Observation of GRB 221009A early afterglow in X/$γ$-ray energy band

• DOI: 10.48550/arxiv.2310.10522
• Publication Date: 2023-01-01
• Authors: Chao Zheng; Yanqiu Zhang; S. L. Xiong; Cheng-Kui Li; H. Gao; W. C. Xue; Jia-Cong Liu; Chen‐Wei Wang; Wenjun Tan; Wen-Xi Peng; Zhenghua An; Ce Cai; Mingyu Ge; D. Y. Guo; Y. Huang; Bing Li; Ti-Pei Li; Xiao‐Bo Li; Xin-Qiao Li; Xufang Li; J. Y. Liao; Congzhan Liu; F. J. Lu; Xiang Ma; Rui Qiao; L. M. Song; Jin Wang; Ping Wang; Xilu Wang; Yue Wang; Xiang-Yang Wen; Shuo Xiao; Yanbing Xu; Y. P. Xu; Z. G. Yao; Qi-Bing Yi; Shu-Xu Yi; Y. You; Fan Zhang; Jinpeng Zhang; Peng Zhang; Shuang‐Nan Zhang; Shuang‐Nan Zhang; Yanting Zhang; Zhen Zhang; Xiaoyun Zhao; Y. Zhao; S. J. Zheng
• Keywords: High Energy Astrophysical Phenomena (astro-ph.HE); FOS: Physical sciences

The early afterglow of a Gamma-ray burst (GRB) can provide critical information on the jet and progenitor GRB. extreme brightness GRB 221009A allows us to probe its in unprecedented detail. In this letter, we report comprehensive observation results (from $T_0$+660 s $T_0$+1860 s, where $T_0$ is \textit{Insight}-HXMT/HE trigger time) X/$\gamma$-ray energy band 20 keV MeV) by \textit{Insight}-HXMT/HE, GECAM-C \textit{Fermi}/GBM. We find that spectrum keV-20 MeV could be well described cutoff power-law with an extra which dominates low high bands respectively. $E_{\rm peak}$ $\sim$ 30 photon index 1.8 throughout phase. By fitting light curves different bands, significant achromatic break TeV) required at + 1246$^{+27}_{-26}$ (i.e. 1021 since starting time $T_{\rm AG}$=$T_0$+225 s), providing compelling evidence break. Interestingly, both pre-break post-break decay slopes vary energy, these two become closer lower band, making less identifiable. Intriguingly, experienced slight hardening before softening after These new insights into understanding remarkable