Investigation of the correlation patterns and the Compton dominance variability of Mrk 421 in 2017
We present a detailed characterisation and theoretical interpretation of the broadband emission of the paradigmatic TeV blazar Mrk 421, with a special focus on the multi-band flux correlations. The dataset has been collected through an extensive multi-wavelength campaign organised between 2016 Decem...
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| Main Authors: | , , , |
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| Corporate Authors: | , |
| Format: | Article (Journal) |
| Language: | English |
| Published: |
29 November 2021
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| In: |
Astronomy and astrophysics
Year: 2021, Volume: 655 |
| ISSN: | 1432-0746 |
| DOI: | 10.1051/0004-6361/202141004 |
| Online Access: | Verlag, lizenzpflichtig, Volltext: https://doi.org/10.1051/0004-6361/202141004 Verlag, lizenzpflichtig, Volltext: https://www.aanda.org/articles/aa/abs/2021/11/aa41004-21/aa41004-21.html 
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| Author Notes: | MAGIC Collaboration: V.A. Acciari [und viele weitere]; FACT Collaboration: D. Baack [und viele weitere]; Other groups and collaborations: F. D’Ammando, S.O. Kurtanidze, O.M. Kurtanidze, M.G. Nikolashvili [und viele weitere] |
| Summary: | We present a detailed characterisation and theoretical interpretation of the broadband emission of the paradigmatic TeV blazar Mrk 421, with a special focus on the multi-band flux correlations. The dataset has been collected through an extensive multi-wavelength campaign organised between 2016 December and 2017 June. The instruments involved are MAGIC, FACT, Fermi-LAT, Swift, GASP-WEBT, OVRO, Medicina, and Metsähovi. Additionally, four deep exposures (several hours long) with simultaneous MAGIC and NuSTAR observations allowed a precise measurement of the falling segments of the two spectral components.<i>Results.<i/> The very-high-energy (VHE; E >100 GeV) gamma rays and X-rays are positively correlated at zero time lag, but the strength and characteristics of the correlation change substantially across the various energy bands probed. The VHE versus X-ray fluxes follow different patterns, partly due to substantial changes in the Compton dominance for a few days without a simultaneous increase in the X-ray flux (i.e., orphan gamma-ray activity). Studying the broadband spectral energy distribution (SED) during the days including <i>NuSTAR<i/> observations, we show that these changes can be explained within a one-zone leptonic model with a blob that increases its size over time. The peak frequency of the synchrotron bump varies by two orders of magnitude throughout the campaign. Our multi-band correlation study also hints at an anti-correlation between UV-optical and X-ray at a significance higher than 3σ. A VHE flare observed on MJD 57788 (2017 February 4) shows gamma-ray variability on multi-hour timescales, with a factor ten increase in the TeV flux but only a moderate increase in the keV flux. The related broadband SED is better described by a two-zone leptonic scenario rather than by a one-zone scenario. We find that the flare can be produced by the appearance of a compact second blob populated by high energetic electrons spanning a narrow range of Lorentz factors, from to . |
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| Item Description: | Gesehen am 11.08.2022 |
| Physical Description: | Online Resource |
| ISSN: | 1432-0746 |
| DOI: | 10.1051/0004-6361/202141004 |