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We give an overview of a project aiming to identify new eclipsing post common envelope binaries from the Sloan Digital Sky Survey. This work focuses on the methodology used to identify such systems, describes the follow‐up observations and reports on the results obtained so far.

We present white dwarf mass distributions of a large sample of post common‐envelope binaries and wide white dwarf main sequence binaries and demonstrate that these distributions are statistically independent. While the former contains a much larger fraction of low‐mass white dwarfs, the latter is similar to single white dwarf mass distributions. Taking into account observational biases we also show that the majority of low‐mass white dwarfs are formed in close binaries.

The project Massive Unseen Companions to Hot Faint Underluminous Stars from SDSS (MUCHFUSS) aims at finding hot subdwarf stars with massive compact companions like massive white dwarfs (M>1.0 M⊙), neutron stars or stellar mass black holes. The existence of such systems is predicted by binary evolution theory and recent discoveries indicate that they exist in our Galaxy. We classified about 1500 hot subdwarf stars from the Sloan Digital Sky Survey (SDSS) by colour selection and visual inspection of their spectra. Stars with high velocities have been reobserved and individual SDSS spectra have been analysed. In total ≃170 radial velocity variable subdwarfs have been discovered and ≃80 of them have been selected as good candidates for follow‐up time resolved spectroscopy to derive their orbital parameters. Up to now we found seven close binary sdBs with short orbital periods ranging from ≃0.21 d to 1.5 d. In our photometric follow‐up campaign we discovered two eclipsing binaries with companions, that are mor...

Nonradial pulsations had ceased in the accreting white dwarf SDSS J074531.92+453829.6 subsequent to its October 2006 outburst. We recently acquired optical high‐speed time‐series photometry on this cataclysmic variable more than three years after its outburst to find that pulsations have now returned to the primary white dwarf. Moreover, the observed pulsation periods agree with pre‐outburst periods within the uncertainties of 1–2 s. This discovery is both remarkable and significant because it indicates that the outburst did not affect the interior stellar structure, which dictates the observed pulsation frequencies. Using this discovery in addition to an HST ultra‐violet temperature measurement obtained one year after outburst, we have also been able to constrain the matter accreted during the 2006 outburst.

The project Massive Unseen Companions to Hot Faint Underluminous Stars from SDSS (MUCHFUSS) aims at finding hot subdwarf stars with massive compact companions like supermassive white dwarfs (M>1.0M⊙), neutron stars or stellar mass black holes. The existence of such systems is predicted by binary evolution theory and recent discoveries indicate that they exist in our Galaxy. We classified about 1500 hot subdwarf stars from the Sloan Digital Sky Survey (SDSS) by colour selection and visual inspection of their spectra. Stars with high velocities have been reobserved and individual SDSS spectra have been analysed. In total about 170 radial velocity variable subdwarfs have been discovered and about 80 of them have been selected as good candidates for follow‐up time resolved spectroscopy to derive their orbital parameters. Up to now we found seven close binary sdBs with short orbital periods ranging from ≃0.21 d to 1.5 d. In our photometric follow‐up campaign we discovered two eclipsing binaries with most likel...