Abstract

Contributed Talk - Splinter CloseBinaries   (MW-0250)

Probing common-envelope evolution with hot subluminous stars in the PLATO era

Gebhardt, A. (1), Heber, U. (1), Geier, S. (2), Dorsch, M. (2), Uzundag, M. (3)
(1) Dr. Remeis-Sternwarte & ECAP, University of Erlangen-Nuremberg, (2) Institut fuer Physik und Astronomie, University of Potsdam, (3) KU Leuven, Belgium

Hot subluminous stars (sdB, sdO, BHB, and ELM white dwarfs) are compact stars, which have lost most of their hydrogen envelopes, on the RGB likely through binary interaction. Thus, they provide a testbed to constrain the formation and evolution of close binaries, common-envelope physics, and the properties of compact companions. We present a well-characterized sample of hot subluminous stars located in the PLATO mission's southern field. Combining Gaia DR3 astrometry with various photometric and spectroscopic surveys, we analyzed spectral energy distributions spanning the UV to infrared to determine stellar radius and luminosity, as well as the identification of main-sequence companions. Our final target list comprises more than 300 bright (G < 17 mag), well-constrained objects. For a subset, spectroscopy from the ESO archive and SDSS-V survey provides surface gravity, helium abundance, and stellar mass when combined with the Gaia DR3 parallax. This sample contains numerous close binaries with white dwarf and low-mass stellar companions, as well as wide post-interaction systems, and many more are expected in the course of the survey. PLATO photometry will enable detailed studies of eclipses, reflection effects, ellipsoidal variations, Doppler beaming, and pulsations, placing stringent constraints on common-envelope ejection and the properties of compact companions.