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Published September 2022 | public
Journal Article

An X-ray-quiet black hole born with a negligible kick in a massive binary within the Large Magellanic Cloud

Abstract

Stellar-mass black holes are the final remnants of stars born with more than 15 solar masses. Billions are expected to reside in the Local Group, yet only a few are known, mostly detected through X-rays emitted as they accrete material from a companion star. Here, we report on VFTS 243: a massive X-ray-faint binary in the Large Magellanic Cloud. With an orbital period of 10.4 d, it comprises an O-type star of 25 solar masses and an unseen companion of at least nine solar masses. Our spectral analysis excludes a non-degenerate companion at a 5σ confidence level. The minimum companion mass implies that it is a black hole. No other X-ray-quiet black hole is unambiguously known outside our Galaxy. The (near-)circular orbit and kinematics of VFTS 243 imply that the collapse of the progenitor into a black hole was associated with little or no ejected material or black-hole kick. Identifying such unique binaries substantially impacts the predicted rates of gravitational-wave detections and properties of core-collapse supernovae across the cosmos.

Additional Information

This research has received funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (T.S. and H.S., grant agreement 772225: MULTIPLES). T.S. acknowledges support from the European Union's Horizon 2020 programme under Marie Skłodowska-Curie grant agreement 101024605. This work is based on observations collected at the ESO under programme IDs 182.D-0222, 090.D-0323 and 092.D-0136. L.M. thanks the ESA and the Belgian Federal Science Policy Office (BELSPO) for their support in the framework of the PRODEX programme. P. Marchant acknowledges support from FWO junior postdoctoral fellowship 12ZY520N. We thank J. Hillier for making the CMFGEN code available. C.H. acknowledges support from the KU Leuven Research Council (grant C16/17/007: MAESTRO). P.A.C. acknowledges support from UK Science and Technology Facilities Council research grant ST/V000853/1. V.H.-B. acknowledges the support of the Natural Sciences and Engineering Research Council of Canada (NSERC) through grant RGPIN-2020-05990. M. Gieles acknowledges support from the Ministry of Science and Innovation through a Europa Excelencia grant (EUR2020-112157). The PoWR code, as well as the associated post-processing and visualization tool WRplot, has been developed under the guidance of W.-R. Hamann with substantial contributions from L. Koesterke, G. Gräfener, A. Sander, T.S. and other co-workers and students. This work has received funding from the ERC under the European Union's Horizon 2020 research and innovation programme (grant agreement 945806). It is also supported by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) under Germany's Excellence Strategy EXC 2181/1-390900948 (the Heidelberg STRUCTURES Excellence Cluster). S.T. acknowledges support from the Netherlands Research Council NWO (grants VENI 639.041.645, VIDI 203.061). A.H. and D.J.L. acknowledge support by the Spanish MCI through grant PGC-2018-0913741-B-C22 and the Severo Ochoa Programme through CEX2019-000920-S. J.M.A. acknowledges support from the Spanish Government Ministerio de Ciencia, Innovación y Universidades through grant PGC2018-095-049-B-C22. We thank I. Mayo and S. Pinilla for their work on the visualization of VFTS 243. We acknowledge the Cambridge Astronomical Survey Unit and ESO for the background image in Fig. 1. This research has made use of the SIMBAD database, operated at CDS, Strasbourg, France. Contributions. T.S, H.S., L.M. and M.F. developed the analysis methodology. T.S. identified the target, performed the disentangling and simulations, derived the radial velocities, analysed the spectrum with PoWR and wrote the manuscript. H.S. led the TMBM observing campaign, prepared the observations and, together with L.A.A., performed data reduction, variability and orbital analysis of the TMBM sample and contributed to the interpretation. L.M. analysed the spectrum with CMFGEN. K.E.-B. performed the light-curve analysis, investigated the spectra independently and produced mock simulations for blind testing. P.M. and N.L. contributed to the interpretation of the evolutionary status and X-ray properties of the system. C.H. analysed the spectrum with FASTWIND. M.F. performed an independent test with Fourier disentangling. K.S. contributed to the discussion of X-ray production. D.J.L. contributed to the assessment of the light ratios of hypothetical main-sequence stars and investigated the spectra independently. J.M.A. provided an independent measure of the stellar parameters and luminosity. P.M., A.P., F.R.N.S. and M.G. contributed to the computation of synchronization and circularization timescales. All other authors contributed to acquisition of the data and discussion of the results and commented on the manuscript. Data availability. The VFTS and TMBM spectra are available in the ESO archives (archive.eso.org/cms.html). The input files of our stellar evolution model (Supplementary Information) are available at https://zenodo.org/record/6514646. The OGLE light curve is available for download at https://cdsarc.u-strasbg.fr/ftp/vizier.submit/OGLE_VFTS243. Any other processed materials are available from the corresponding author upon reasonable request. Code availability. The fd3 tool used for Fourier disentangling is available online (http://sail.zpf.fer.hr/fdbinary/). The shift-and-add Python implementation used here is available from the corresponding author upon reasonable request. We refer the reader to the CMFGEN (http://kookaburra.phyast.pitt.edu/hillier/web/CMFGEN.htm), PoWR (www.astro.physik.uni-potsdam.de/PoWR), FASTWIND (fys.kuleuven.be/ster/research-projects/equation-folder/codes-folder/fastwind) and PHOEBE (http://phoebe-project.org/) webpages for access and availability policies. The authors declare no competing interests. Nature Astronomy thanks Sebastian Gomez and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

Additional details

Created:
August 22, 2023
Modified:
October 24, 2023