Swift Observations of Mrk 421 in Selected Epochs. IV. Physical Implications of X-Ray Flaring Activity and Features of Relativistic Magnetic Reconnection in 2018 April–2023 December
We present the spectral and timing results obtained during the intense observations of Mrk 421 by the Swift-based ultraviolet to X-ray instruments during 2018 April–2023 December. The source showed various strengths of X-ray flaring activity, exceeding a level of 3.5 × 10 ^−9 erg cm ^−2 s ^−1 during...
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2024-01-01
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| Online Access: | https://doi.org/10.3847/1538-4365/ad7d0c |
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| author | B. Kapanadze A. Gurchumelia M. Aller |
| author_facet | B. Kapanadze A. Gurchumelia M. Aller |
| author_sort | B. Kapanadze |
| collection | DOAJ |
| description | We present the spectral and timing results obtained during the intense observations of Mrk 421 by the Swift-based ultraviolet to X-ray instruments during 2018 April–2023 December. The source showed various strengths of X-ray flaring activity, exceeding a level of 3.5 × 10 ^−9 erg cm ^−2 s ^−1 during the strongest 0.3–10 keV flares. Our study identifies a number of intraday brightness variability, including 61 instances that occurred within 1 ks exposures that are consistent with the shock-in-jet scenario and accompanied by significant, fast spectral changes. The source exhibited extreme spectral properties with dominance of the log-parabolic distributions of photons with energy and the frequent occurrence of hard photon indices in the 0.3–10 keV and 0.3–300 GeV bands, with the peak of synchrotron spectral energy distribution E _p detected at the energies beyond 29 keV for the first time. The source showed very fast transitions of log-parabolic-to-power-law spectra, most plausibly caused by turbulence-driven relativistic magnetic reconnection. Our spectral results also demonstrate the importance of the first-order Fermi mechanism within the magnetic field of different confinement efficiencies, stochastic acceleration, transitions in the turbulence spectrum, and hadronic cascades. The X-ray, UV, and γ -ray fluxes showed a lognormal variability, which hints at the imprint of accretion disk instabilities on the blazar jet, as well as the possible presence of hadronic cascades. The UV and γ -ray variabilities demonstrated weak correlations with the X-ray flaring activity, which is not consistent with simple synchrotron self-Compton models and requires more complex particle acceleration and emission scenarios. |
| format | Article |
| id | doaj-art-ff3636f92bc04c8fbd9d976359f14718 |
| institution | OA Journals |
| issn | 0067-0049 |
| language | English |
| publishDate | 2024-01-01 |
| publisher | IOP Publishing |
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| series | The Astrophysical Journal Supplement Series |
| spelling | doaj-art-ff3636f92bc04c8fbd9d976359f147182025-08-20T02:14:07ZengIOP PublishingThe Astrophysical Journal Supplement Series0067-00492024-01-0127522310.3847/1538-4365/ad7d0cSwift Observations of Mrk 421 in Selected Epochs. IV. Physical Implications of X-Ray Flaring Activity and Features of Relativistic Magnetic Reconnection in 2018 April–2023 DecemberB. Kapanadze0https://orcid.org/0000-0002-7146-6751A. Gurchumelia1M. Aller2https://orcid.org/0000-0003-2483-2103Ilia State University , Colokashvili Av. 3/5, Tbilisi, 0162, Georgia; E. Kharadze National Astrophysical Observatory , Mt. Kanobili, Abastumani, 0803, Georgia; INAF , Osservatorio Astronomico di Brera, Via E. Bianchi 46, 23807 Merate, ItalyE. Kharadze National Astrophysical Observatory , Mt. Kanobili, Abastumani, 0803, Georgia; I. Javakhishvili State University , Chavchavadze Av. 3, Tbilisi 0128, GeorgiaAstronomy Department, University of Michigan , Ann Arbor, MI 48109-1107, USAWe present the spectral and timing results obtained during the intense observations of Mrk 421 by the Swift-based ultraviolet to X-ray instruments during 2018 April–2023 December. The source showed various strengths of X-ray flaring activity, exceeding a level of 3.5 × 10 ^−9 erg cm ^−2 s ^−1 during the strongest 0.3–10 keV flares. Our study identifies a number of intraday brightness variability, including 61 instances that occurred within 1 ks exposures that are consistent with the shock-in-jet scenario and accompanied by significant, fast spectral changes. The source exhibited extreme spectral properties with dominance of the log-parabolic distributions of photons with energy and the frequent occurrence of hard photon indices in the 0.3–10 keV and 0.3–300 GeV bands, with the peak of synchrotron spectral energy distribution E _p detected at the energies beyond 29 keV for the first time. The source showed very fast transitions of log-parabolic-to-power-law spectra, most plausibly caused by turbulence-driven relativistic magnetic reconnection. Our spectral results also demonstrate the importance of the first-order Fermi mechanism within the magnetic field of different confinement efficiencies, stochastic acceleration, transitions in the turbulence spectrum, and hadronic cascades. The X-ray, UV, and γ -ray fluxes showed a lognormal variability, which hints at the imprint of accretion disk instabilities on the blazar jet, as well as the possible presence of hadronic cascades. The UV and γ -ray variabilities demonstrated weak correlations with the X-ray flaring activity, which is not consistent with simple synchrotron self-Compton models and requires more complex particle acceleration and emission scenarios.https://doi.org/10.3847/1538-4365/ad7d0cBlazars |
| spellingShingle | B. Kapanadze A. Gurchumelia M. Aller Swift Observations of Mrk 421 in Selected Epochs. IV. Physical Implications of X-Ray Flaring Activity and Features of Relativistic Magnetic Reconnection in 2018 April–2023 December The Astrophysical Journal Supplement Series Blazars |
| title | Swift Observations of Mrk 421 in Selected Epochs. IV. Physical Implications of X-Ray Flaring Activity and Features of Relativistic Magnetic Reconnection in 2018 April–2023 December |
| title_full | Swift Observations of Mrk 421 in Selected Epochs. IV. Physical Implications of X-Ray Flaring Activity and Features of Relativistic Magnetic Reconnection in 2018 April–2023 December |
| title_fullStr | Swift Observations of Mrk 421 in Selected Epochs. IV. Physical Implications of X-Ray Flaring Activity and Features of Relativistic Magnetic Reconnection in 2018 April–2023 December |
| title_full_unstemmed | Swift Observations of Mrk 421 in Selected Epochs. IV. Physical Implications of X-Ray Flaring Activity and Features of Relativistic Magnetic Reconnection in 2018 April–2023 December |
| title_short | Swift Observations of Mrk 421 in Selected Epochs. IV. Physical Implications of X-Ray Flaring Activity and Features of Relativistic Magnetic Reconnection in 2018 April–2023 December |
| title_sort | swift observations of mrk 421 in selected epochs iv physical implications of x ray flaring activity and features of relativistic magnetic reconnection in 2018 april 2023 december |
| topic | Blazars |
| url | https://doi.org/10.3847/1538-4365/ad7d0c |
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