Effects of limited core rejuvenation on the properties of massive contact binaries

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Main Authors: Vandersnickt, Jelle, Fabry, Matthias
Format: Preprint
Published: 2025
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author Vandersnickt, Jelle
Fabry, Matthias
author_facet Vandersnickt, Jelle
Fabry, Matthias
contents Context. Massive contact binaries are both stellar merger and gravitational wave progenitors, but their evolution is still uncertain. An open problem in the population synthesis of massive contact binaries is the predicted mass ratio distribution. Current simulations evolve quickly to mass ratios close to unity, which is not supported by the sample of observed systems. It has been shown that modifying the near core mixing properties of massive stars can alter the evolution of contact binaries, but it has not been tested on a whole population. Aims. We implement a prescription of the convective core overshooting based on the molecular gradient. The goal of the implementation is to limit the rejuvenation efficiency of the accretor. We aim to investigate the effects of the reduced rejuvenation on the mass ratio distribution of massive contact binaries. Methods. We calculate a grid of 4896 models with the binary-evolution code MESA with our convective overshoot formulation, and we compare the simulations with the known observations of massive contact binaries. Results. We find that by limiting the core rejuvenation through the convective core overshoot, the predicted mass-ratio distribution shifts significantly to values away from unity. This improves the theoretical predictions of the mass ratios of massive contact binaries. Conclusions. The core rejuvenation of the components in massive contact binaries is a key parameter for their predicted mass ratio distribution. Establishing the rejuvenation efficiency with the contact binary population should therefore be possible. The sample size and uncertainties associated to the characterization of contact binaries however prevents us from doing so, and other methods like asteroseismology can place constraints on the rejuvenation process.
format Preprint
id arxiv_https___arxiv_org_abs_2502_17544
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Effects of limited core rejuvenation on the properties of massive contact binaries
Vandersnickt, Jelle
Fabry, Matthias
Solar and Stellar Astrophysics
High Energy Astrophysical Phenomena
Context. Massive contact binaries are both stellar merger and gravitational wave progenitors, but their evolution is still uncertain. An open problem in the population synthesis of massive contact binaries is the predicted mass ratio distribution. Current simulations evolve quickly to mass ratios close to unity, which is not supported by the sample of observed systems. It has been shown that modifying the near core mixing properties of massive stars can alter the evolution of contact binaries, but it has not been tested on a whole population. Aims. We implement a prescription of the convective core overshooting based on the molecular gradient. The goal of the implementation is to limit the rejuvenation efficiency of the accretor. We aim to investigate the effects of the reduced rejuvenation on the mass ratio distribution of massive contact binaries. Methods. We calculate a grid of 4896 models with the binary-evolution code MESA with our convective overshoot formulation, and we compare the simulations with the known observations of massive contact binaries. Results. We find that by limiting the core rejuvenation through the convective core overshoot, the predicted mass-ratio distribution shifts significantly to values away from unity. This improves the theoretical predictions of the mass ratios of massive contact binaries. Conclusions. The core rejuvenation of the components in massive contact binaries is a key parameter for their predicted mass ratio distribution. Establishing the rejuvenation efficiency with the contact binary population should therefore be possible. The sample size and uncertainties associated to the characterization of contact binaries however prevents us from doing so, and other methods like asteroseismology can place constraints on the rejuvenation process.
title Effects of limited core rejuvenation on the properties of massive contact binaries
topic Solar and Stellar Astrophysics
High Energy Astrophysical Phenomena
url https://arxiv.org/abs/2502.17544