Observation of GRB 221009A early afterglow in X/$γ$-ray energy band
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arXiv
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| Natura: | Preprint |
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2023
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| _version_ | 1866914645652013056 |
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| author | Zheng, Chao Zhang, Yan-Qiu Xiong, Shao-Lin Li, Cheng-Kui Gao, He Xue, Wang-Chen Liu, Jia-Cong Wang, Chen-Wei Tan, Wen-Jun Peng, Wen-Xi An, Zheng-Hua Cai, Ce Ge, Ming-Yu Guo, Dong-Ya Huang, Yue Li, Bing Li, Ti-Pei Li, Xiao-Bo Li, Xin-Qiao Li, Xu-Fang Liao, Jin-Yuan Liu, Cong-Zhan Lu, Fang-Jun Ma, Xiang Qiao, Rui Song, Li-Ming Wang, Jin Wang, Ping Wang, Xi-Lu Wang, Yue Wen, Xiang-Yang Xiao, Shuo Xu, Yan-Bing Xu, Yu-Peng Yao, Zhi-Guo Yi, Qi-Bing Yi, Shu-Xu You, Yuan Zhang, Fan Zhang, Jin-Peng Zhang, Peng Zhang, Shu Zhang, Shuang-Nan Zhang, Yan-Ting Zhang, Zhen Zhao, Xiao-Yun Zhao, Yi Zheng, Shi-Jie |
| author_facet | Zheng, Chao Zhang, Yan-Qiu Xiong, Shao-Lin Li, Cheng-Kui Gao, He Xue, Wang-Chen Liu, Jia-Cong Wang, Chen-Wei Tan, Wen-Jun Peng, Wen-Xi An, Zheng-Hua Cai, Ce Ge, Ming-Yu Guo, Dong-Ya Huang, Yue Li, Bing Li, Ti-Pei Li, Xiao-Bo Li, Xin-Qiao Li, Xu-Fang Liao, Jin-Yuan Liu, Cong-Zhan Lu, Fang-Jun Ma, Xiang Qiao, Rui Song, Li-Ming Wang, Jin Wang, Ping Wang, Xi-Lu Wang, Yue Wen, Xiang-Yang Xiao, Shuo Xu, Yan-Bing Xu, Yu-Peng Yao, Zhi-Guo Yi, Qi-Bing Yi, Shu-Xu You, Yuan Zhang, Fan Zhang, Jin-Peng Zhang, Peng Zhang, Shu Zhang, Shuang-Nan Zhang, Yan-Ting Zhang, Zhen Zhao, Xiao-Yun Zhao, Yi Zheng, Shi-Jie |
| contents | The early afterglow of a Gamma-ray burst (GRB) can provide critical information on the jet and progenitor of the GRB. The extreme brightness of GRB 221009A allows us to probe its early afterglow in unprecedented detail. In this letter, we report comprehensive observation results of the early afterglow of GRB 221009A (from $T_0$+660 s to $T_0$+1860 s, where $T_0$ is the \textit{Insight}-HXMT/HE trigger time) in X/$γ$-ray energy band (from 20 keV to 20 MeV) by \textit{Insight}-HXMT/HE, GECAM-C and \textit{Fermi}/GBM. We find that the spectrum of the early afterglow in 20 keV-20 MeV could be well described by a cutoff power-law with an extra power-law which dominates the low and high energy bands respectively. The cutoff power-law $E_{\rm peak}$ is $\sim$ 30 keV and the power-law photon index is $\sim$ 1.8 throughout the early afterglow phase. By fitting the light curves in different energy bands, we find that a significant achromatic break (from keV to TeV) is required at $T_0$ + 1246$^{+27}_{-26}$ s (i.e. 1021 s since the afterglow starting time $T_{\rm AG}$=$T_0$+225 s), providing compelling evidence of a jet break. Interestingly, both the pre-break and post-break decay slopes vary with energy, and these two slopes become closer in the lower energy band, making the break less identifiable. Intriguingly, the spectrum of the early afterglow experienced a slight hardening before the break and a softening after the break. These results provide new insights into the understanding of this remarkable GRB. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2310_10522 |
| institution | arXiv |
| publishDate | 2023 |
| record_format | arxiv |
| spellingShingle | Observation of GRB 221009A early afterglow in X/$γ$-ray energy band Zheng, Chao Zhang, Yan-Qiu Xiong, Shao-Lin Li, Cheng-Kui Gao, He Xue, Wang-Chen Liu, Jia-Cong Wang, Chen-Wei Tan, Wen-Jun Peng, Wen-Xi An, Zheng-Hua Cai, Ce Ge, Ming-Yu Guo, Dong-Ya Huang, Yue Li, Bing Li, Ti-Pei Li, Xiao-Bo Li, Xin-Qiao Li, Xu-Fang Liao, Jin-Yuan Liu, Cong-Zhan Lu, Fang-Jun Ma, Xiang Qiao, Rui Song, Li-Ming Wang, Jin Wang, Ping Wang, Xi-Lu Wang, Yue Wen, Xiang-Yang Xiao, Shuo Xu, Yan-Bing Xu, Yu-Peng Yao, Zhi-Guo Yi, Qi-Bing Yi, Shu-Xu You, Yuan Zhang, Fan Zhang, Jin-Peng Zhang, Peng Zhang, Shu Zhang, Shuang-Nan Zhang, Yan-Ting Zhang, Zhen Zhao, Xiao-Yun Zhao, Yi Zheng, Shi-Jie High Energy Astrophysical Phenomena The early afterglow of a Gamma-ray burst (GRB) can provide critical information on the jet and progenitor of the GRB. The extreme brightness of GRB 221009A allows us to probe its early afterglow in unprecedented detail. In this letter, we report comprehensive observation results of the early afterglow of GRB 221009A (from $T_0$+660 s to $T_0$+1860 s, where $T_0$ is the \textit{Insight}-HXMT/HE trigger time) in X/$γ$-ray energy band (from 20 keV to 20 MeV) by \textit{Insight}-HXMT/HE, GECAM-C and \textit{Fermi}/GBM. We find that the spectrum of the early afterglow in 20 keV-20 MeV could be well described by a cutoff power-law with an extra power-law which dominates the low and high energy bands respectively. The cutoff power-law $E_{\rm peak}$ is $\sim$ 30 keV and the power-law photon index is $\sim$ 1.8 throughout the early afterglow phase. By fitting the light curves in different energy bands, we find that a significant achromatic break (from keV to TeV) is required at $T_0$ + 1246$^{+27}_{-26}$ s (i.e. 1021 s since the afterglow starting time $T_{\rm AG}$=$T_0$+225 s), providing compelling evidence of a jet break. Interestingly, both the pre-break and post-break decay slopes vary with energy, and these two slopes become closer in the lower energy band, making the break less identifiable. Intriguingly, the spectrum of the early afterglow experienced a slight hardening before the break and a softening after the break. These results provide new insights into the understanding of this remarkable GRB. |
| title | Observation of GRB 221009A early afterglow in X/$γ$-ray energy band |
| topic | High Energy Astrophysical Phenomena |
| url | https://arxiv.org/abs/2310.10522 |