Speaker: Anna Francesca Pala (ESO)
Title: The properties of the galactic population of cataclysmic variables from Gaia DR2
Abstract: Cataclysmic variables (CVs) are close interacting binaries containing a white dwarf accreting from a low-mass main sequence star. CVs are the best type of systems to test our understanding of the evolution of compact, interacting binaries, as they are numerous, relatively bright, and both stellar components are structurally simple. Nonetheless, there are a number of discrepancies between the current models of CV evolution and the observations that undermine our confidence in understanding the evolution and formation of more complex systems, such as black hole binaries, X-ray transients or SN Ia progenitors. The most striking disagreements are: (i) the predicted CV space density (de Kool 1992) is about 1-2 order of magnitude higher than observed; (ii) the observed average mass of CV white dwarfs is significantly higher (~0.8 Msun, Zorotovic et al. 2011) than predicted by binary population synthesis studies (<0.6 Msun, Politano 1996). Using the second Gaia data release (DR2), we carry out the first population study of a volume-limited sample of CVs to accurately constrain their space density. In addition, by combining the distance to the systems with archival ultraviolet spectroscopy we are able to derive precise measurements of the masses of the white dwarf. In this talk, I will discuss the results from this study in the context of the current models of compact binary evolution.