Massive stars (those larger than 8 solar masses at formation) have radiative envelopes that cannot sustain a dynamo, the mechanism that produces magnetic fields in lower-mass stars. Despite this, approximately 7\% of massive stars have observed magnetic fields, the origin of which is debated. We used multi-epoch interferometric and spectroscopic observations to characterize HD 148937, a binary system of two massive stars. We found that only one star is magnetic and that it appears younger than its companion. The system properties and a surrounding bipolar nebula can be reproduced with a model in which two stars merged (in a previous triple system) to produce the magnetic massive star. Our results provide observational evidence that magnetic fields form in at least some massive stars through stellar mergers.
@article{arxiv.2404.10167,
title = {A magnetic massive star has experienced a stellar merger},
author = {A. J. Frost and H. Sana and L. Mahy and G. Wade and J. Barron and J. -B. Le Bouquin and A. Mérand and F. R. N. Schneider and T. Shenar and R. H. Barbá and D. M. Bowman and M. Fabry and A. Farhang and P. Marchant and N. I. Morrell and J. V. Smoker},
journal= {arXiv preprint arXiv:2404.10167},
year = {2024}
}
Comments
Full paper with supplementary materials. 59 pages, 18 figures