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  • Discovery of the Ultrahigh-...
    Bai, L. X.; Bi, X. J.; Cai, J. T.; Chang, J.; Chang, J. F.; Chen, E. S.; Chen, J.; Chen, S. Z.; Chen, T. L.; Chen, X. L.; Cheng, N.; Cui, Y. D.; Dai, Z. G.; Dan-Zeng-Luo-Bu, Dan-Zeng; Volpe, D. della; Fan, J. H.; Fang, K.; Feng, Y. L.; Gao, B.; Gao, C. D.; Guo, Y. Y.; Han, Y. A.; He, S. L.; He, X. B.; He, Y.; Heller, M.; Hor, Y. K.; Hou, C.; Huang, X. T.; Ji, X. L.; Levochkin, K.; Li, F.; Li, H. B.; Li, H. C.; Li, H. Y.; Li, X. R.; Li, Xin; Li, Y.; Liang, Y. F.; Liu, B.; Liu, H.; Liu, J.; Liu, J. L.; Liu, Z. X.; Lv, H. K.; Ma, B. Q.; Ma, L. L.; Ma, X. H.; Mitthumsiri, W.; Pang, B. Y.; Pei, Z. Y.; Qiao, B. Q.; Ruffolo, D.; Rulev, V.; Sáiz, A.; Sheng, X. D.; Sun, Q. N.; Sun, Z. B.; Tam, P. H. T.; Tang, Z. B.; Wang, B. D.; Wang, C.; Wang, H.; Wang, L. P.; Wang, W.; Wang, X. Y.; Wang, Y. J.; Wang, Z. H.; Wang, Z. X.; Wang, Zhen; Wei, J. J.; Wei, Y. J.; Wen, T.; Wu, C. Y.; Wu, H. R.; Wu, X. F.; Xiao, D. X.; Xiao, G.; Xin, G. G.; Xin, Y. L.; Yan, J. Z.; Yang, J. Y.; Yang, S. B.; Ye, Y. M.; Yin, N.; Yu, Y. H.; Zha, M.; Zhai, X. X.; Zhang, B. B.; Zhang, P. F.; Zhang, P. P.; Zhang, R.; Zhang, Y. L.; Zhang, Yi; Zhang, Yong; Zhou, J. N.; Zhou, X. X.; Zhu, F. R.; Zhu, H.; Zuo, X.

    Astrophysical journal. Letters, 10/2021, Letnik: 919, Številka: 2
    Journal Article

    Abstract We report the discovery of an ultrahigh-energy (UHE) gamma-ray source, LHAASO J2108+5157, by analyzing the LHAASO-KM2A data of 308.33 live days. A significant excess of gamma ray–induced showers is observed in both energy bands of 25−100 and >100 TeV with 9.5 σ and 8.5 σ , respectively. This source is not significantly favored as an extended source with an angular extension smaller than the point-spread function of KM2A. The measured energy spectrum from 20 to 200 TeV can be approximately described by a power-law function with an index of −2.83 ± 0.18 stat . A harder spectrum is demanded at lower energies considering the flux upper limit set by Fermi-LAT observations. The position of the gamma-ray emission is correlated with a giant molecular cloud, which favors a hadronic origin. No obvious counterparts have been found, and deeper multiwavelength observations will help to cast new light on this intriguing UHE source.