论文

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

发布时间:2021-05-17
 
  • Liu, Jifeng;
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  • Zhang, Haotong;
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  • Howard, Andrew W.;
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  • Bai, Zhongrui;
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  • Lu, Youjun;
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  • Soria, Roberto;
  • Justham, Stephen;
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  • Li, Xiangdong;
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  • Zheng, Zheng;
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  • Wang, Tinggui;
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  • Belczynski, Krzysztof;
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  • Casares, Jorge;
  • Zhang, Wei;
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  • Yuan, Hailong;
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  • Dong, Yiqiao;
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  • Lei, Yajuan;
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  • Isaacson, Howard;
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  • Wang, Song;
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  • Bai, Yu;
  • Shao, Yong
  • All stellar-mass black holes have hitherto been identified by X-rays emitted from gas that is accreting onto the black hole from a companion star. These systems are all binaries with a black-hole mass that is less than 30 times that of the Sun1-4. Theory predicts, however, that X-ray-emitting systems form a minority of the total population of star-black-hole binaries5,6. 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 taken over two years of the Galactic B-type star, LB-1. We find that the motion of the B star and an accompanying Hα emission line require the presence of a dark companion with a mass of 68-13+11 solar masses, which can only be a black hole. The long orbital period of 78.9 days shows that this is a wide binary system. Gravitational-wave experiments have detected black holes of similar mass, but the formation of such massive ones in a high-metallicity environment would be extremely challenging within current stellar evolution theories.

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