IDENTIFICATION OF THE TeV GAMMA-RAY SOURCE ARGO J2031+4157 WITH THE CYGNUS COCOON

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Abstract

The extended TeV gamma-ray source ARGO J2031+4157 (or MGRO J2031+41) is positionally consistent with the Cygnus Cocoon discovered by Fermi-LAT at GeV energies in the Cygnus superbubble. Reanalyzing the ARGO-YBJ data collected from 2007 November to 2013 January, the angular extension and energy spectrum of ARGO J2031+4157 are evaluated. After subtracting the contribution of the overlapping TeV sources, the ARGO-YBJ excess map is fitted with a two-dimensional Gaussian function in a square region of 10° × 10°, finding a source extension σ_ext = 1.8 ± 0.5 defrees. The observed differential energy spectrum is dN/dE = (2.5 ± 0.4) × 10^{–11} (E/1 TeV)^{–2.6 ± 0.3} photons cm–2 s–1 TeV–1, in the energy range 0.2-10 TeV. The angular extension is consistent with that of the Cygnus Cocoon as measured by Fermi-LAT and the spectrum also shows a good connection with the one measured in the 1-100 GeV energy range. These features suggest to identify ARGO J2031+4157 as the counterpart of the Cygnus Cocoon at TeV energies. The Cygnus Cocoon, located in the star-forming region of Cygnus X, is interpreted as a cocoon of freshly accelerated cosmic rays related to the Cygnus superbubble. The spectral similarity with supernova remnants (SNRs) indicates that the particle acceleration inside a superbubble is similar to that in an SNR. The spectral measurements from 1 GeV to 10 TeV allows for the first time to determine the possible spectrum slope of the underlying particle distribution. A hadronic model is adopted to explain the spectral energy distribution.

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  • B. Bartoli , P. Bernardini , X. J. Bi , P. Branchini , A. Budano , P. Camarri , Z. Cao , R. Cardarelli , S. Catalanotti , S. Z. Chen , T. L. Chen , P. Creti , S. W. Cui , B. Z. Dai , A. D'Amone , Danzengluobu , I. De Mitri , B. D'Ettorre Piazzoli , T. Di Girolamo , G. Di Sciascio , C. F. Feng , Zhaoyang Feng , Zhenyong Feng , Q. B. Gou , Y. Q. Guo , H. H. He , Haibing Hu , Hongbo Hu , M. Iacovacci , R. Iuppa , H. Y. Jia , Labaciren , H. J. Li , G. Liguori , C. Liu , J. Liu , M. Y. Liu , H. Lu , L. L. Ma , X. H. Ma , G. Mancarella , S. M. Mari , G. Marsella , D. Martello , S. Mastroianni , P. Montini , C. C. Ning , M. Panareo , L. Perrone , P. Pistilli , F. Ruggieri , P. Salvini , R. Santonico , P. R. Shen , X. D. Sheng , F. Shi , A. Surdo , Y. H. Tan , P. Vallania , S. Vernetto , C. Vigorito , H. Wang , C. Y. Wu , H. R. Wu , L. Xue , Q. Y. Yang , X. C. Yang , Z. G. Yao , A. F. Yuan , M. Zha , H. M. Zhang , L. Zhang , X. Y. Zhang , Y. Zhang , J. Zhao , Zhaxiciren , Zhaxisangzhu , X. X. Zhou , F. R. Zhu , Q. Q. Zhu , G. Zizzi

Titolo volume/Rivista

THE ASTROPHYSICAL JOURNAL

Anno di pubblicazione

2014

ISSN

0004-637X

ISBN

Non Disponibile

Numero di citazioni Wos

28

Ultimo Aggiornamento Citazioni

28/04/2018

Numero di citazioni Scopus

35

Ultimo Aggiornamento Citazioni

28/04/2018

Settori ERC

Non Disponibile

Codici ASJC

Non Disponibile