LONG-TERM MONITORING OF MRK 501 FOR ITS VERY HIGH ENERGYγ EMISSION AND A FLARE IN 2011 OCTOBER
- Autori: B. Bartoli; BERNARDINI, Paolo; X. J. Bi; C. Bleve; I. Bolognino; P. Branchini; A. Budano; A. K. Calabrese Melcarne; P. Camarri; Z. Cao; R. Cardarelli; S. Catalanotti; C. Cattaneo; S. Z. Chen; T. L. Chen; Y. Chen; P. Creti; S. W. Cui; B. Z. Dai; G. D’Al´ı Staiti; Danzengluobu; M. Dattoli; DE MITRI, Ivan; B. D’Ettorre Piazzoli; T. Di Girolamo; X. H. Ding; G. Di Sciascio; C. F. Feng; Zhaoyang Feng; Zhenyong Feng; F. Galeazzi; E. Giroletti; Q. B. Gou; Y. Q. Guo; H. H. He; Haibing Hu; Hongbo Hu; Q. Huang; M. Iacovacci; R. Iuppa; I. James; H. Y. Jia; Labaciren; H. J. Li; J. Y. Li; X. X. Li; G. Liguori; C. Liu; C. Q. Liu; J. Liu; M. Y. Liu; H. Lu; L. L. Ma; X. H. Ma; MANCARELLA, Giovanni; S. M. Mari; MARSELLA, GIOVANNI; MARTELLO, Daniele; S. Mastroianni; P. Montini; C. C. Ning; A. Pagliaro; PANAREO, Marco; B. Panico; PERRONE, Lorenzo; P. Pistilli; F. Ruggieri; P. Salvini; R. Santonico; P. R. Shen; X. D. Sheng; F. Shi; C. Stanescu; A. Surdo; Y. H. Tan; P. Vallania; S. Vernetto; C. Vigorito; B. Wang; H. Wang; C. Y. Wu; H. R. Wu; B. Xu; L. Xue; Q. Y. Yang; X. C. Yang; Z. G. Yao; A. F. Yuan; M. Zha; H. M. Zhang; Jilong Zhang; Jianli Zhang; L. Zhang; P. Zhang; X. Y. Zhang; Y. Zhang; J. Zhao; Zhaxiciren, Zhaxisangzhu; X. X. Zhou; F. R. Zhu; Q. Q. Zhu; G. Zizzi
- Anno di pubblicazione: 2012
- Tipologia: Articolo in rivista
- OA Link: http://hdl.handle.net/10447/466614
Abstract
As one of the brightest active blazars in both X-ray and very high energy γ-ray bands, Mrk 501, is very useful for physics associated with jets from active galactic nuclei. The ARGO-YBJ experiment has monitoredMrk 501 for γ-rays above 0.3 TeV since 2007 November. The largest flare since 2005 was observed from 2011 October and lasted until about 2012 April. In this paper, a detailed analysis of this event is reported. During the brightest γ-ray flaring episodes from 2011 October 17 to November 22, an excess of the event rate over 6σ is detected by ARGO-YBJ in the direction of Mrk 501, corresponding to an increase of the γ -ray flux above 1 TeV by a factor of 6.6 ± 2.2 from its steady emission. In particular, the γ -ray flux above 8 TeV is detected with a significance better than 4σ. Based on time-dependent synchrotron self-Compton (SSC) processes, the broadband energy spectrum is interpreted as the emission from an electron energy distribution parameterized with a single power-law function with an exponential cutoff at its high-energy end. The average spectral energy distribution for the steady emission is well described by this simple one-zone SSC model. However, the detection of γ -rays above 8 TeV during the flare challenges this model due to the hardness of the spectra. Correlations between X-rays and γ -rays are also investigated.