The 2009 multiwavelength campaign on Mrk 421: Variability and correlation studies
Creators: name: MAGIC Collaboration
name: Aleksić, J.
name: Ansoldi, S.
name: Antonelli, L. A.
name: Antoranz, P.
name: Babic, A.
name: Bangale, P.
name: de Almeida, U. Barres
name: Barrio, J. A.
name: González, J. Becerra
name: Bednarek, W.
name: Berger, K.
name: Bernardini, E.
name: Biland, A.
name: Blanch, O.
name: Bock, R. K.
name: Bonnefoy, S.
name: Bonnoli, G.
name: Borracci, F.
name: Bretz, T.
name: Carmona, E.
name: Carosi, A.
name: Fidalgo, D. Carreto
name: Colin, P.
name: Colombo, E.
name: Contreras, J. L.
name: Cortina, J.
name: Covino, S.
name: Da Vela, P.
name: Dazzi, F.
name: De Angelis, A.
name: De Caneva, G.
name: De Lotto, B.
name: Mendez, C. Delgado
name: Doert, M.
name: Domínguez, A.
name: Prester, D. Dominis
name: Dorner, D.
name: Doro, M.
name: Einecke, S.
name: Eisenacher, D.
name: Elsaesser, D.
name: Farina, E.
name: Ferenc, D.
name: Fonseca, M. V.
name: Font, L.
name: Frantzen, K.
name: Fruck, C.
name: López, R. J. García
name: Garczarczyk, M.
name: Terrats, D. Garrido
name: Gaug, M.
name: Giavitto, G.
name: Godinović, N.
name: noz, A. González Mu\
name: Gozzini, S. R.
name: Hadamek, A.
name: Hadasch, D.
name: Herrero, A.
name: Hildebrand, D.
name: Hose, J.
name: Hrupec, D.
name: Idec, W.
name: Kadenius, V.
name: Kellermann, H.
name: Knoetig, M. L.
name: Krause, J.
name: Kushida, J.
name: La Barbera, A.
name: Lelas, D.
name: Lewandowska, N.
name: Lindfors, E.
name: Longo, F.
name: Lombardi, S.
name: López, M.
name: López-Coto, R.
name: López-Oramas, A.
name: Lorenz, E.
name: Lozano, I.
name: Makariev, M.
name: Mallot, K.
name: Maneva, G.
name: Mankuzhiyil, N.
name: Mannheim, K.
name: Maraschi, L.
name: Marcote, B.
name: Mariotti, M.
name: Martínez, M.
name: Mazin, D.
name: Menzel, U.
name: Meucci, M.
name: Miranda, J. M.
name: Mirzoyan, R.
name: Moralejo, A.
name: Munar-Adrover, P.
name: Nakajima, D.
name: Niedzwiecki, A.
name: Nilsson, K.
name: Nowak, N.
name: Orito, R.
name: Overkemping, A.
name: Paiano, S.
name: Palatiello, M.
name: Paneque, D.
name: Paoletti, R.
name: Paredes, J. M.
name: Paredes-Fortuny, X.
name: Partini, S.
name: Persic, M.
name: Prada, F.
name: Moroni, P. G. Prada
name: Prandini, E.
name: Preziuso, S.
name: Puljak, I.
name: Reinthal, R.
name: Rhode, W.
name: Ribó, M.
name: Rico, J.
name: Garcia, J. Rodriguez
name: Rügamer, S.
name: Saggion, A.
name: Saito, K.
name: Salvati, M.
name: Satalecka, K.
name: Scalzotto, V.
name: Scapin, V.
name: Schultz, C.
name: Schweizer, T.
name: Shore, S. N.
name: Sillanpää, A.
name: Sitarek, J.
name: Snidaric, I.
name: Sobczynska, D.
name: Spanier, F.
name: Stamatescu, V.
name: Stamerra, A.
name: Steinbring, T.
name: Storz, J.
name: Sun, S.
name: Surić, T.
name: Takalo, L.
name: Tavecchio, F.
name: Temnikov, P.
name: Terzić, T.
name: Tescaro, D.
name: Teshima, M.
name: Thaele, J.
