Abstract

Contributed Talk - Splinter CloseBinaries   (MW-0250)

Short-period binary hot subdwarfs: a complete census within 500pc

H. Dawson¹, M. Dorsch¹, J. Munday¹ et al.
Institute for Physics and Astronomy, University of Potsdam

Hot subdwarf stars are compact, typically helium-burning stars that have shed nearly all of their hydrogen envelopes. Despite decades of study, their formation is not yet fully understood. The leading channels involve binary interaction: a common-envelope phase produces short-period systems, stable Roche-lobe overflow produces long-period ones, and mergers of two helium white dwarfs account for at least some of the apparently single population. The short-period binary fraction is therefore a key observable because it directly traces the conditions under which mass transfer becomes unstable and a common envelope is ejected. In this talk, I present the most complete census of short-period hot subdwarf binaries to date, drawn from a volume-complete sample of 301 stars within 500 pc using Gaia DR3 parallaxes and radial-velocity follow-up. We deliver orbital solutions for 34 newly identified systems, filling a previously under-represented gap in the 1-20 day period range. Breaking the binary fraction down by spectral class reveals clear inhomogeneity, hinting at distinct evolutionary pathways for some sub-populations. Finally, a handful of these compact binaries are expected to qualify as Type Ia supernova progenitors via double-detonation or double-degenerate merger channels. Leveraging the volume completeness of our sample, we place the first observationally-grounded constraints on the contribution of hot subdwarf binaries to the Galactic supernova rate.