Swift Observations of Mrk 421 in Selected Epochs. I. The Spectral and Flux Variability in 2005-2008
Journal
Date Issued
2018
Author(s)
Kapanadze, B.
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•
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Hughes, P.
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Aller, M.
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Aller, H.
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Kharshiladze, O.
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Kapanadze, S.
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Tabagari, L.
Abstract
We present detailed results of Swift observations of the nearby TeV-detected blazar Mrk 421, based on the rich archival data obtained during 2005 March-2008 June. The best fits of the 0.3-10 keV spectra were mainly obtained using the log-parabolic model, yielding low spectral curvatures expected in the case of the efficient stochastic acceleration of particles. During strong X-ray flares, the position of the synchrotron spectral energy distribution peak {E}{{p}} was beyond 8 keV for 41 spectra, while it sometimes was situated at the UV frequencies in quiescent states. The photon index at 1 keV exhibited a broad range, and the values a< 1.70 were observed during the strong flares, hinting at the possible presence of a jet hadronic component. The spectral parameters were correlated in some periods, expected in the framework of the first- and second-order Fermi accelerations of X-ray emitting particles, as well as in the case of turbulence spectrum. The 0.3-10 keV flux and spectral parameters sometimes showed very fast variability down to the fluctuations by 6-20% in 180-960 s, possibly related to the small-scale turbulent areas containing strongest magnetic fields. X-ray and very high-energy fluxes often showed correlated variability, although several occurrences of more complicated variability patterns are also revealed, indicating that the multifrequency emission of Mrk 421 could not be generated in a single zone.
Volume
854
Issue
1
Start page
66
Issn Identifier
0004-637X
Ads BibCode
2018ApJ...854...66K
Rights
open.access
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