Post-merger rotational evolution of magnetised single hot subdwarfs results in slow rotation due to magnetic braking
Abstract
Single hot subdwarfs are believed to form through mergers of helium-core white dwarfs, which can lead to large-scale magnetic fields generated during the merger, and may be observable at the surface once they evolve into the stable core-helium burning phase. As a post-merger product, the orbital angular momentum of the binary system that forms it, could lead to a rapidly rotating hot subdwarf. But previous models were not able to explain the rather slow rotational velocities of observed single hot subdwarfs. Motivated by recent detections of surface magnetic fields in hot subdwarfs in the range 200 - 500 kiloGauss, we explore in this work the role of large-scale magnetic fields on their rotational evolution via rotating stellar evolution models. We find that large-scale stable magnetic fields can extract angular momentum efficiently from the star via coupling to stellar winds, producing slowly rotating single hot subdwarfs and thus providing a possible explanation to both the long rotation periods provided by asteroseismology and low spectroscopic rotational velocities. This hints magnetic braking could be an important component of the rotational properties of low-mass stellar mergers.
Related
- Magnetic, thermal and rotational evolution of isolated neutron stars
- A three-dimensional exploration of magnetic fields, rotation, and shock revival in a 39 M⊙ core-collapse supernova progenitor
- Second-scale periodicity in FRB 20201124A: Coincident with critical rotation measure evolution epochs and its possible implication
- Cross-correlation between CMB B-modes and Faraday Rotation as a Novel Probe of Primordial Magnetic Fields
- Magnetic contribution to outer-disk rotation in the spiral galaxy NGC 5055
BibTeX
@misc{moyano2026postmerger,
title = {{Post-merger rotational evolution of magnetised single hot subdwarfs results in slow rotation due to magnetic braking}},
author = {Facundo D. Moyano and Zhengwei Liu and Zhanwen Han and Xuefei Chen and Tiara Battich and Philipp Podsiadlowski},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.19671},
eprint = {2610.19671},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.19671},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Post-merger rotational evolution of magnetised single hot subdwarfs results in slow rotation due to magnetic braking
AU - Facundo D. Moyano
AU - Zhengwei Liu
AU - Zhanwen Han
AU - Xuefei Chen
AU - Tiara Battich
AU - Philipp Podsiadlowski
PY - 2026
DA - 2026/10/14
PB - arXiv
DO - 10.48550/arxiv.2610.19671
UR - https://arxiv.org/abs/2610.19671
AB - Single hot subdwarfs are believed to form through mergers of helium-core white dwarfs, which can lead to large-scale magnetic fields generated during the merger, and may be observable at the surface once they evolve into the stable core-helium burning phase. As a post-merger product, the orbital angular momentum of the binary system that forms it, could lead to a rapidly rotating hot subdwarf. But previous models were not able to explain the rather slow rotational velocities of observed single hot subdwarfs. Motivated by recent detections of surface magnetic fields in hot subdwarfs in the range 200 - 500 kiloGauss, we explore in this work the role of large-scale magnetic fields on their rotational evolution via rotating stellar evolution models. We find that large-scale stable magnetic fields can extract angular momentum efficiently from the star via coupling to stellar winds, producing slowly rotating single hot subdwarfs and thus providing a possible explanation to both the long rotation periods provided by asteroseismology and low spectroscopic rotational velocities. This hints magnetic braking could be an important component of the rotational properties of low-mass stellar mergers.
ER -