A Be Star + He Star Binary as an Indicator of a Binary Mass Transfer Phase

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Main Authors: Bao, Yuchen, Li, Zhenwei, Ge, Hongwei, Chen, Xuefei, Han, Zhanwen
Format: Preprint
Published: 2025
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author Bao, Yuchen
Li, Zhenwei
Ge, Hongwei
Chen, Xuefei
Han, Zhanwen
author_facet Bao, Yuchen
Li, Zhenwei
Ge, Hongwei
Chen, Xuefei
Han, Zhanwen
contents The rapid rotation of Be stars is supposed to mainly originate from binary evolution. In recent years, more and more Be stars with helium (He) star companions have been discovered, which provides a significant opportunity to study binary interaction physics. In this work, we perform binary population synthesis with an updated binary mass transfer stability criterion and try to understand the details of mass transfer processes by constructing a series of Be star + He star (BeHe) binary populations. We found that the simulations and the observations can be divided into two groups according to the masses of components, corresponding to the two distinct evolutionary processes during the mass transfer. In particular, we found that the mass ratios of BeHe binaries may be taken as a probe of the initial mass ratios of the primordial binaries. Moreover, the results suggest that a higher mass transfer efficiency ($\gtrsim 0.5$) supports the observations better. The simulations predicted too many Be star binaries experiencing Case B mass transfer, which conflicts with the observations. The reason is due to either observational selection effects or unclear physical factors.
format Preprint
id arxiv_https___arxiv_org_abs_2506_02662
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle A Be Star + He Star Binary as an Indicator of a Binary Mass Transfer Phase
Bao, Yuchen
Li, Zhenwei
Ge, Hongwei
Chen, Xuefei
Han, Zhanwen
Solar and Stellar Astrophysics
The rapid rotation of Be stars is supposed to mainly originate from binary evolution. In recent years, more and more Be stars with helium (He) star companions have been discovered, which provides a significant opportunity to study binary interaction physics. In this work, we perform binary population synthesis with an updated binary mass transfer stability criterion and try to understand the details of mass transfer processes by constructing a series of Be star + He star (BeHe) binary populations. We found that the simulations and the observations can be divided into two groups according to the masses of components, corresponding to the two distinct evolutionary processes during the mass transfer. In particular, we found that the mass ratios of BeHe binaries may be taken as a probe of the initial mass ratios of the primordial binaries. Moreover, the results suggest that a higher mass transfer efficiency ($\gtrsim 0.5$) supports the observations better. The simulations predicted too many Be star binaries experiencing Case B mass transfer, which conflicts with the observations. The reason is due to either observational selection effects or unclear physical factors.
title A Be Star + He Star Binary as an Indicator of a Binary Mass Transfer Phase
topic Solar and Stellar Astrophysics
url https://arxiv.org/abs/2506.02662