The predicted and observed space density of cataclysmic variables (CVs) have been for a long time discrepant by at least an order of magnitude. The standard model of CV evolution predicts that the vast majority of CVs should be period bouncers, whose space density has been recently measured to be ρ 2 × 10 −5 pc −3 . We performed population synthesis of CVs using an updated version of the Binary Stellar Evolution (BSE) code for single and binary star evolution. We find that the recently suggested empirical prescription of consequential angular momentum loss (CAML) brings into agreement predicted and observed space densities of CVs and period bouncers. To progress with our understanding of CV evolution it is crucial to understand the physical mechanism behind empirical CAML. Our changes to the BSE code are also provided in details, which will allow the community to accurately model mass transfer in interacting binaries in which degenerate objects accrete from low-mass main-sequence donor stars.

Constraints from surveys of post-common envelope binaries (PCEBs) consisting of a white dwarf plus an M-dwarf companion have led to significant progress in our understanding of the formation of close white dwarf binary stars with low-mass companions. The white dwarf binary pathways project aims at extending these previous surveys to larger secondary masses, i.e. secondary stars of spectral-type AFGK. Here, we present the discovery and observational characterization of three PCEBs with G-type secondary stars and orbital periods between 1.2 and 2.5 d. Using our own tools as well as MESA, we estimate the evolutionary history of the binary stars and predict their future. We find a large range of possible evolutionary histories for all three systems and identify no indications for differences in common envelope evolution compared to PCEBs with lower mass secondary stars. Despite their similarities in orbital period and secondary spectral type, we estimate that the future of the three systems is very different: TYC 4962-1205-1 is a progenitor of a cataclysmic variable system with an evolved donor star, TYC 4700-815-1 will run into dynamically unstable mass transfer that will cause the two stars to merge, and TYC 1380-957-1 may appear as supersoft source before becoming a rather typical cataclysmic variable star.

Atmospheric escape from close-in Neptunes and hot Jupiters around sun-like stars driven by extreme ultraviolet (EUV) irradiation plays an important role in the evolution of exo-planets and in shaping their ensemble properties. Intermediate and low mass stars are brightest at EUV wavelengths at the very end of their lives, after they have expelled their envelopes and evolved into hot white dwarfs. Yet the effect of the intense EUV irradiation of giant planets orbiting young white dwarfs has not been assessed. We show that the giant planets in the solar system will experience significant hydrodynamic escape caused by the EUV irradiation from the white dwarf left behind by the Sun. A fraction of the evaporated volatiles will be accreted by the solar white dwarf, resulting in detectable photospheric absorption lines. As a large number of the currently known extra-solar giant planets will survive the metamorphosis of their host stars into white dwarfs, observational signatures of accretion from evaporating planetary atmospheres are expected to be common. In fact, one third of the known hot single white dwarfs show photospheric absorption lines of volatile elements, which we argue are indicative of ongoing accretion from evaporating planets. The fraction of volatile contaminated hot white dwarfs strongly decreases as they cool. We show that accretion from evaporating planetary atmospheres naturally explains this temperature dependence if more than 50 per cent of hot white dwarfs still host giant planets.