OC25_10_29_Leen_Decin_Unveiling Close-In Companions to Evolved Stars via (sub)mm Interferometry

Описание: Close-in companions play a fundamental role in shaping the evolution of their host stars, influencing mass loss, tidal interactions, and mass transfer across all evolutionary stages. While close companions—including planets—have been frequently observed around young stellar objects, main-sequence stars, red giants, and compact objects, direct observational evidence of companions within a few stellar radii of asymptotic giant branch (AGB) stars has remained elusive. I present new (sub)millimeter time-domain proper motion and imaging spectroscopy data that enabled the first direct detection of a close-in companion in Keplerian motion around an AGB star. By combining these data with optical observations, we determined the full orbital solution, including separation, inclination, and barycentric proper motion. The companion’s inferred current mass exceeds that of the AGB star and indicates it is either an F6–F8V main-sequence star or a massive white dwarf. Unlike more evolved stars with companions at comparable distances, this companion follows a circular orbit, suggesting an eccentricity-generating mechanism at the end of or beyond the AGB phase. I discuss how the retrieved orbital parameters serve as a critical benchmark for stellar and binary evolution models and reveal tensions in tidal interaction physics. This work also demonstrates the potential of multi-epoch (sub)millimeter imaging, especially when combined with Gaia DR4 optical astrometry, to provide precise orbital constraints for evolved binaries. Such synergy will significantly advance our understanding of tidal interactions, mass transfer, and orbital evolution in giant binary systems—key processes that shape the life cycles of stars in diverse astrophysical environments.