LONG-TERM MONITORING OF THE TeV EMISSION FROM Mrk 421 WITH THE ARGO-YBJ EXPERIMENT
- Autori: Bartoli, B; Bernardini, P; Bi, XJ; Bleve, C; Bolognino, I; Branchini, P; Budano, A; Calabrese Melcarne, AK; Camarri, P; Cao, Z; Cappa, A; Cardarelli, R; Catalanotti, S; Cattaneo, C; Celio, P; Chen, SZ; Chen, TL; Chen, Y; Creti, P; Cui SW; Dai, BZ; D'Alà Staiti, G; Danzengluobu; Dattoli, M; De Mitri, I; D'Ettorre Piazzoli, B; Di Girolamo, T; Ding, XH; Di Sciascio, G; Feng CF; Feng, XYa; Feng, ZYo; Galeazzi, F; Galeotti, P; Giroletti, E; Gou, QB; Guo, YQ; He, HH; Hu, HBi; Hu, HBo; Huang, Q; Iacovacci, M; Iuppa, R; James, I; Jia, HY; Labaciren; Li, HJ; Li, JY; Li, XX; Liguori, G; Liu, C; Liu, CQ; Liu, J; Liu, MY; Lu, H; Ma, XH; Mancarella, G; Mari, SM; Marsella, G; Martello, D; Mastroianni, S; Montini, P; Ning, CC; Pagliaro, A; Panareo, M; Panico, B; Perrone, L; Pistilli, P; Qu, XB; Rossi, E; Ruggieri, F; Salvini, P; Santonico, R; Shen, PR; Sheng, XD; Shi, F; Stanescu, C; Surdo, A; Tan, YH; Vallania, P; Vernetto, S; Vigorito, C; Wang, B; Wang, H; Wu, CY; Wu, HR; Xu, B; Xue, L; Yan, YX; Yang, QY; Yang, XC; Yao, ZG; Yuan, AF; Zha, M; Zhang, HM;Zhang, JLo; Zhang,JLi; Zhang,L; Zhang, P; Zhang, XY; Zhang, Y; Zhaxiciren; Zhaxisangzhu; Zhou, XX; Zhu, FR; Zhu, QQ; Zizzi, G
- Anno di pubblicazione: 2011
- Tipologia: Articolo in rivista (Articolo in rivista)
- Parole Chiave: Gamma-rays, Markarian 421, BL Lacertae, Resistive Plate Chambers
- OA Link: http://hdl.handle.net/10447/55524
Abstract
ARGO-YBJ is an air shower detector array with a fully covered layer of resistive plate chambers. It is operated with a high duty cycle and a large field of view. It continuously monitors the northern sky at energies above 0.3 TeV. In this paper, we report a long-term monitoring of Mrk 421 over the period from 2007 November to 2010 February. This source was observed by the satellite-borne experiments Rossi X-ray Timing Explorer and Swift in the X-ray band. Mrk 421 was especially active in the first half of 2008. Many flares are observed in both X-ray and γ-ray bands simultaneously. The γ-ray flux observed by ARGO-YBJ has a clear correlation with the X-ray flux. No lag between the X-ray and γ-ray photons longer than 1 day is found. The evolution of the spectral energy distribution is investigated by measuring spectral indices at four different flux levels. Hardening of the spectra is observed in both X-ray and γ-ray bands. The γ-ray flux increases quadratically with the simultaneously measured X-ray flux. All these observational results strongly favor the synchrotron self-Compton process as the underlying radiative mechanism.