CRAB NEBULA: FIVE-YEAR OBSERVATION WITH ARGO-YBJ

作者：B. Bartoli, P. Bernardini, X. J. Bi, P. Branchini, A. Budano, P. Camarri, Z. Cao, R. Cardarelli, Sergio Catalanotti, S. Z. Chen, T. L. Chen, P. Creti, S. W. Cui, B. Z. Dai, A. D׳Amone, Danzengluobu Danzengluobu, I. De Mitri, Benedetto D’Ettorre Piazzoli, T. Di Girolamo, G. Di Sciascio, C. Feng, Zhaoyang Feng, Zhenyong Feng, Q. B. Gou, Yi-Qing Guo, H. H. He, Haibing Hu, Hongbo Hu, Michele Iacovacci, R. Iuppa, H. Y. Jia, Labaciren Labaciren, H. J. Li, Giorgia Liguori, Chunhong Liu, J. Liu, M. Y. Liu, Hong Laura Lu, L. L., Xinhua Ma, G. Mancarella, S. M. Mari, G. Marsella, Donald V. Martello, S. Mastroianni, P. Montini, C. C. Ning, M. Panareo, Lorenzo Perrone, P. Pistilli, F. Ruggieri, P. Salvini, R. Santonico, P. R. Shen, X. D. Sheng, F. Shi, Antonio Lo Surdo, Y. H. Tan, P. Vallania, S. Vernetto, Carlo Francesco Vigorito, H. Wang, C. Y. Wu, H. Wu, L. Xue, Q. Y. Yang, X. C. Yang, Z. G. Yao, A. F. Yuan, Min Zha, Hongwei Zhang, Li Zhang, X. Y. Zhang, Yi Zhang, J. Y. Zhao, Zhaxiciren Zhaxiciren, Zhaxisangzhu, X. X. Zhou, F. R. Zhu, Q. Q. Zhu, Giovanni Zizzi, E. Striani · 发表于：The Astrophysical Journal · 年份：2015 · DOI：10.1088/0004-637x/798/2/119 · 被引用次数：44 · 研究领域：Astrophysics and Cosmic Phenomena、Dark Matter and Cosmic Phenomena、Gamma-ray bursts and supernovae

The ARGO-YBJ air shower detector monitored the Crab Nebula gamma-ray emission from 2007 November to 2013 February. The integrated signal, consisting of ∼3.3 × 10 5 events, reached the statistical significance of 21.1 standard deviations. The obtained energy spectrum in the energy range 0.3–20 TeV can be described by a power law function dN / dE = I 0 ( E /2 TeV) −α , with a flux normalization I 0 = (5.2 ± 0.2) × 10 −12 photons cm −2 s −1 TeV −1 and α = 2.63 ± 0.05, corresponding to an integrated flux above 1 TeV of 1.97 × 10 −11 photons cm −2 s −1 . The systematic error is estimated to be less than 30% for the flux normalization and 0.06 for the spectral index. Assuming a power law spectrum with an exponential cutoff dN / dE = I 0 ( E /2 TeV) −α exp (− E / E cut ), the lower limit of the cutoff energy E cut is 12 TeV, at 90% confidence level. Our extended data set allows the study of the TeV emission over long timescales. Over five years, the light curve of the Crab Nebula in 200-day bins is compatible with a steady emission with a probability of 7.3 × 10 −2 . A correlated analysis with Fermi -LAT data over ∼4.5 yr using the light curves of the two experiments gives a Pearson correlation coefficient r = 0.56 ± 0.22. Concerning flux variations on timescales of days, a "blind" search for flares with a duration of 1–15 days gives no excess with a significance higher than four standard deviations. The average rate measured by ARGO-YBJ during the three most powerful flares detecte...