name: Tibolla, O.
name: Torres, D. F.
name: Toyama, T.
name: Treves, A.
name: Uellenbeck, M.
name: Vogler, P.
name: Wagner, R. M.
name: Zandanel, F.
name: Zanin, R.
name: collaboration, VERITAS
name: :
name: Archambault, S.
name: Behera, B.
name: Beilicke, M.
name: Benbow, W.
name: Bird, R.
name: Buckley, J. H.
name: Bugaev, V.
name: Cerruti, M.
name: Chen, X.
name: Ciupik, L.
name: Collins-Hughes, E.
name: Cui, W.
name: Dumm, J.
name: Eisch, J. D.
name: Falcone, A.
name: Federici, S.
name: Feng, Q.
name: Finley, J. P.
name: Fleischhack, H.
name: Fortin, P.
name: Fortson, L.
name: Furniss, A.
name: Griffin, S.
name: Griffiths, S. T.
name: Grube, J.
name: Gyuk, G.
name: Hanna, D.
name: Holder, J.
name: Hughes, G.
name: Humensky, T. B.
name: Johnson, C. A.
name: Kaaret, P.
name: Kertzman, M.
name: Khassen, Y.
name: Kieda, D.
name: Krawczynski, H.
name: Krennrich, F.
name: Kumar, S.
name: Lang, M. J.
name: Maier, G.
name: McArthur, S.
name: Meagher, K.
name: Moriarty, P.
name: Mukherjee, R.
name: Ong, R. A.
name: Otte, A. N.
name: Park, N.
name: Pichel, A.
name: Pohl, M.
name: Popkow, A.
name: Prokoph, H.
name: Quinn, J.
name: Ragan, K.
name: Rajotte, J.
name: Reynolds, P. T.
name: Richards, G. T.
name: Roache, E.
name: Rovero, A. C.
name: Sembroski, G. H.
name: Shahinyan, K.
name: Staszak, D.
name: Telezhinsky, I.
name: Theiling, M.
name: Tucci, J. V.
name: Tyler, J.
name: Varlotta, A.
name: Wakely, S. P.
name: Weekes, T. C.
name: Weinstein, A.
name: Welsing, R.
name: Wilhelm, A.
name: Williams, D. A.
name: Zitzer, B.
name: collaborators, External
name: :
name: Villata, M.
name: Raiteri, C.
name: Aller, H. D.
name: Aller, M. F.
name: Chen, W. P.
name: Jordan, B.
name: Koptelova, E.
name: Kurtanidze, O. M.
name: Lähteenmäki, A.
name: McBreen, B.
name: Larionov, V. M.
name: Lin, C. S.
name: Nikolashvili, M. G.
name: Angelakis, E.
name: Capalbi, M.
name: nana, A. Carrami\
name: Carrasco, L.
name: Cassaro, P.
name: Cesarini, A.
name: Fuhrmann, L.
name: Giroletti, M.
name: Hovatta, T.
name: Krichbaum, T. P.
name: Krimm, H. A.
name: Max-Moerbeck, W.
name: Moody, J. W.
name: Maccaferri, G.
name: Mori, Y.
name: Nestoras, I.
name: Orlati, A.
name: Pace, C.
name: Pearson, R.
name: Perri, M.
name: Readhead, A. C. S.
name: Richards, J. L.
name: Sadun, A. C.
name: Sakamoto, T.
name: Tammi, J.
name: Tornikoski, M.
name: Yatsu, Y.
name: Zook, A.
Publisher: name: arXiv
Year: 2015
Subjects: subject: High Energy Astrophysical Phenomena (astro-ph.HE)
subject: FOS: Physical sciences
subject: FOS: Physical sciences

description: We performed a 4.5-month multi-instrument campaign (from radio to VHE gamma rays) on Mrk421 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. 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. The harder-when-brighter behavior in the X-ray spectra and the measured positive X-ray/VHE correlation during the 2009 multi-wavelength 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 Mrk421 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.
description: Accepted for publication in A&amp;A, 18 pages, 14 figures (v2 has a small modification in the acknowledgments, and also corrects a typo in the field "author" in the metadata)