OBSERVATION OF TeV GAMMA RAYS FROM THE UNIDENTIFIED SOURCE HESS J1841–055 WITH THE ARGO-YBJ EXPERIMENT

Bartoli, B.; Bernardini, Paolo; X. J., Bi; Bolognino, I.; Branchini, P.; Budano, A.; Calabrese Melcarne, A. K.; Camarri, P.; Cao, Z.; Cardarelli, R.; Catalanotti, S.; Cattaneo, C.; Chen, S. Z.; Chen, T. L.; Chen, Y.; Creti, P.; Cui, S. W.; Dai, B. Z.; D'Alí Staiti, G.; D'Amone, Antonio; Danzengluobu,; DE MITRI, Ivan; D'Ettorre Piazzoli, B.; Di Girolamo, T.; Ding, X. H.; Di Sciascio, G.; Feng, C. F.; Feng, Zhaoyang; Feng, Zhenyong; Galeazzi, F.; Giroletti, E.; Gou, Q. B.; Guo, Y. Q.; H. H., He; Haibing, Hu; Hongbo, Hu; Huang, Q.; Iacovacci, M.; Iuppa, R.; James, I.; Jia, H. Y.; Labaciren,; H. J., Li; J. Y., Li; X. X., Li; Liguori, G.; Liu, C.; Liu, C. Q.; Liu, J.; Liu, M. Y.; Lu, H.; L. L., Ma; X. H., Ma; Mancarella, Giovanni; Mari, S. M.; Marsella, Giovanni; Martello, Daniele; Mastroianni, S.; Montini, P.; Ning, C. C.; Pagliaro, A.; Panareo, Marco; Panico, B.; Perrone, Lorenzo; Pistilli, P.; Ruggieri, F.; Salvini, P.; Santonico, R.; Sbano, S. N.; Shen, P. R.; Sheng, X. D.; Shi, F.; Surdo, A.; Tan, Y. H.; Vallania, P.; Vernetto, S.; Vigorito, C.; Wang, B.; Wang, H.; C. Y., Wu; H. R., Wu; Xu, B.; Xue, L.; Yang, Q. Y.; Yang, X. C.; Yao, Z. G.; Yuan, A. F.; Zha, M.; Zhang, H. M.; Zhang, Jilong; Zhang, Jianli; Zhang, L.; Zhang, P.; 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/767/2/99

We report the observation of a very high energy gamma-ray source whose position is coincident with HESS J1841−055. This source has been observed for 4.5 years by the ARGO-YBJ experiment from 2007 November to 2012 July. Its emission is detected with a statistical significance of 5.3 standard deviations. Parameterizing the source shape with a two-dimensional Gaussian function, we estimate an extension σ = (0.40+0.32−0.22)°, which is consistent with the HESS measurement. The observed energy spectrum is dN/dE=(9.0±1.6)×10**(−13) (E/5 TeV)**(− 2.32±0.23) photons cm−2 s−1 TeV−1, in the energy range 0.9–50 TeV. The integral gamma-ray flux above 1 TeV is 1.3±0.4 Crab, which is 3.2±1.0 times the flux derived by HESS. The differences in the flux determination between HESS and ARGO-YBJ and possible counterparts at other wavelengths are discussed.