Detection of Very High-energy Gamma-Ray Emission from the Radio Galaxy M87 with LHAASO

Z. Cao, F Aharonian, Axikegu, Yuting Bai, Yiwang Bao, D. Bastieri, Xiao-Jun Bi, Y.J Bi, W Bian, A.V Bukevich, Qian Cao, W.Y Cao, Zhe Cao, J. Chang, J. F. Chang, A.M Chen, E.S Chen, Hua-Xing Chen, Liang Chen, Lin Chen, Long Chen, M.J Chen, M.L Chen, Qin Chen, Shengyong Chen, Shaw H. Chen, S. Z. Chen, T. L. Chen, Yiqun Chen, Na Cheng, Y.D Cheng, Micheline C. Chu, Maxwell Cui, S. W. Cui, X.H Cui, Y. D. Cui, B. Z. Dai, H. L. Dai, Z. G. Dai, Danzengluobu Danzengluobu, X.Q Dong, K. K. Duan, Junhui Fan, Yi-Zhong Fan, Jingzhong Fang, J. Fang, Kun Fang, C.F Feng, H Feng, Lei Feng, Shuo Feng, X.T Feng, Y. X. Feng, Yulong Feng, S. Gabici(Université Paris Cité), Bo Gao, Chuyue Gao, Qing Gao, Wei Gao, Wei Gao, M.M Ge, T.T Ge, Li‐Sheng Geng, Gwenael Giacinti, G. Gong, Q. B. Gou, M. H. Gu, Fulai Guo, J. Guo, Xu Guo, Y. Q. Guo, Yong Guo, Y.A Han, O. A. Hannuksela, M Hasan, H.H He, H. N. He, Jiangbiao He, Yan He, Y. K. Hor, Bowen Hou, Changbo Hou, Xianglin Hou, H.B Hu, Q. Hu, S. C. Hu, Chen Huang, D.H Huang, T.Q Huang, Weidong Huang, X. T. Huang, X.Y Huang, Yiming Huang, Yanyi Huang, X. L. Ji, H.Y Jia, Ke Jia, Hongbing Jiang, K. Jiang, Xiaojun Jiang, Z.J Jiang, Mingzhou Jin, M. M. Kang, I. Karpikov, D. Khangulyan, D. Kuleshov, K. Kurinov, Bing Li, C.M Li, Cheng Li, Cong Li, D. Li, Li Fei, Haibo Li, H.C Li, Jian Li, Jie Li, Kuo Li, Shaoquan Li, W.L Li, W.L Li, X.R. Li, Xin Li, Yuze Li, Zhe Li, Zhuo Li, E.W Liang, Yun-Feng Liang, S.J Lin, B. Liu, Cuiping Liu, Di Liu, D. Liu, Haibo Liu, H.D Liu, Jian Liu, J.L Liu, M. Liu, Rui Liu, S.M Liu, W Liu, Yinong Liu, Yu‐Rong Liu, Qian Luo, Yangping Luo, H.K Lv, B.Q Ma, L.L. Ma, Xinhua Ma, J.R Mao, Z. Min, W. Mitthumsiri, Haowei Mu, Y. C. Nan, A. Neronov(Université Paris Cité), K.C.Y Ng, L.J Ou, P. Pattarakijwanich, Z. Y. Pei, J.C Qi, Ming Qi, Bing-Qiang Qiao, J. J. Qin, Ahmed Raza, D. Ruffolo, A. Sáiz, Mansoor Saeed, D. Semikoz(Université Paris Cité), Lu Shao, O. Shchegolev, X. D. Sheng, Fengchun Shu, H. C. Song, Yu.V Stenkin, V. I. Stepanov, Yang Su, D.X Sun, Q. N. Sun, X.N Sun, Z. B. Sun, J. Takata, P. H. T. Tam, Q.W Tang, Ryan W. Tang, Z.B Tang, W.W. Tian, L.H Wan, C. Wang, C.B Wang, G.W Wang, H.G Wang, H.H Wang, Jincheng Wang, Kai Wang, Kai Wang, L.P Wang, L.Y Wang, Ping Wang, Renheng Wang, Wei Wang, X.G Wang, X. Y. Wang, Yuhua Wang, Y.D Wang, Y.J Wang, Z.H Wang, Z.X Wang, Zhen Wang, Zheng Wang, D. M. Wei, Jinjia Wei, Y. Wei, T. Wen, Chuan‐Yu Wu, H. R. Wu, Qi Wu, Shizhe Wu, X.F Wu, Yabin Wu, Shichuan Xi, Jing Xia, G. M. Xiang, Dong Xiao, G. Q. Xiao, Y. Xin, Yalan Xing, D.R Xiong, Zhen Xiong, D.L Xu, R.F Xu, Rui Xu, Weiwei Xu, W. Xu, D.H Yan, Jing‐Zhi Yan, Ting Yan, Chul Woo Yang, C. Y. Yang, Fang Yang, F.F Yang, Lili Yang, Mo Yang, Ruizhi Yang, W.X Yang, Y. Yao, Z. G. Yao, Lina Yin, N Yin, X. H. You, Z. Y. You, Y.H. Yu, Qiping Yuan, Hui Yue, Houdun Zeng, T. X. Zeng, W Zeng, M. Zha, Bin‐Bin Zhang, F Zhang, Haowen Zhang, H.M Zhang, Hengyun Zhang, J.L Zhang, Lu Zhang, Peng Zhang, P.P Zhang, Rui Zhang, Shengbai Zhang, S.R Zhang, S.S Zhang, Xian Zhang, X.P Zhang, Y.F Zhang, Yi Zhang, Yong Zhang, Bing Zhao, J. Zhao, Long Zhao, Lei Zhao, Shujie Zhao, Xinsheng Zhao, Fa‐Kun Zheng, W.J Zhong, Bo Zhou, Hongyan Zhou, J. N. Zhou, Mi Zhou, Ping Zhou, Ruijie Zhou, Xiaoxin Zhou, Xiaoxin Zhou, Baohua Zhu, C. G. Zhu, F.R Zhu, Hongming Zhu, K. J. Zhu, Yuan-Chuan Zou, X. Zuo
The Astrophysical Journal Letters
November 1, 2024
10.3847/2041-8213/ad8921
Cited by 11Open Access
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Abstract

