Hot Subdwarfs from the Stable Roche Lobe Overflow Channel

TL;DR

This paper investigates the formation and evolution of hot subdwarfs via stable Roche lobe overflow in intermediate-mass binaries, providing insights into their properties and potential observational signatures.

Contribution

It offers a comprehensive analysis of hot subdwarfs formation through stable RLOF, including initial parameter ranges and properties, with novel predictions of high-mass subdwarfs in binaries.

Findings

Hot subdwarfs can form through stable RLOF at main sequence and Hertzsprung gap phases.

Some subdwarf B/OB stars may have anomalously high masses (~1 solar mass) with thick envelopes.

Predictions suggest hot subdwarfs in binary systems could be observed in open clusters.

Abstract

In this study, we concentrate on the formation and evolution of hot subdwarfs binaries through the stable Roche lobe overflow (RLOF) channel of intermediate-mass binaries. We aim at setting out the properties of hot subdwarfs and their progenitors, so that we can understand the formation and evolution of hot subdwarfs comprehensively. We have obtained the ranges of the initial parameters of progenitor binaries and the properties of hot subdwarfs through the stable RLOF channel of intermediate-mass binaries, e.g. mass, envelope mass and age of hot subdwarfs. We have found that hot subdwarfs could be formed through the stable Roche lobe overflow at main sequence and Hertzsprung gap. We have also found that some subdwarf B or OB stars have anomalous high mass (around 1 solar mass) with thick envelope (0.07 solar mass to 0.16 solar mass) in our models. By comparing our theoretical results with observations on the hot subdwarfs in open clusters, we suppose a quantity of hot subdwarfs in binary systems might be found in open clusters in the future.