The Asteroseismic Imprints of Mass Transfer: A Case Study of a Binary Mass Gainer in the SPB Instability Strip

Abstract: We present new simulations investigating the impact of mass transfer on the asteroseismic signals of slowly pulsating B stars. We use MESA to simulate the evolution of a binary star system and GYRE to compute the asteroseismic properties of the accretor star. We show that, compared to a single star of the same final mass, a star that has undergone accretion (of non-enriched material) has a significantly different internal structure, evident in both the hydrogen abundance profile and Brunt-V\"ais\"al\"a frequency profile. These differences result in significant changes in the observed period spacing patterns, implying that one may use this as a diagnostic to test whether a star's core has been rejuvenated as a result of accretion. We show that it is essential to consider the full multimodal posterior distributions when fitting stellar properties of mass-gainers to avoid drawing misleading conclusions. Even with these considerations, stellar ages will be significantly underestimated when assuming single star evolution for a mass-gainer. We find that future detectors with improved uncertainties would rule out single star models with the correct mass and central hydrogen fraction. Our proof of principle analysis demonstrates the need to further investigate the impact of binary interactions on stellar asteroseismic signals for a wide range of parameters, such as initial mass, amount of mass transferred and the age of the accretor star at the onset of mass transfer.