To search for hot subdwarf stars in close binary systems and single stars with very high velocities, we first compiled of an all-sky catalogue of essentially all known sdO/B stars consisting of more than 4400 stars.
Since close binary stars show characteristic variability in their light curves caused by eclipses and tidal effect, we visually inspected light curve data from the following surveys aimed to find exoplanets or astrophysical transients such as supernovae: Catalina Real Time Survey (completed), Palomar Transient Factory (completed in collaboration with T. Kupfer, Caltech), SuperWASP (ongoing), GALEX gPhoton (ongoing in collaboration with D. Wilson, Warwick). In this way we discovered about 20 new sdBs with low-mass stellar companions, several pulsating sdBs and one short-period sdB+WD binary. However, we found that systematics in the light curves limit the sensitivity to discover sdB+WD systems with shallow variations. Especially the systematics in the gPhoton light curves must be examined further.
To find high velocity we cross-matched the sdO/B catalogue with proper motion catalogues and found 65 hot subdwarfs with high velocities between >300-900 km/s. To obtain spectra of the best candidates we prepared proposals for observing time at the Gemini, William Herschel, SOAR and VLT telescopes.
Overview of the results:
* A new catalogue of hot subdwarf stars
* Discovery of a sample of variable hot subwdarf binaries, among them one potential candidate for being the progenitor of an SN Ia
* Discovery of a significant number of high velocity hot subdwarfs, which might be the ejected companions of SN Ia
Due to the early termination of the project (five months after the start of this Marie Curie action), these early results have not been published within its duration. Subsequently, however, we published an extended version of the hot subdwarf catalogue (Geier et al. 2017, A&A, accepted) and the close binary sdB+WD system we found (Kupfer et al. 2017, ApJ, 835, 131).
