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Reply to: On the signature of a 70-solar-mass black hole in LB-1

Nature volume 580, pages E16–E17 (2020)Cite this article

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The Original Article was published on 29 April 2020

replying to: M. Abdul-Masih et al. Nature https://doi.org/10.1038/s41586-020-2217-9 (2020)

We reported1 a wide black-hole binary LB-1, discovered through a designated radial-velocity-monitoring campaign of a large sample of stars. Our estimate of the mass of the black hole of approximately 70M⊙ rests on the following arguments, some of which have been questioned in the accompanying Comment by Abdul-Masih et al.2 and by others3,4,5,6: (1) the Hα emission line comes from a disk around the black hole, seen moderately face-on as evidenced by its wine-bottle shape; (2) the barycentre motion of the Hα emission line wings traces the motion of the black hole and the absorption lines trace the motion of the donor star; and (3) the donor star has an effective temperature of Teff = 18,100 ± 820 K, the surface gravity is logg = 3.43 ± 0.15, and it has an evolutionary mass of \({8.2}_{-1.2}^{+0.9}\)M⊙. Here we re-examine those arguments, in light of more recent spectroscopic observations and further analysis. We show that the data still favour a very high mass of 23M⊙–65M⊙ (with a most probable donor mass range of 5M⊙–8M⊙); other lower-mass solutions are possible but less likely. Distinguishing definitively between solutions will require further Gaia astrometry data.

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References

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Acknowledgements

We thank S. Justham, W. Hamann, S. Wang and many others for discussions. This work was supported by the National Science Foundation of China (NSFC) under grant numbers 11988101/11933004 (J.L.), 11690024 (Y.L.) and 11603035 (S.W.). This work was also supported by the National Key Research and Development Program of China (NKRDPC) under grant numbers 2019YFA0405504/2016YFA0400804 (J.L.) and 2016YFA0400704 (Y.L). J.L. acknowledges support by the Tencent Xplore Prize.

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Authors and Affiliations

  1. Key Laboratory of Optical Astronomy, National Astronomical Observatories, Chinese Academy of Sciences, Beijing, China

    Jifeng Liu, Haotong Zhang, Youjun Lu, Song Wang & Hailong Yuan

  2. School of Astronomy and Space Sciences, University of Chinese Academy of Sciences, Beijing, China

    Jifeng Liu, Roberto Soria & Youjun Lu

  3. WHU-NAOC Joint Center for Astronomy, Wuhan University, Wuhan, China

    Jifeng Liu

  4. Sydney Institute for Astronomy, School of Physics, The University of Sydney, Sydney, New South Wales, Australia

    Roberto Soria

  5. Department of Physics and Astronomy, University of Utah, Salt Lake City, UT, USA

    Zheng Zheng

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  1. Jifeng Liu
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The present author list includes only those authors of the original paper who have now contributed substantially to the writing of this Reply. J.L. and R.S. drafted the manuscript, and all other authors contributed substantially to the discussion and revision.

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Correspondence to Jifeng Liu.

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Liu, J., Soria, R., Zheng, Z. et al. Reply to: On the signature of a 70-solar-mass black hole in LB-1. Nature 580, E16–E17 (2020). https://doi.org/10.1038/s41586-020-2217-9

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