A high fraction of close massive binary stars at low metallicity
Abstract
At high metallicity, a majority of massive stars have at least one close stellar companion. The evolution of such binaries is subject to strong interaction processes, heavily impacting the characteristics of their life-ending supernova and compact remnants. For the low-metallicity environments of high-redshift galaxies constraints on the multiplicity properties of massive stars over the separation range leading to binary interaction are crucially missing. Here we show that the presence of massive stars in close binaries is ubiquitous, even at low metallicity. Using the Very Large Telescope, we obtained multi-epoch radial velocity measurements of a representative sample of 139 massive O-type stars across the Small Magellanic Cloud, which has a metal content of about one fifth of the solar value. We find that 45% of them show radial velocity variations which demonstrate that they are members of close binary systems, and predominantly have orbital periods shorter than one year. Correcting for observational biases indicates that at least 70[+11:-6]% of the O stars in our sample are in close binaries, and that at least 68[+7:-8]% of all O stars interact with a companion star during their lifetime. We found no evidence supporting a statistically significant trend of the multiplicity properties with metallicity. Our results indicate that multiplicity and binary interactions govern the evolution of massive stars and determine their cosmic feedback and explosive fates.
Keywords
Cite
@article{arxiv.2509.12488,
title = {A high fraction of close massive binary stars at low metallicity},
author = {H. Sana and T. Shenar and J. Bodensteiner and N. Britavskiy and N. Langer and D. J. Lennon and L. Mahy and I. Mandel and S. E. de Mink and L. R. Patrick and J. I. Villasenor and M. Dirickx and M. Abdul-Masih and L. A. Almeida and F. Backs and S. R. Berlanas and M. Bernini-Peron and D. M. Bowman and V. A. Bronner and P. A. Crowther and K. Deshmukh and C. J. Evans and M. Fabry and M. Gieles and A. Gilkis and G. Gonzalez-Tora and G. Grafener and Y. Gotberg and C. Hawcroft and V. Henault-Brunet and A. Herrero and G. Holgado and R. G. Izzard and A. de Koter and S. Janssens and C. Johnston and J. Josiek and S. Justham and V. M. Kalari and J. Klencki and J. Kubat and B. Kubatova and R. R. Lefever and J. Th. van Loon and B. Ludwig and J. Mackey and J. Maiz Apellaniz and G. Maravelias and P. Marchant and T. Mazeh and A. Menon and M. Moe and F. Najarro and L. M. Oskinova and R. Ovadia and D. Pauli and M. Pawlak and V. Ramachandran and M. Renzo and D. F. Rocha and A. A. C. Sander and F. R. N. Schneider and A. Schootemeijer and E. C. Schosser and C. Schurmann and K. Sen and S. Shahaf and S. Simon-Diaz and L. A. C. van Son and M. Stoop and S. Toonen and F. Tramper and R. Valli and A. Vigna-Gomez and J. S. Vink and C. Wang and R. Willcox},
journal= {arXiv preprint arXiv:2509.12488},
year = {2025}
}
Comments
32 pages, 12 figures