RT Journal Article T1 Spectral energy distribution of Markarian 501: quiescent state versus extreme outburst A1 Antoranz Canales, Pedro A1 Barrio Uña, Juan Abel A1 Contreras González, José Luis A1 Fonseca González, Mª Victoria A1 Miranda Pantoja, José Miguel A1 Nieto, Daniel AB The very high energy (VHE; E > 100 GeV) blazar Markarian 501 (Mrk 501) has a well-studied history of extreme spectral variability and is an excellent laboratory for studying the physical processes within the jets of active galactic nuclei. However, there are few detailed multiwavelength studies of Mrk 501 during its quiescent state, due to its low luminosity. A short-term multiwavelength study of Mrk 501 was coordinated in 2009 March, focusing around a multi-day observation with the Suzaku X-ray satellite and including gamma-ray data from VERITAS, MAGIC, and the Fermi Gamma-ray Space Telescope with the goal of providing a well-sampled multiwavelength baseline measurement of Mrk 501 in the quiescent state. The results of these quiescent-state observations are compared to the historically extreme outburst of 1997 April 16, with the goal of examining variability of the spectral energy distribution (SED) between the two states. The derived broadband SED shows the characteristic double-peaked profile. We find that the X-ray peak shifts by over two orders of magnitude in photon energy between the two flux states while the VHE peak varies little. The limited shift in the VHE peak can be explained by the transition to the Klein-Nishina (KN) regime. Synchrotron self-Compton models are matched to the data and the implied KN effects are explored. PB IOP Publishing SN 0004-637X YR 2011 FD 2011-02-01 LK https://hdl.handle.net/20.500.14352/43897 UL https://hdl.handle.net/20.500.14352/43897 LA eng NO Abdo, A. A., et al. 2010, ApJS, 188, 405.Abdo, A. A., et al. 2011, ApJ, 727, 129.Acciari, V. A., et al. (VERITAS Collaboration) 2008, ApJ, 679, 1427.Aharonian, F. 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We acknowledge the excellent work of the technical support staff at the Fred Lawrence Whipple Observatory and the collaborating institutions in the construction and operation of the instrument.The MAGIC Collaboration thanks the Instituto de Astrofisica de Canarias for the excellent working conditions at the Observatorio del Roque de los Muchachos in La Palma. The support of the German BMBF and MPG, the Italian INFN, the Swiss National Fund SNF, and the Spanish MICINN is gratefully acknowledged. This work was also supported by the Marie Curie program, by the CPAN CSD2007-00042 and MultiDark CSD2009-00064 projects of the Spanish Consolider-Ingenio 2010 program, by grant DO02-353 of the Bulgarian NSF, by grant 127740 of the Academy of Finland, by the YIP of the Helmholtz Gemeinschaft, by the DFG Cluster of Excellence "Origin and Structure of the Universe," and by the Polish MNiSzW Grant N N203 390834. NO INFN Padova NO German BMBF NO German MPG NO Italian INFN NO Swiss National Fund SNF NO Spanish MICINN NO NASA NO U.S. Department of Energy NO U.S. National Science Foundation NO Smithsonian Institution NO NSERC in Canada NO Science Foundation Ireland NO STFC in the UK DS Docta Complutense RD 7 may 2024