Asteroseismic Imprints of Mass Transfer in Binary Stars: Probing the Interiors of Donors and Accretors with Gravity and Acoustic Modes

TL;DR

This paper explores how mass transfer in binary stars leaves detectable signatures in their oscillation modes, enabling insights into internal structures and mass-transfer history through asteroseismology.

Contribution

It provides a detailed analysis of how mass transfer affects g-mode and acoustic mode period spacings, introducing new diagnostic tools for binary star evolution.

Findings

Mass transfer creates chemical gradients affecting g-mode spacings.

Buoyancy glitches induce periodic modulations in g-mode spectra.

Internal sound-speed variations influence acoustic mode frequencies.

Abstract

Context. The synergy between close binary stars and asteroseismology enables constraints on mass-transfer episodes and their consequences for internal structure, rotation profiles, and oscillation modes. Aims. We investigate how mass accretion and donation in close binaries affects the internal structure and oscillation modes of main-sequence stars. Methods. Building on the established relation between the Brunt-Vaisala (buoyancy) glitch and the Fourier spectra of g-mode period spacings, we quantitatively explain the origins of the g-mode period-spacing differences between single-star and mass-accretion/donation models of intermediate-mass stars (M = 2.0, 3.0, and 4.5 Msun). In particular, the hydrogen mass fraction profiles X of the donor model show two chemical gradient regions, which results in a double-peaked Brunt-Vaisala profile. The presence of additional buoyancy glitches gives rise to further periodic modulations in the g-mode period spacings. Results. Mass-accretion induced changes in the chemical profile create sharp features in the buoyancy frequency, which modify both the amplitudes and frequencies of the g-mode period-spacing variations. This behavior resembles that produced by multiple chemical transition zones in compact pulsators such as white dwarfs and sub-dwarf B stars. Similarly, for acoustic modes in the M = 1 Msun solar-like models, we attribute the differences in frequency-separation ratios between single-star and mass-donor models to the variations in the internal sound-speed gradient (acoustic glitches). We discuss future prospects for using asteroseismology to discover the mass-transfer products and constrain the mass-transfer processes in binary star evolution.