Confirming the spin parameter of the black hole in Cygnus X-1 using the Insight-HXMT

• Published in: Journal of high energy astrophysics Vol. 27; pp. 53 - 63
• Main Authors: Zhao, Xue-Shan, Dong, Yan-Ting, Feng, Ye, Jia, Nan, Li, Yu-Feng, Liao, Zhen-Xuan, Liu, Ji-Ren, Zheng, Xue-Ying, Zhang, Shuang-Nan, Song, Li-Ming, Zhang, Shu, Cai, Ce, Cao, Xue-Lei, Chen, Li, Chen, Tian-Xiang, Chen, Yi-Bao, Chen, Yu-Peng, Cui, Wei, Deng, Jing-Kang, Dong, Yong-Wei, Du, Yuan-Yuan, Fu, Min-Xue, Gao, Guan-Hua, Gao, He, Gao, Min, Ge, Ming-Yu, Gu, Yu-Dong, Guan, Ju, Guo, Cheng-Cheng, Han, Da-Wei, Huang, Yue, Huo, Jia, Jia, Shu-Mei, Jiang, Wei-Chun, Jin, Jing, Kong, Ling-Da, Li, Bing, Li, Cheng-Kui, Li, Gang, Li, Mao-Shun, Li, Ti-Pei, Li, Xian, Li, Yan-Guo, Li, Zheng-Wei, Liang, Xiao-Hua, Liao, Jin-Yuan, Liu, Bai-Sheng, Liu, Guo-Qing, Liu, Hong-Wei, Liu, Xiao-Jing, Liu, Yi-Nong, Lu, Bo, Lu, Fang-Jun, Lu, Xue-Feng, Luo, Qi, Luo, Tao, Ma, Xiang, Meng, Bin, Nang, Yi, Sai, Na, Song, Xin-Ying, Sun, Liang, Tan, Ying, Tao, Lian, Tuo, You-Li, Wang, Guo-Feng, Wang, Juan, Wang, Wen-Shuai, Wang, Yu-Sa, Wen, Xiang-Yang, Wu, Bai-Yang, Wu, Bo-Bing, Xiao, Guang-Cheng, Xiao, Shuo, Yang, Sheng, Yang, Yi-Rong, Yi, Qi-Bin, Yin, Qian-Qing, You, Yuan, Zhang, Ai-Mei, Zhang, Cheng-Mo, Zhang, Fan, Zhang, Juan, Zhang, Tong, Zhang, Wan-Chang, Zhang, Wei, Zhang, Wen-Zhao, Zhang, Yi, Zhang, Yi-Fei, Zhang, Yong-Jie, Zhang, Yue, Zhang, Zhi, Zhang, Zi-Liang, Zhao, Hai-Sheng, Zhao, Xiao-Fan, Zheng, Shi-Jie, Zhou, Jian-Feng, Zhu, Yu-Xuan, Yue-Zhu, Zhuang, Ren-Lin
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.08.2020
• Subjects: Black hole physics; Insight-HXMT; X-rays: binaries; X-rays: individual (Cygnus X-1); X-rays: binaries; Insight-HXMT; Black hole physics; X-rays: individual (Cygnus X-1)
• ISSN: 2214-4048
• DOI: 10.1016/j.jheap.2020.03.001

Recently, the system parameters of Cygnus X-1, i.e., the black hole mass M, the orbital inclination i and the source distance D, have been updated. As the input constraints of the continuum-fitting method, it is necessary to refine the spin with these new parameters. The Hard X-ray Modulation Telescope (HXMT, also named Insight) was successfully launched on June 15th, 2017 in China. In this work, we analyzed spectra obtained by the Insight-HXMT during 2017-2018 and re-estimated the spin via the continuum-fitting method. We first re-estimated the spin using old parameters and found the dimensionless spin parameter to be a⁎>0.934 (3σ), which is consistent with previous measurements both from the continuum-fitting and iron-line fitting methods (Gou et al. 2011, Gou et al. 2014; Fabian et al. 2012, Walton et al. 2016, Tomsick et al. 2018). Then, when the new parameters were applied, we obtained an increased spin: a⁎>0.967 (3σ), which is also consistent with the recent measurement (Zhao et al. 2020, submitted to ApJ) and also confirms an extreme Kerr black hole lying in this system.