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http://hdl.handle.net/20.500.12386/25876
Titolo: | X-Ray Flaring Activity of MRK 421 in the First Half of 2013 | Autori: | Kapanadze, B. Dorner, D. VERCELLONE, STEFANO ROMANO, Patrizia Aller, H. Aller, M. Hughes, P. Reynolds, M. Kapanadze, S. Tabagari, L. |
Data pubblicazione: | 2016 | Rivista: | THE ASTROPHYSICAL JOURNAL | Numero: | 831 | Fascicolo: | 1 | Da pagina:: | 102 | Abstract: | We present the results of the Swift and NuSTAR observations of the nearby BL Lac object Mrk 421 during 2013 January-June. The source exhibited a strong long-term variability in the 0.3-10 keV and 3-79 keV bands with the maximum-to-minimum daily-binned flux ratios of 22 and 95, respectively, in about 3 months, mainly due to unprecedented strong X-ray outbursts by more than an order of magnitude in both bands within 2 weeks in 2013 April when the 0.3-10 keV count rate exceeded the level of 200 cts s<SUP>-1</SUP> for the first time, and Mrk 421 became one of the brightest sources in the X-ray sky. The source was also very active on intra-day timescales, and it showed flux doubling and halving timescales of 1.16-7.20 hr and 1.04-3.54 hr, respectively. On some occasions, the flux varied by 4%-23% within 300-840 s. During this period, the source also exhibited some of the most extreme X-ray spectral variability ever reported for BL Lacs—the location of the synchrotron spectral energy distribution peak shifted from a few eV to ∼10 keV, and the photon index at 1 keV and curvature parameter varied on timescales from a few weeks down to intervals shorter than 1 ks. MAGIC and First G-APD Cherenkov Telescope observations also revealed a very strong very high energy (VHE) flare during April 11-17. The UV and HE γ-ray flares were much weaker compared to their X-ray counterparts, and they generally showed significantly stronger correlation with each other than with the X-ray fluxes. | URI: | http://hdl.handle.net/20.500.12386/25876 | URL: | https://iopscience.iop.org/article/10.3847/0004-637X/831/1/102 | ISSN: | 0004-637X | DOI: | 10.3847/0004-637X/831/1/102 | Bibcode ADS: | 2016ApJ...831..102K | Fulltext: | open |
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