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The Violent Hard X-Ray Variability of Mrk 421 Observed by NuSTAR in 2013 April

Paliya, Vaidehi S. and Böttcher, Markus and Diltz, Chris and Stalin, C. S. and Sahayanathan, S. and Ravikumar, C. D. (2015) The Violent Hard X-Ray Variability of Mrk 421 Observed by NuSTAR in 2013 April. Astrophysical Journal, 811 (2). Art. No. 143. ISSN 0004-637X. doi:10.1088/0004-637X/811/2/143.

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The well-studied blazar Markarian 421 (Mrk 421, z = 0.031) was the subject of an intensive multi-wavelength campaign when it flared in 2013 April. The recorded X-ray and very high-energy (E > 100 GeV) γ-ray fluxes are the highest ever measured from this object. At the peak of the activity, it was monitored by the hard X-ray focusing telescope Nuclear Spectroscopic Telescope Array (NuSTAR) and the Swift X-Ray Telescope (XRT). In this work, we present a detailed variability analysis of NuSTAR and Swift-XRT observations of Mrk 421 during this flaring episode. We obtained the shortest flux doubling time of 14.01 ± 5.03 minutes, which is the shortest hard X-ray (3-79 keV) variability ever recorded from Mrk 421, and is on the order of the light-crossing time of the black hole's event horizon. A pattern of extremely fast variability events superposed on slowly varying flares is found in most of the NuSTAR observations. We suggest that these peculiar variability patterns may be explained by magnetic energy dissipation and reconnection in a fast-moving compact emission region within the jet. Based on the fast variability, we derive a lower limit on the magnetic field strength of B ≥ 0.73{δ }_1^(-2/3) {ν }_(19)^(1/3) G, where δ_1 is the Doppler factor in units of 10, and ν_(19) is the characteristic X-ray synchrotron frequency in units of 10^(19) Hz.

Item Type:Article
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Paliya, Vaidehi S.0000-0001-7774-5308
Stalin, C. S.0000-0002-4998-1861
Additional Information:© 2015. The American Astronomical Society. Received 2015 July 3; accepted 2015 August 25; published 2015 September 30. We are thankful to the referee for a constructive review of the manuscript. This research has made use of data, software, and/or web tools obtained from NASAs High Energy Astrophysics Science Archive Research Center (HEASARC), a service of the Goddard Space Flight Center and the Smithsonian Astrophysical Observatory. This research has also made use of the NuSTAR Data Analysis Software (NuSTARDAS) jointly developed by the ASI Science Data Center (ASDC, Italy) and the California Institute of Technology (Caltech, USA). This work has made use of light curves provided by the University of California, San Diego Center for Astrophysics and Space Sciences, X-ray Group (R.E. Rothschild, A.G. Markowitz, E.S. Rivers, and B.A. McKim), obtained at This work made use of data supplied by the UK Swift Science Data Centre at the University of Leicester. The work of M.B. is supported by the South African Research Chair Initiative (SARChI) of the Department of Science and Technology and the National Research Foundation9 of South Africa.
Subject Keywords:galaxies: active; galaxies: jets; quasars: individual (Mrk 421) ; X-rays: galaxies
Issue or Number:2
Record Number:CaltechAUTHORS:20160131-142700185
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Official Citation:Vaidehi S. Paliya et al 2015 ApJ 811 143
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:64108
Deposited By: Joy Painter
Deposited On:03 Feb 2016 20:43
Last Modified:10 Nov 2021 23:26

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