The White Dwarf Binary Pathways Survey I: A sample of FGK stars with white dwarf companions

TL;DR

This study identifies and confirms a large sample of FGK main-sequence stars with white dwarf companions using ultraviolet excess detection and Hubble spectroscopy, providing valuable data for binary evolution and supernova research.

Contribution

It presents the first extensive sample of FGK stars with white dwarf companions identified through UV excess, confirmed by Hubble spectra, advancing understanding of binary evolution.

Findings

934 FGK stars with UV excess identified from RAVE and LAMOST surveys.

Hubble spectra confirmed 8 white dwarfs and 1 hot subdwarf among nine systems.

Sample offers a clean dataset for testing binary evolution and supernova models.

Abstract

The number of spatially unresolved white dwarf plus main-sequence star binaries has increased rapidly in the last decade, jumping from only ~30 in 2003 to over 3000. However, in the majority of known systems the companion to the white dwarf is a low mass M dwarf, since these are relatively easy to identify from optical colours and spectra. White dwarfs with more massive FGK type companions have remained elusive due to the large difference in optical brightness between the two stars. In this paper we identify 934 main-sequence FGK stars from the Radial Velocity Experiment (RAVE) survey in the southern hemisphere and the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) survey in the northern hemisphere, that show excess flux at ultraviolet wavelengths which we interpret as the likely presence of a white dwarf companion. We obtained Hubble Space Telescope ultraviolet spectra for nine systems which confirmed that the excess is indeed caused, in all cases, by a hot compact companion, eight being white dwarfs and one a hot subdwarf or pre-helium white dwarf, demonstrating that this sample is very clean. We also address the potential of this sample to test binary evolution models and type Ia supernovae formation channels.