Long-term multi-wavelength variability and correlation study of Markarian 421 from 2007 to 2009

/ Authors

M. L. Ahnen, S. Ansoldi, L. A. Antonelli, P. Antoranz, A. Babić, B. Banerjee, P. Bangale, U. D. Almeida, J. Barrio, J. Gonz'alez

and 321 more authors

W. Bednarek, E. Bernardini, B. Biasuzzi, A. Biland, O. Blanch, S. Bonnefoy, G. Bonnoli, F. Borracci, T. Bretz, S. Buson, A. Carosi, A. Chatterjee, R. Clavero, P. Colin, E. Colombo, J. Contreras, J. Cortina, S. Covino, P. D. Vela, F. Dazzi, A. Angelis, B. Lotto, E. O. Wilhelmi, F. Pierro, A. Domínguez, D. Prester, D. Dorner, M. Doro, S. Einecke, D. Glawion, D. Elsaesser, A. Fern'andez-Barral, D. Fidalgo, M. Fonseca, L. Font, K. Frantzen, C. Fruck, D. Galindo, R. L'opez, M. Garczarczyk, D. G. Terrats, M. Gaug, P. Giammaria, N. Godinovi'c, A. G. Muñoz, D. Góra, D. Guberman, D. Hadasch, A. Hahn, Y. Hanabata, M. Hayashida, J. Herrera, J. Hose, D. Hrupec, G. Hughes, W. Idec, K. Kodani, Y. Konno, H. Kubo, J. Kushida, A. Barbera, D. Lelas, E. Lindfors, S. Lombardi, F. Longo, M. L'opez, R. L'opez-Coto, P. Majumdar, M. Makariev, K. Mallot, G. Maneva, M. Manganaro, K. Mannheim, L. Maraschi, B. Marcote, M. Mariotti, M. Mart'inez, D. Mazin, U. Menzel, J. Miranda, R. Mirzoyan, A. Moralejo, E. Moretti, D. Nakajima, V. Neustroev, A. Niedźwiecki, M. Rosillo, K. Nilsson, K. Nishijima, K. Noda, L. Nogu'es, R. Orito, A. Overkemping, S. Paiano, J. Palacio, M. Palatiello, D. Paneque, R. Paoletti, J. Paredes, X. Paredes-Fortuny, G. Pedaletti, L. Perri, M. Persic, J. Poutanen, P. Moroni, E. Prandini, I. Puljak, W. Rhode, M. Rib'o, J. Rico, J. Garcia, T. Saito, K. Satalecka, C. Schultz, T. Schweizer, S. Shore, A. Sillanpaa, J. Sitarek, I. Šnidarić, D. Sobczynska, A. Stamerra, T. Steinbring, M. Strzys, L. Takalo, H. Takami, F. Tavecchio, P. Temnikov, T. Terzi'c, D. Tescaro, M. Teshima, J. Thaele, D. Torres, T. Toyama, A. Treves, V. Verguilov, I. Vovk, J. Ward, M. Will, M. H. Wu, R. Zanin, D. Blinov, W. P. Chen, N. Efimova, E. Forn'e, T. Grishina, T. Hovatta, B. Jordan, G. Kimeridze, E. Kopatskaya, E. Koptelova, O. Kurtanidze, S. O. Kurtanidze, A. Lahteenmaaki, V. Larionov, E. Larionova, L. Larionova, R. Ligustri, H. C. Lin, B. Mcbreen, D. Morozova, M. Nikolashvili, C. Raiteri, J. A. Ros, A. Sadun, L. Sigua, M. Tornikoski, I. Troitsky, M. V. E. Zurich, CH-8093 Zurich, Switzerland., U. Udine, I. Trieste, I. Udine, Italy., I. I. F. Astrophysics, I. Rome, U. Siena, I. Pisa, I. Siena, Croatian Magic Consortium, Rudjer Boskovic Institute, University of Rijeka, University of Split, U. Zagreb, Croatia., S. S. I. O. Physics, 1. Bidhannagar, Salt Lake, Sector-1, Kolkata 700064, India., M. F. Physik, D-80805 Munchen, H Germany, U. Complutense, E. Madrid, Spain., Instituto de Astrof'isica de Canarias, E. Laguna, Tenerife, U. L. Laguna, D. Astrof'isica, E. Laguna, University of L'od'z, PL-90236 Lodz, Poland, D. Elektronen-Synchrotron, D. Zeuthen, Institut de F'isica d'Altes Energies, T. Z. F. O. Science, Technology, Campus Uab, 08193 Bellaterra, U. Wurzburg, D-97074 Wurzburg, U. Padova, Infn, I-35131 Padova, Institute for Space Sciences, E. Barcelona, Technische Universitat Dortmund, D. Dortmund, Unitat de F'isica de les Radiacions, Departament de F'isica, CERES-IEEC, U. Barcelona, E-08193 Bellaterra, U. Barcelona, Icc, IEEC-UB, E. Barcelona, Japanese Magic Consortium, Icrr, T. U. O. Tokyo, D. Physics, Hakubi Center, Kyoto University, T. University, The University of Tokushima, Kek, Japan., Finnish Magic Consortium, T. Observatory, U. Turku, A. Division, U. Oulu, Finland., Inst. for Nucl. Research, Nucl. Energy, BG-1784 Sofia, Bulgaria., U. Pisa, I. Pisa, Icrea, Now at Centro Brasileiro de Pesquisas F'isicas, R. Sigaud, 150 - Urca, RJ RiodeJaneiro-, 22290-180, Brazil, now at Nasa Goddard Space Flight Center, Greenbelt, MD 20771, Usa, D. O. Astronomy, U. Maryland, College Park, MD 20742, H. Berlin, 15 InstitutfurPhysikNewtonstr., 12489 Berlin Germany, N. C. E. P. F. D. Lausanne, Lausanne, also at Japanese Magic Consortium, N. Eso, Turku, also at INAF-Trieste, A. M. C. F. Astrophysics, 1290, Versoix, Astron. Inst., S. Univ., Russia., U. Crete, Heraklion, Greece., G. I. O. Astronomy, National Central University, 300 Zhongda Rd, Zhongli 32001, Tao-yuan, Taiwan, P. Observatory, St.-Petersburg, Agrupaci'o Astronomica de Sabadell, A. L. M. R. Observatory, Metsahovintie 114, FI-02540 Kylmala, S. O. Physics, Dublin Institute for Advanced Studies, Ireland, A. Observatory, Mt. Kanobili, 0301 Abastumani, Georgia, E. A. Observatory, Kazan Federal University, Tatarstan, Aalto University Department of Radio Science, Engineering, P. 13000, FI-00076 Aalto, Circolo Astrofili Talmassons, S. O. Physics, University College Dublin, Belfield, 4. Dublin, I. Torino, 1. P. Torinese, U. Colorado, Denver

