4.5 Years of Multi-wavelength Observations of MRK 421 During the ARGO-YBJ and FERMI Common Operation Time

Journal
THE ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES
Date Issued
2016
Author(s)
Bartoli, B.
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Bernardini, P.
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Bi, X. J.
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Cao, Z.
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Catalanotti, S.
•
Chen, S. Z.
•
Chen, T. L.
•
Cui, S. W.
•
Dai, B. Z.
•
D'Amone, A.
•
Danzengluobu
•
De Mitri, I.
•
D'Ettorre Piazzoli, B.
•
Di Girolamo, T.
•
Di Sciascio, G.
•
Feng, C. F.
•
Feng, Zhaoyang
•
Feng, Zhenyong
•
Gou, Q. B.
•
Guo, Y. Q.
•
He, H. H.
•
Hu, Haibing
•
Hu, Hongbo
•
Iacovacci, M.
•
Iuppa, R.
•
Jia, H. Y.
•
Labaciren
•
Li, H. J.
•
Liu, C.
•
•
Liu, M. Y.
•
Lu, H.
•
Ma, L. L.
•
Ma, X. H.
•
Mancarella, G.
•
Mari, S. M.
•
Marsella, G.
•
Mastroianni, S.
•
Montini, P.
•
Ning, C. C.
•
Perrone, L.
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Pistilli, P.
•
Salvini, P.
•
Santonico, R.
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Shen, P. R.
•
Sheng, X. D.
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Shi, F.
•
Surdo, A.
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Tan, Y. H.
•
•
•
Vigorito, C.
•
Wang, H.
•
Wu, C. Y.
•
Wu, H. R.
•
Xue, L.
•
Yang, Q. Y.
•
Yang, X. C.
•
Yao, Z. G.
•
Yuan, A. F.
•
Zha, M.
•
Zhang, H. M.
•
Zhang, L.
•
Zhang, X. Y.
•
Zhang, Y.
•
Zhao, J.
•
Zhaxiciren
•
Zhaxisangzhu
•
Zhou, X. X.
•
Zhu, F. R.
•
Zhu, Q. Q.
•
ARGO-YBJ Collaboration
DOI
10.3847/0067-0049/222/1/6
Abstract
We report on the extensive multi-wavelength observations of the blazar Markarian 421 (Mrk 421) covering radio to γ-rays, during the 4.5 year period of ARGO-YBJ and Fermi common operation time, from 2008 August to 2013 February. These long-term observations, extending over an energy range of 18 orders of magnitude, provide a unique chance to study the variable emission of Mrk 421. In particular, due to the ARGO-YBJ and Fermi data, the entire energy range from 100 MeV to 10 TeV is covered without any gap. In the observation period, Mrk 421 showed both low- and high-activity states at all wavebands. The correlations among flux variations in different wavebands were analyzed. The X-ray flux is clearly correlated with the TeV γ-ray flux, while the GeV γ-rays only show a partial correlation with the TeV γ-rays. Radio and UV fluxes seem to be weakly or not correlated with the X-ray and γ-ray fluxes. Seven large flares, including five X-ray flares and two GeV γ-ray flares with variable durations (3-58 days), and one X-ray outburst phase were identified and used to investigate the variation of the spectral energy distribution with respect to a relative quiescent phase. During the outburst phase and the seven flaring episodes, the peak energy in X-rays is observed to increase from sub-keV to a few keV. The TeV γ-ray flux increases up to 0.9-7.2 times the flux of the Crab Nebula. The behavior of GeV γ-rays is found to vary depending on the flare, a feature that leads us to classify flares into three groups according to the GeV flux variation. Finally, the one-zone synchrotron self-Compton model was adopted to describe the emission spectra. Two out of three groups can be satisfactorily described using injected electrons with a power-law spectral index around 2.2, as expected from relativistic diffuse shock acceleration, whereas the remaining group requires a harder injected spectrum. The underlying physical mechanisms responsible for different groups may be related to the acceleration process or to the environment properties.
Volume
222
Issue
1
Start page
6
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