Abstract

Contributed Talk - Splinter MassiveStars

Thursday, 10 September 2026, 17:05   (MW-1050)

Internal Fields and Where to Find Them: Theoretical Predictions from Binary-Stripped Helium Stars

Giovanni Stimamiglio, Ylva Götberg, Jing-Ze Ma, Selma E. de Mink
Max Planck Institute for Astrophysics

Magnetic fields play a fundamental role in the evolution of massive stars by transporting angular momentum and influencing the rotation of both the star and the compact remnant it ultimately produces. Rapidly rotating, highly magnetized stellar cores are thought to collapse into magnetars and power energetic transients. Yet only a small fraction of massive stars host detectable surface magnetic fields, while internal fields remain largely inaccessible. Binary stripping provides a unique opportunity to probe these hidden fields. When a massive star loses its envelope through interaction with a companion, its internal magnetic field can become exposed and potentially detectable. We present predictions for the magnetic field strengths of binary-stripped helium stars under three hypotheses for the origin of magnetic fields in massive stars: (I) fossil fields, (II) convective core dynamos, and (III) rotational shear dynamos. Our results are based on a grid of one-dimensional MESA models spanning different stripped-star masses (hypotheses I and II) and rotation rates (hypothesis III). The convective core hypothesis (assuming equipartition) consistently predicts fields of strengths up to a few 10^5 G for all masses, while both the fossil field and rotational shear hypotheses yield upper estimates roughly an order of magnitude lower. These values are consistent with predictions from asteroseismology of red giant cores. Our predictions can be tested against magnetic field measurements of stripped stars and stellar remnants, helping to distinguish between competing scenarios for the origin of magnetism in massive stars. They also provide a theoretical benchmark for the recently discovered population of binary-stripped helium stars and future observational surveys.