/ Abstract

We study the multi-band variability and correlations of the TeV blazar Mrk 421 on year time scales, which can bring additional insight on the processes responsible for its broadband emission. We observed Mrk 421 in the very high energy (VHE) gamma-ray range with the Cherenkov telescope MAGIC-I from March 2007 to June 2009 for a total of 96 hours of effective time after quality cuts. The VHE flux variability is quantified with several methods, including the Bayesian Block algorithm, which is applied to data from Cherenkov telescopes for the first time. The 2.3 year long MAGIC light curve is complemented with data from the Swift/BAT and RXTE/ASM satellites and the KVA, GASP-WEBT, OVRO, and Metsahovi telescopes from February 2007 to July 2009, allowing for an excellent characterisation of the multi-band variability and correlations over year time scales. Mrk 421 was found in different gamma-ray emission states during the 2.3 year long observation period. Flares and different levels of variability in the gamma-ray light curve could be identified with the Bayesian Block algorithm. The same behaviour of a quiet and active emission was found in the X-ray light curves measured by Swift/BAT and the RXTE/ASM, with a direct correlation in time. The behaviour of the optical light curve of GASP-WEBT and the radio light curves by OVRO and Metsahovi are different as they show no coincident features with the higher energetic light curves and a less variable emission. The fractional variability is overall increasing with energy. The comparable variability in the X-ray and VHE bands and their direct correlation during both high- and low-activity periods spanning many months show that the electron populations radiating the X-ray and gamma-ray photons are either the same, as expected in the Synchrotron-Self-Compton mechanism, or at least strongly correlated, as expected in electromagnetic cascades.

Journal: arXiv: Astrophysics of Galaxies

DOI: 10.1051/0004-6361/201628447