys, M.
name: Sun, S.
name: Surić, T.
name: Tavecchio, F.
name: Temnikov, P.
name: Terzić, T.
name: Teshima, M.
name: Torres-Albà, N.
name: Tsujimoto, S.
name: van Scherpenberg, J.
name: Vanzo, G.
name: Acosta, M. Vazquez
name: Vovk, I.
name: Will, M.
name: Zarić, D.
name: Aller, H. D.
name: Aller, M. F.
name: Carini, M. T.
name: Horan, D.
name: Jordan, B.
name: Jorstad, Svetlana G.
name: Kurtanidze, O. M.
name: Kurtanidze, S. O.
name: Lähteenmäki, A.
name: Larionov, V. M.
name: Larionova, E. G.
name: Madejski, G.
name: Marscher, Alan P.
name: Max-Moerbeck, W.
name: Moody, J. Ward
name: Morozova, D. A.
name: Nikolashvili, M. G.
name: Raiteri, C. M.
name: Readhead, A. C. S.
name: Richards, J. L.
name: Sadun, Alberto C.
name: Sakamoto, T.
name: Sigua, L. A.
name: Smith, P. S.
name: Talvikki, H.
name: Tammi, J.
name: Tornikoski, M.
name: Troitsky, I. S.
name: Villata, M.
Publisher: name: arXiv
Year: 2020
Subjects: subject: High Energy Astrophysical Phenomena (astro-ph.HE)
subject: FOS: Physical sciences
subject: FOS: Physical sciences

description: We report on variability and correlation studies using multiwavelength observations of the blazar Mrk 421 during the month of February, 2010 when an extraordinary flare reaching a level of $\sim$27~Crab Units above 1~TeV was measured in very-high-energy (VHE) $γ$-rays with the VERITAS observatory. This is the highest flux state for Mrk 421 ever observed in VHE $γ$-rays. Data are analyzed from a coordinated campaign across multiple instruments including VHE $γ$-ray (VERITAS, MAGIC), high-energy (HE) $γ$-ray (Fermi-LAT), X-ray (Swift}, RXTE, MAXI), optical (including the GASP-WEBT collaboration and polarization data) and radio (Metsähovi, OVRO, UMRAO). Light curves are produced spanning multiple days before and after the peak of the VHE flare, including over several flare `decline' epochs. The main flare statistics allow 2-minute time bins to be constructed in both the VHE and optical bands enabling a cross-correlation analysis that shows evidence for an optical lag of $\sim$25-55 minutes, the first time-lagged correlation between these bands reported on such short timescales. Limits on the Doppler factor ($δ\gtrsim 33$) and the size of the emission region ($ δ^{-1}R_B \lesssim 3.8\times 10^{13}\,\,\mbox{cm}$) are obtained from the fast variability observed by VERITAS during the main flare. Analysis of 10-minute-binned VHE and X-ray data over the decline epochs shows an extraordinary range of behavior in the flux-flux relationship: from linear to quadratic to lack of correlation to anti-correlation. Taken together, these detailed observations of an unprecedented flare seen in Mrk 421 are difficult to explain by the classic single-zone synchrotron self-Compton model.
description: 41 pages including 3 appendices, 13 figures; version accepted to Astrophysical Journal