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End-to-end study of the host galaxy and genealogy of the first binary neutron star merger


Binary neutron star mergers are one of the ultimate events of massive binary star evolution, and our understanding of their parent systems is still in its infancy. Upcoming gravitational wave detections, coupled with multi-wavelength follow-up observations, will allow us to study an increasing number of these events by characterizing their neighbouring stellar populations and searching for their progenitors. Stellar evolution simulations are essential to this work, but they are also based on numerous assumptions. Additionally, the models used to study the host galaxies differ from those used to characterize the progenitors and are typically based on single-star populations. Here we introduce a framework to perform an end-to-end analysis and deploy it to the first detected binary neutron star merger event, GW170817. With the Binary Population And Spectral Synthesis codes we are able to retrieve the physical properties of the host galaxy NGC 4993 as well as infer progenitor candidates. In our simulations, there is a >98% chance that GW170817 originated from a stellar population with metallicity Z = 0.010, born between 5 and 12.5 Gyr ago. By carefully weighing the stellar genealogies, we find that GW170817 most likely came from a binary system born with a 13–24 M primary and 10–12 M secondary that underwent 2 or 3 common envelope events over their lifetime.

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Fig. 1: SED fit and resulting star formation history of NGCC 4993.
Fig. 2: Summary characteristics of the progenitor candidates of GW170817 split by evolutionary channels.
Fig. 3: Kick-velocity distributions of GW170817 progenitor channels.

Data availability

The LIGO/Virgo posterior distributions are publicly available from The data resulting from the numerical simulations of supernova kicks used to perform this analysis (main text and Supplementary Information) are publicly available at

Code availability

BPASS v.2.2.1 can be found at or The hoki python package is available on GitHub ( and published in ref. 18. The data analysis codes used to perform this analysis (main text and Supplementary Information) are publicly available at


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H.F.S. and J.J.E. acknowledge the support of the Marsden Fund Council managed through Royal Society Te Aparangi. H.F.S. is thankful to L. Della Bruna, A. Adamo and C. Usher for private communications regarding the voronoi binning and ppxf algorithms. H.F.S. is grateful to S. Smartt for his comments on the final draft of the manuscript. E.R.S. acknowledges funding from the UK Science and Technology Facilities Council through Consolidated Grant ST/T000406/1. A.J.L. has received funding from the European Research Council under the European Union’s Horizon 2020 research and innovation programme (Grant agreement No. 725246).

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Authors and Affiliations



H.F.S. is the lead developer of hoki, created the pipelines to make BPASS SED templates, refactored the TUI codebase, performed the SED fitting and led the writing of this manuscript. J.J.E. conceived the project, is one of the lead developers of BPASS, wrote TUI, advised throughout the analysis and writing process and contributed text to Supplementary Information. E.R.S. is one of the lead developers of BPASS and commented on early and later drafts of the manuscript. J.L. provided relevant expertise on the SED fitting procedure and analysis of NGC 4993 as well as the data reduction used for this paper. A.F.M. advised on the handling of Multi Unit Spectroscopic Explorer data and SED fitting. A.J.L. led the initial acquisition of the data, provided text and advised on the manuscript.

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Correspondence to Heloise F. Stevance.

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Nature Astronomy thanks Matthias Kruckow and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Supplementary Figs. 1–14 and Sections 1–3.

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Stevance, H.F., Eldridge, J.J., Stanway, E.R. et al. End-to-end study of the host galaxy and genealogy of the first binary neutron star merger. Nat Astron 7, 444–450 (2023).

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