Frost, A. J. ; Sana, H. ; Mahy, L. ; Wade, G. ; Barron, J. ; Le Bouquin, J. -B. ; Mérand, A. ; Schneider, F. R. N. ; Shenar, T. ; Barbá, R. H. ; Bowman, D. M. ; Fabry, M. ; Farhang, A. ; Marchant, P. ; Morrell, N. I. ; Smoker, J. V.

published in Science, 384 issue 6692, pp. 214-217 (2024)

Abstract: Massive stars (those ≥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.

DOI: 10.1126/science.adg7700