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

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

doi:10.1088/0004-637X/790/2/152

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 deg × 10 deg, finding a source extension σ_ext= (1.8 ± 0.5) deg. The observed differential energy spectrum is dN/dE = (2.5 ± 0.4) × 10−11(E/1TeV)^(−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.

IDENTIFICATION OF THE TeV GAMMA-RAY SOURCE ARGO J2031+4157 WITH THE CYGNUS COCOON / B., Bartoli; P., Bernardini; X. J., Bi; P., Branchini; A., Budano; P., Camarri; Z., Cao; R., Cardarelli; Catalanotti, Sergio; 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; DI GIROLAMO, Tristano; G., Di Sciascio; C. F., Feng; Zhaoyang, Feng; Zhenyong, Feng; Q. B., Gou; Y. Q., Guo; H. H., He; Haibing, Hu; Hongbo, Hu; Iacovacci, Michele; 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. - In: THE ASTROPHYSICAL JOURNAL. - ISSN 0004-637X. - 790:(2014), p. 152. [10.1088/0004-637X/790/2/152]