Abstract The nearby radio galaxy M87 is a very high-energy (VHE) gamma-ray emitter established by observations with ground-based gamma-ray detectors. Here we report the long-term monitoring of M87 from 2021 to 2024 with the Large High Altitude Air Shower Observatory (LHAASO). M87 has been detected by LHAASO with a statistical significance ∼ 9 σ . The observed energy spectrum extends to 20 TeV, with a possible hardening at ∼20 TeV and then a clear softening at higher energies. Assuming that the intrinsic spectrum is described by a single power law up to 20 TeV, a tight upper bound on the extragalactic background light intensity is obtained. A strong VHE flare lasting 8 days, with a rise time of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow> <mml:mi>τ</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>r</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>rise</mml:mi> </mml:mrow> </mml:msubsup> <mml:mo>=</mml:mo> <mml:mn>1.05</mml:mn> <mml:mo>±</mml:mo> <mml:mn>0.49</mml:mn> </mml:math> days and decay time of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow> <mml:mi>τ</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>d</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>decay</mml:mi> </mml:mrow> </mml:msubsup> <mml:mo>=</mml:mo> <mml:mn>2.17</mml:mn> <mml:mo>±</mml:mo> <mml:mn>0.58</mml:mn> </mml:math> days, was found in early 2022. A possible GeV flare is seen also in Fermi Large Area Telescope data during the VHE flare period. The variability time as short as 1 day seen in the LHAASO data suggests a compact emission region with a size of ∼3 × 10 15 δ cm ( δ being the Doppler factor of the emitting region), corresponding to a few Schwarzschild radii of the central supermassive black hole in M87. The continuous monitoring of the source reveals a duty cycle of ∼1% for VHE flares with a flux above 10 −11 erg cm −2 s −1 .

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