Refereed journal article or data article (A1)

A combined radio and GeV gamma-ray view of the 2012 and 2013 flares of Mrk 421




List of AuthorsT. Hovatta, M. Petropoulou, J. L. Richards, D. Giannios, K. Wiik, M. Baloković, A. Lähteenmäki, B. Lott, W. Max-Moerbeck, V. Ramakrishnan, A. C. S. Readhead

PublisherOXFORD UNIV PRESS

Publication year2015

JournalMonthly Notices of the Royal Astronomical Society

Journal name in sourceMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY

Journal acronymMON NOT R ASTRON SOC

Volume number448

Issue number4

Start page3121

End page3131

Number of pages11

ISSN0035-8711

DOIhttp://dx.doi.org/10.1093/mnras/stv220


Abstract

In 2012 Markarian 421 underwent the largest flare ever observed in this blazar at radio frequencies. In the present study, we start exploring this unique event and compare it to a less extreme event in 2013. We use 15 GHz radio data obtained with the Owens Valley Radio Observatory 40-m telescope, 95 GHz millimetre data from the Combined Array for Research in Millimeter-Wave Astronomy, and GeV gamma-ray data from the Fermi Gamma-ray Space Telescope. The radio light curves during the flaring periods in 2012 and 2013 have very different appearances, in both shape and peak flux density. Assuming that the radio and gamma-ray flares are physically connected, we attempt to model the most prominent sub-flares of the 2012 and 2013 activity periods by using the simplest possible theoretical framework. We first fit a one-zone synchrotron self-Compton (SSC) model to the less extreme 2013 flare and estimate parameters describing the emission region. We then model the major gamma-ray and radio flares of 2012 using the same framework. The 2012 gamma-ray flare shows two distinct spikes of similar amplitude, so we examine scenarios associating the radio flare with each spike in turn. In the first scenario, we cannot explain the sharp radio flare with a simple SSC model, but we can accommodate this by adding plausible time variations to the Doppler beaming factor. In the second scenario, a varying Doppler factor is not needed, but the SSC model parameters require fine-tuning. Both alternatives indicate that the sharp radio flare, if physically connected to the preceding gamma-ray flares, can be reproduced only for a very specific choice of parameters.



Last updated on 2021-24-06 at 10:20