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The data that support the plots within this paper and other findings of this study are available from the corresponding author upon reasonable request.
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Acknowledgements
We acknowledge support from the Fonds Wetenschappelijk Onderzoek (FWO, Research Foundation Flanders) under project IDs G0F8H6N, G0B3818N, 12ZY520N, G0H5416N and GST-D6267-I002519N, and from the Onderzoeksraad (Research Council), KU Leuven under project IDs C16/17/007, C16/18/005 and C14/17/082. This project received funding from the European Research Council under the European Union’s Horizon 2020 research and innovation programme (grant agreement numbers 772225 MULTIPLES and 670519 MAMSIE).
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This paper is based on an original idea by M.A.-M. J.B. prepared the observations. L.V. was the observer. H.V.W. and G.R. performed the HERMES data reduction. J.B. and L.M. performed the atmospheric analysis. M.A.-M., K.D., G.B. and T.S. studied the impact of the mixed profile on the radial-velocity measurements. D.M.B., E.B., M.F., L.M., T.S., A.T. and H.S. contributed to various aspects of the data analysis. All authors contributed to the discussion and interpretation of the results and commented on the written draft of the paper.
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Extended data figures and tables
Extended Data Fig. 1 Stellar atmosphere fitting to the LB-1 optical spectrum.
a, b, Top, best atmosphere model adjusted using the Grid Search in Stellar Parameters (GSSP) fitting suite (red) overlaid on the observed HERMES spectrum (black); and bottom, residuals of the fit. a and b each show a different small portion of the spectrum around the diagnostic lines of interest.
Extended Data Fig. 2 Chi-squared distributions of the atmosphere fitting.
a–d, Chi-squared maps of the GSSP atmosphere fitting projected on the one-dimensional parameter space for effective temperature (a), surface gravity (b), projected rotational velocity (c) and metallicity (d). The black data points are models, the blue solid and black dotted lines show linear and cubic interpolations through the best-fit grid points, respectively, and the horizontal red line corresponds to the adopted 1σ confidence threshold.
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Supplementary Information
This file contains Supplementary Methods and Discussion, Supplementary Figures 1–4 and Supplementary References.
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Abdul-Masih, M., Banyard, G., Bodensteiner, J. et al. On the signature of a 70-solar-mass black hole in LB-1. Nature 580, E11–E15 (2020). https://doi.org/10.1038/s41586-020-2216-x
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DOI: https://doi.org/10.1038/s41586-020-2216-x
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