Crab Nebula: Five-year Observation with ARGO-YBJ
Journal
Date Issued
2015
Author(s)
Bartoli, B.
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Bernardini, P.
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Bi, X. J.
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Branchini, P.
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Budano, A.
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Camarri, P.
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Cao, Z.
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Cardarelli, R.
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Catalanotti, S.
•
Chen, S. Z.
•
Chen, T. L.
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Creti, P.
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Cui, S. W.
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Dai, B. Z.
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D'Amone, A.
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Danzengluobu
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De Mitri, I.
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D'Ettorre Piazzoli, B.
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Di Girolamo, T.
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Di Sciascio, G.
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Feng, C. F.
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Feng, Zhaoyang
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Feng, Zhenyong
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Gou, Q. B.
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Guo, Y. Q.
•
He, H. H.
•
Hu, Haibing
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Hu, Hongbo
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Iacovacci, M.
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Iuppa, R.
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Jia, H. Y.
•
Labaciren
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Li, H. J.
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Liguori, G.
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Liu, C.
•
•
Liu, M. Y.
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Lu, H.
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Ma, L. L.
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Ma, X. H.
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Mancarella, G.
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Mari, S. M.
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Marsella, G.
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Martello, D.
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Mastroianni, S.
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Montini, P.
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Ning, C. C.
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Panareo, M.
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Perrone, L.
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Pistilli, P.
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Ruggieri, F.
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Salvini, P.
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Santonico, R.
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Shen, P. R.
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Sheng, X. D.
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Shi, F.
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Surdo, A.
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Tan, Y. H.
•
•
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Vigorito, C.
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Wang, H.
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Wu, C. Y.
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Wu, H. R.
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Xue, L.
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Yang, Q. Y.
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Yang, X. C.
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Yao, Z. G.
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Yuan, A. F.
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Zha, M.
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Zhang, H. M.
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Zhang, L.
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Zhang, X. Y.
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Zhang, Y.
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Zhao, J.
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Zhaxiciren
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Zhaxisangzhu
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Zhou, X. X.
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Zhu, F. R.
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Zhu, Q. Q.
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Zizzi, G.
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ARGO-YBJ Collaboration
•
Striani, E.
Description
This work is supported in China by NSFC (No. 10120130794), the Chinese Ministry of Science and Technology, the Chinese Academy of Science, the Key Laboratory of Particle Astrophysics, CAS, and in Italy by the Istituto Nazionale di Fisica Nucleare (INFN). We also acknowledge the essential support of W. Y. Chen, G. Yang, X. F. Yuan, C. Y. Zhao, R. Assiro, B. Biondo, S. Bricola, F. Budano, A. Corvaglia, B. D'Aquino, R. Esposito, A. Innocente, A. Mangano, E. Pastori, C. Pinto, E. Reali, F. Taurino, and A. Zerbini in the installation, debugging, and maintenance of the detector.
Abstract
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 × 105 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 detected by Fermi-LAT is 205 ± 91 photons day-1, consistent with the average value of 137 ± 10 day-1.
Volume
798
Issue
2
Start page
119
Issn Identifier
0004-637X
Ads BibCode
2015ApJ...798..119B
Rights
open.access
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