The evolutionary and asteroseismic imprints of mass accretion. The 10 M${}_{\odot }$ $\beta$ Cep case study

Abstract

We investigate the structural and asteroseismic consequences of mass accretion in massive stars within close binary systems. Using MESA, we model the evolution of the 10 M${}_{\odot }$ accretor through and after a Roche lobe overflow phase. In addition to changing the surface composition of the star, mass accretion also significantly modifies the internal structure by expanding the convective core and altering chemical stratification near the core-envelope boundary. This partial core rejuvenation creates a distinct mean molecular weight gradient and leaves a persistent local density modulation. In the late stages of mass transfer, changes in density and sound-speed profiles become apparent and influence stellar oscillations. We analyse the asteroseismic properties of the post-mass transfer models compared to single stars of the same mass and central hydrogen abundance. In the gravity mode regime, the altered Brunt-Väisälä frequency leads to period spacing patterns with larger amplitudes and phase shifts. For low and intermediate-order pressure modes, we find systematic frequency deviations linked to changes in the sound-speed profile. Weight function analyses confirm that these differences arise primarily from structural modifications near the convective core boundary. Furthermore, small frequency separations, sensitive to localised sound-speed gradients, reveal periodic variations attributable to the density discontinuity at the convective core edge. The accretor exhibits a larger sound-speed gradient integral and a longer acoustic radius ratio compared to the single star, consistent with its expanded core. Our results demonstrate that mass accretion imprints measurable asteroseismic signatures on both gravity and pressure modes. These signatures provide powerful diagnostics for identifying post-interaction stars, for refining stellar age and structure estimates in binary systems.

Accepted for publication in A&A

References in corpus (19)

• Modules for Experiments in Stellar Astrophysics (MESA)
• The Transiting Exoplanet Survey Satellite
• Binary interaction dominates the evolution of massive stars
• Modules for Experiments in Stellar Astrophysics (MESA): Pulsating Variable Stars, Rotation, Convective Boundaries, and Energy Conservation
• Updated Electron-Conduction Opacities: The Impact on Low-Mass Stellar Models
• Probing the properties of convective cores through g modes: high-order g modes in SPB and gamma Doradus stars
• Angular momentum transport by heat-driven g-modes in slowly pulsating B stars
• Coulomb tunneling for fusion reactions in dense matter: Path integral Monte Carlo versus mean field
• Thermohaline mixing and gravitational settling in carbon-enhanced metal-poor stars
• Asteroseismic masses, ages, and core properties of $\gamma$ Doradus stars using gravito-inertial dipole modes and spectroscopy
• Asteroseismic estimate of helium abundance of a solar analog binary system
• The Contour Method: a new approach to finding modes of non-adiabatic stellar pulsations
• Pulsational Instabilities in Accreting White Dwarfs
• KIC 8262223: A Post-Mass Transfer Eclipsing Binary Consisting of a Delta Scuti Pulsator and a Helium White Dwarf Precursor
• gyre_tides: Modeling binary tides within the gyre stellar oscillation code
• The eclipsing binary systems with $\delta$ Scuti component. I. KIC 10661783
• Acoustic modes in M67 cluster stars trace deepening convective envelopes
• The theoretical pulsation spectra of hot B subdwarfs. Static and evolutionary STELUM models
• Off-centre convective zones in mass accreting stellar models