A1 Refereed original research article in a scientific journal
Dissecting the long-term emission behaviour of the BL Lac object Mrk 421
Authors: Carnerero MI, Raiteri CM, Villata M, Acosta-Pulido JA, Larionov VM, Smith PS, D'Ammando F, Agudo I, Arevalo MJ, Bachev R, Barnes J, Boeva S, Bozhilov V, Carosati D, Casadio C, Chen WP, Damljanovic G, Eswaraiah E, Forne E, Gantchev G, Gomez JL, Gonzalez-Morales PA, Grinon-Marin AB, Grishina TS, Holden M, Ibryamov S, Joner MD, Jordan B, Jorstad SG, Joshi M, Kopatskaya EN, Koptelova E, Kurtanidze OM, Kurtanidze SO, Larionova EG, Larionova LV, Latev G, Lazaro C, Ligustri R, Lin HC, Marscher AP, Martinez-Lombilla C, McBreen B, Mihov B, Molina SN, Moody JW, Morozova DA, Nikolashvili MG, Nilsson K, Ovcharov E, Pace C, Panwar N, Yabar AP, Pearson RL, Pinna F, Protasio C, Rizzi N, Redondo-Lorenzo FJ, Rodriguez-Coira G, Ros JA, Sadun AC, Savchenko SS, Semkov E, Slavcheva-Mihova L, Smith N, Strigachev A, Troitskaya YV, Troitsky IS, Vasilyev AA, Vince O, Troitsky IS, Vasilyev AA, Vince O
Publisher: OXFORD UNIV PRESS
Publication year: 2017
Journal: Monthly Notices of the Royal Astronomical Society
Journal name in source: MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
Journal acronym: MON NOT R ASTRON SOC
Volume: 472
Issue: 4
First page : 3789
Last page: 3804
Number of pages: 16
ISSN: 0035-8711
DOI: https://doi.org/10.1093/mnras/stx2185
Self-archived copy’s web address: https://research.utu.fi/converis/portal/detail/Publication/27455334
We report on long-term multiwavelength monitoring of blazar Mrk 421 by the GLAST-AGILE Support Program of the Whole Earth Blazar Telescope (GASP-WEBT) collaboration and Steward Observatory, and by the Swift and Fermi satellites. We study the source behaviour in the period 2007-2015, characterized by several extreme flares. The ratio between the optical, X-ray and gamma-ray fluxes is very variable. The gamma-ray flux variations show a fair correlation with the optical ones starting from 2012. We analyse spectropolarimetric data and find wavelength-dependence of the polarization degree (P), which is compatible with the presence of the host galaxy, and no wavelength dependence of the electric vector polarization angle (EVPA). Optical polarimetry shows a lack of simple correlation between P and flux and wide rotations of the EVPA. We build broad-band spectral energy distributions with simultaneous near-infrared and optical data from the GASP-WEBT and ultraviolet and X-ray data from the Swift satellite. They show strong variability in both flux and X-ray spectral shape and suggest a shift of the synchrotron peak up to a factor of similar to 50 in frequency. The interpretation of the flux and spectral variability is compatible with jet models including at least two emitting regions that can change their orientation with respect to the line of sight.
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