학술논문
Discovery of the linear energy-dependence of the spectral lag of X-ray bursts from SGR J1935+2154
Document Type
Working Paper
Author
Xiao, Shuo; Tuo, You-Li; Zhang, Shuang-Nan; Xiong, Shao-Lin; Lin, Lin; Zhang, Yan-Qiu; Wang, Yue; Xue, Wang-Chen; Cai, Ce; Gao, He; Li, Cheng-Kui; Li, Xiao-Bo; Zheng, Chao; Liu, Jia-Cong; Wang, Ping; Wang, Jin; Peng, Wen-Xi; Liu, Cong Zhan; Li, Xin-Qiao; Wen, Xiang-Yang; An, Zheng-Hua; Song, Li-Ming; Zheng, Shi-Jie; Zhang, Fan; Dong, Ai-Jun; Xie, Wei; Feng, Jian-Chao; Ma, Qing-Bo; Wang, De-Hua; Luo, Xi-Hong; Dang, Shi-Jun; Shang, Lun-Hua; Zhi, Qi-Jun; Li, Ti-Pei
Source
Subject
Language
Abstract
Spectral lag of the low-energy photons with respect to the high-energy ones is a common astrophysical phenomenon (such as Gamma-ray bursts and the Crab pulsar) and may serve as a key probe to the underlying radiation mechanism. However, spectral lag in keV range of the magnetar bursts has not been systematically studied yet. In this work, we perform a detailed spectral lag analysis with the Li-CCF method for SGR J1935+2154 bursts observed by {\it Insight}-HXMT, GECAM and Fermi/GBM from July 2014 to Jan 2022. We discover that the spectral lags of about 61\% (non-zero significance >1$\sigma$) bursts from SGR J1935+2154 are linearly dependent on the photon energy ($E$) with $t_{\rm lag}(E)=\alpha (E/{\rm keV})+C$, which may be explained by a linear change of the temperature of the blackbody-emitting plasma with time. The distribution of the slope ($\alpha$) approximately follows a Gaussian function with mean and standard deviation of 0.02 ms/keV (i.e. high-energy photons arrive earlier) and 0.02 ms/keV, respectively. We also find that the distribution can be well fitted with three Gaussians with mean values of $\sim$ -0.009, 0.013 and 0.039 ms/keV, which may correspond to different origins of the bursts. These spectral lag features may have important implications on the magnetar bursts.
Comment: accepted for publication in MNRAS
Comment: accepted for publication in MNRAS