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Title: A combined radio and GeV γ-ray view of the 2012 and 2013 flares of Mrk 421

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 γ-ray data from the Fermi Gamma-ray Space Telescope. Here, 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 γ-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 γ-ray and radio flares of 2012 using the same framework. The 2012 γ-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 sharpmore » 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 γ-ray flares, can be reproduced only for a very specific choice of parameters.« less

Authors:
 [1];  [2];  [2];  [2];  [3];  [4];  [5];  [6];  [7];  [8];  [4]
  1. Aalto Univ. Metsahovi Radio Observatory, Kylmala (Finland); California Inst. of Technology (CalTech), Pasadena, CA (United States)
  2. Purdue Univ., West Lafayette, IN (United States)
  3. Univ. of Turku, Piikkio (Finland)
  4. California Inst. of Technology (CalTech), Pasadena, CA (United States)
  5. Aalto Univ. Metsahovi Radio Observatory, Kylmala (Finland); Aalto Univ. (Finland). Dept. of Radio Science and Engineering
  6. Univ. Bordeaux, Gradignan (France); CNRS, IN2P3, CENBG, Gradignan (France)
  7. National Radio Astronomy Observatory, Socorro, NM (United States)
  8. Aalto Univ. Metsahovi Radio Observatory, Kylmala (Finland)
Publication Date:
Research Org.:
SLAC National Accelerator Lab., Menlo Park, CA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1355165
Grant/Contract Number:
AC02-76SF00515
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Monthly Notices of the Royal Astronomical Society
Additional Journal Information:
Journal Volume: 448; Journal Issue: 4; Journal ID: ISSN 0035-8711
Publisher:
Royal Astronomical Society
Country of Publication:
United States
Language:
English
Subject:
79 ASTRONOMY AND ASTROPHYSICS; galaxies: active; BL Lacertae objects: individual: Markarian 421; galaxies: jets

Citation Formats

Hovatta, Talvikki, Petropoulou, M., Richards, J. L., Giannios, D., Wiik, K., Balokovi , M., Lahteenmaki, A., Lott, B., Max-Moerbeck, W., Ramakrishnan, V., and Readhead, A. C. S. A combined radio and GeV γ-ray view of the 2012 and 2013 flares of Mrk 421. United States: N. p., 2015. Web. doi:10.1093/mnras/stv220.
Hovatta, Talvikki, Petropoulou, M., Richards, J. L., Giannios, D., Wiik, K., Balokovi , M., Lahteenmaki, A., Lott, B., Max-Moerbeck, W., Ramakrishnan, V., & Readhead, A. C. S. A combined radio and GeV γ-ray view of the 2012 and 2013 flares of Mrk 421. United States. doi:10.1093/mnras/stv220.
Hovatta, Talvikki, Petropoulou, M., Richards, J. L., Giannios, D., Wiik, K., Balokovi , M., Lahteenmaki, A., Lott, B., Max-Moerbeck, W., Ramakrishnan, V., and Readhead, A. C. S. Mon . "A combined radio and GeV γ-ray view of the 2012 and 2013 flares of Mrk 421". United States. doi:10.1093/mnras/stv220. https://www.osti.gov/servlets/purl/1355165.
@article{osti_1355165,
title = {A combined radio and GeV γ-ray view of the 2012 and 2013 flares of Mrk 421},
author = {Hovatta, Talvikki and Petropoulou, M. and Richards, J. L. and Giannios, D. and Wiik, K. and Balokovi , M. and Lahteenmaki, A. and Lott, B. and Max-Moerbeck, W. and Ramakrishnan, V. and Readhead, A. C. S.},
abstractNote = {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 γ-ray data from the Fermi Gamma-ray Space Telescope. Here, 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 γ-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 γ-ray and radio flares of 2012 using the same framework. The 2012 γ-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 γ-ray flares, can be reproduced only for a very specific choice of parameters.},
doi = {10.1093/mnras/stv220},
journal = {Monthly Notices of the Royal Astronomical Society},
number = 4,
volume = 448,
place = {United States},
year = {Mon Mar 09 00:00:00 EDT 2015},
month = {Mon Mar 09 00:00:00 EDT 2015}
}

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