Asteroseismic imprints of mass transfer in binary stars: Probing the interiors of donors and accretors with gravity and acoustic modes

¹ Yunnan Observatories, Chinese Academy of Sciences, 396 Yangfangwang Guandu District Kunming 650216, PR China
² Key Laboratory for the Structure and Evolution of Celestial Objects, Chinese Academy of Sciences, 396 Yangfangwang Guandu District Kunming 650216, PR China
³ International Centre of Supernovae, Yunnan Key Laboratory, 396 Yangfangwang Guandu District Kunming 650216, PR China
⁴ University of Chinese Academy of Sciences Beijing 100049, PR China
⁵ Center for Astronomical Mega-Science, Chinese Academy of Sciences, 20A Datun Road Chaoyang District Beijing 100012, PR China
⁶ Institute of Astronomy (IvS), KU Leuven Celestijnenlaan 200D B-3001 Leuven, Belgium
⁷ Department of Applied Mathematics, School of Mathematics, University of Leeds Leeds LS2 9JT, UK

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Received: 5 November 2025
Accepted: 17 November 2025

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–Väisälä (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 or donation models of intermediate-mass stars (M = 2.0, 3.0, and 4.5 M_⊙). In particular, the hydrogen mass fraction profiles X of the donor model show two chemical gradient regions, which results in a double-peaked Brunt–Väisälä 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 behaviour 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 M_⊙ 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 of using asteroseismology to discover the mass-transfer products and constrain the mass-transfer processes in binary star evolution.