Data: 14.04.2026

Piotr Kołaczek-Szymański (OAUW,PL)

In flagrante delicto: observing a massive magnetic star contracting after the merger

Streszczenie:
Unlike stars similar to the Sun, massive main-sequence stars lack a convective envelope that could generate a global magnetic field. Yet, about 7% of these stars display strong dipolar magnetic fields, and the origin of this magnetism remains an open question. One possible explanation is that this is a consequence of the merger of two stars. Theoretical models of stellar mergers on the main sequence predict that after the stars coalesce, the resulting object should contract, possibly spinning up the merger product. However, until now, this relatively short evolutionary phase has never been directly observed. We believe we found the first observational example of such an object. Our target star also has a companion in a relatively close orbit, suggesting that the merger occurred within an initially hierarchical triple system. These findings provide a rare observational evidence supporting the recent hypothesis that magnetic fields in massive stars originate from stellar mergers.