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arXiv · 1911.11989

A wide star-black-hole binary system from radial-velocity measurements

Jifeng Liu·Haotong Zhang·Andrew W. Howard·Zhongrui Bai·Youjun Lu·Roberto Soria·Stephen Justham·Xiangdong Li·Zheng Zheng·Tinggui Wang·Krzysztof Belczynski·Jorge Casares·Wei Zhang·Hailong Yuan·Yiqiao Dong·Yajuan Lei·Howard Isaacson·Song Wang·Yu Bai·Yong Shao·Qing Gao·Yilun Wang·Zexi Niu·Kaiming Cui·Chuanjie Zheng·Xiaoyong Mu·Lan Zhang·Wei Wang·Alexander Heger·Zhaoxiang Qi·Shilong Liao·Mario Lattanzi·Wei-Min Gu·Junfeng Wang·Jianfeng Wu·Lijing Shao·Rongfeng Shen·Xiaofeng Wang·Joel Bregman·Rosanne Di Stefano·Qingzhong Liu·Zhanwen Han·Tianmeng Zhang·Huijuan Wang·Juanjuan Ren·Junbo Zhang·Jujia Zhang·Xiaoli Wang·Antonio Cabrera-Lavers·Romano Corradi·Rafael Rebolo·Yongheng Zhao·Gang Zhao·Yaoquan Chu·Xiangqun Cui
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Abstract

All stellar mass black holes have hitherto been identified by X-rays emitted by gas that is accreting onto the black hole from a companion star. These systems are all binaries with black holes below 30 M$_{\odot}$$^{1-4}$. Theory predicts, however, that X-ray emitting systems form a minority of the total population of star-black hole binaries$^{5,6}$. When the black hole is not accreting gas, it can be found through radial velocity measurements of the motion of the companion star. Here we report radial velocity measurements of a Galactic star, LB-1, which is a B-type star, taken over two years. We find that the motion of the B-star and an accompanying H$\alpha$ emission line require the presence of a dark companion with a mass of $68^{+11}_{-13}$ M$_{\odot}$, which can only be a black hole. The long orbital period of 78.9 days shows that this is a wide binary system. The gravitational wave experiments have detected similarly massive black holes$^{7,8}$, but forming such massive ones in a high-metallicity environment would be extremely challenging to current stellar evolution theories$^{9-11}$.

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Jifeng Liu, Haotong Zhang, Andrew W. Howard, Zhongrui Bai, Youjun Lu, Roberto Soria, Stephen Justham, Xiangdong Li, Zheng Zheng, Tinggui Wang, Krzysztof Belczynski, Jorge Casares, Wei Zhang, Hailong Yuan, Yiqiao Dong, Yajuan Lei, Howard Isaacson, Song Wang, Yu Bai, Yong Shao, Qing Gao, Yilun Wang, Zexi Niu, Kaiming Cui, Chuanjie Zheng, Xiaoyong Mu, Lan Zhang, Wei Wang, Alexander Heger, Zhaoxiang Qi, Shilong Liao, Mario Lattanzi, Wei-Min Gu, Junfeng Wang, Jianfeng Wu, Lijing Shao, Rongfeng Shen, Xiaofeng Wang, Joel Bregman, Rosanne Di Stefano, Qingzhong Liu, Zhanwen Han, Tianmeng Zhang, Huijuan Wang, Juanjuan Ren, Junbo Zhang, Jujia Zhang, Xiaoli Wang, Antonio Cabrera-Lavers, Romano Corradi, Rafael Rebolo, Yongheng Zhao, Gang Zhao, Yaoquan Chu, Xiangqun Cui. 2019-11-27. A wide star-black-hole binary system from radial-velocity measurements. https://doi.org/10.1038/s41586-019-1766-2

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