MULTIWAVELENGTH STUDY OF QUIESCENT STATES OF MRK 421 WITH UNPRECEDENTED HARD X-RAY COVERAGE PROVIDED BY NuSTAR IN 2013

Please use this identifier to cite or link to this item: https://ir.lib.ncu.edu.tw/handle/987654321/101887

Title:	MULTIWAVELENGTH STUDY OF QUIESCENT STATES OF MRK 421 WITH UNPRECEDENTED HARD X-RAY COVERAGE PROVIDED BY NuSTAR IN 2013
Authors:	陳文屏;Richards, J.L;Nelson, T;Moody, J.W;Falcone, A;Longo, F;Colombo, E;Lelas, D;Feng, Q;Idec, W;Ibryamov, S;Williams, D.A;Font, L;Sun, S;Hahn, A;Todd, N.W;Hayashida, M;Sadun, A.C;Kubo, H;Moretti, E;Acosta-Pulido, J.A;Biland, A;Larionova, E.G;Readhead, A.C.R;Semkov, E;Blanch, O;Connolly, M.P;Nishijima, K;Biasuzzi, B;Garrido Terrats, D;Treves, A;Reinthal, R;Cui, W;Lin, H.C;Hailey, C;Maneva, G;Fernández-Barral, A;Hanabata, Y;Kieda, D;Carosi, A;Guberman, D;Teshima, M;Godinović, N;Fidalgo, D;Temnikov, P;Glawion (Eisenacher), D;Jorstad, S.G;Bangale, P;Fleischhack, H;Poutanen, J;Hughes, G;Sobczynska, D;Bachev, R;Chatterjee, A;Strigachev, A;Damljanovic, G;Kertzman, M;López, M;Palacio, J;Karamanavis, V;Mao, P.H;Delgado Mendez, C;Tammi, J;Carmona, E;Galindo, D;Sievers, A;Madsen, K.K;De Angelis, A;Krennrich, F;Barnes, J;Fruck, C;Lähteenmäki, A;Boggs, S.E;Zitzer, B;Archambault, S;Gaug, M;Hornstrup, A;Nieto, D;Verguilov, V;Noda, K;Snidaric, I;Kopatskaya, E.N;Kitaguchi, T;Strzys, M;González Muñoz, A;Mannheim, K;Martínez, M;Bugaev, V;Richards, G.T;Sitarek, J;Madejski, G;Giommi, P;Prandini, E;Rhode, W;Paoletti, R;Kurtanidze, S.O;Latev, G;Troitsky, I.S;Jordan, B;Shore, S.N;Alexander, D.M
Contributors:	理學院天文研究所
Keywords:	Astrophysics and Astronomy;Astrophysics,ASTRO, GRQC;BL Lacertae objects;BL Lacertae objects: individual (Markarian 421);Broadband;Correlation analysis;Fluxes;galaxies: active;gamma rays: general;Mathematical models;radiation mechanisms: nonthermal;Spectral energy distribution;Synchrotrons;X-rays;X-rays: galaxies
Date:	2016-03-10
Issue Date:	2026-04-21 14:50:13 (UTC+8)
Publisher:	IOP Publishing Ltd.;United States: The American Astronomical Society
Abstract:	摘要： We present coordinated multiwavelength observations of the bright, nearby BL Lac object Mrk 421 taken in 2013 January-March, involving GASP-WEBT, Swift, NuSTAR, Fermi-LAT, MAGIC, VERITAS, and other collaborations and instruments, providing data from radio to very-high-energy (VHE) gamma-ray bands. NuSTAR yielded previously unattainable sensitivity in the 3-79 keV range, revealing that the spectrum softens when the source is dimmer until the X-ray spectral shape saturates into a steep power law with a photon index of approximately 3, with no evidence for an exponential cutoff or additional hard components up to about 80 keV. For the first time, we observed both the synchrotron and the inverse-Compton peaks of the spectral energy distribution (SED) simultaneously shifted to frequencies below the typical quiescent state by an order of magnitude. The fractional variability as a function of photon energy shows a double-bump structure which relates to the two bumps of the broadband SED. In each bump, the variability increases with energy which, in the framework of the synchrotron self-Compton model, implies that the electrons with higher energies are more variable. The measured multi-band variability, the significant X-ray-to-VHE correlation down to some of the lowest fluxes ever observed in both bands, the lack of correlation between optical/UV and X-ray flux, the low degree of polarization and its significant (random) variations, the short estimated electron cooling time, and the significantly longer variability timescale observed in the NuSTAR light curves point toward in-situ electron acceleration, and suggest that there are multiple compact regions contributing to the broadband emission of Mrk 421 during low-activity states. We present coordinated multiwavelength observations of the bright, nearby BL Lac object Mrk 421 taken in 2013 January-March, involving GASP-WEBT, Swift, NuSTAR, Fermi-LAT, MAGIC, VERITAS, and other collaborations and instruments, providing data from radio to very-high-energy (VHE) gamma-ray bands. NuSTAR yielded previously unattainable sensitivity in the 3-79 keV range, revealing that the spectrum softens when the source is dimmer until the X-ray spectral shape saturates into a steep power law with a photon index of approximately 3, with no evidence for an exponential cutoff or additional hard components up to about 80 keV. For the first time, we observed both the synchrotron and the inverse-Compton peaks of the spectral energy distribution (SED) simultaneously shifted to frequencies below the typical quiescent state by an order of magnitude. The fractional variability as a function of photon energy shows a double-bump structure which relates to the two bumps of the broadband SED. In each bump, the variability increases with energy which, in the framework of the synchrotron self-Compton model, implies that the electrons with higher energies are more variable. The measured multi-band variability, the significant X-ray-to-VHE correlation down to some of the lowest fluxes ever observed in both bands, the lack of correlation between optical/UV and X-ray flux, the low degree of polarization and its significant (random) variations, the short estimated electron cooling time, and the significantly longer variability timescale observed in the NuSTAR light curves point toward in-situ electron acceleration, and suggest that there are multiple compact regions contributing to the broadband emission of Mrk 421 during low-activity states. 其他題名： APJ 其他題名： Astrophys. J 出版者： United States: The American Astronomical Society 出版日期： 2016-03-10 出處： The Astrophysical journal, 2016-03, Vol.819 (2), p.156 資源來源： Institute of Physics Journals 版權： 2016. The American Astronomical Society. All rights reserved. 識別號： ISSN: 0004-637X 識別號： ISSN: 1538-4357 識別號： EISSN: 1538-4357 識別號： DOI: 10.3847/0004-637X/819/2/156
Appears in Collections:	[Graduate Institute of Astronomy] journal & Dissertation

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