Speaker
Description
Period-bounce cataclysmic variables (CVs) are systems where a white dwarf accretes from a brown dwarf donor, having reached a point where the degeneracy of the donor reverses the orbit period evolution. A large portion of the CV population, between 40$\%$ and 70$\%$, is predicted to be made up of period-bouncers. However, due to their intrinsic faintness, only on the order of a dozen such systems have been confidently identified so far. A promising approach to identify period-bounce CVs is an X-ray detection. It provides proof of accretion from the substellar companion onto the white dwarf because the coronal emission of a brown dwarf donor is below the sensitivity of current instruments.
We have compiled a literature catalogue of CVs around the period-bounce, including known period-bouncers, containing 213 systems. We characterized this elusive subclass of CVs using values available in the literature for system parameters (including orbital period, mass and spectral type of the donor, and white dwarf temperature) as well as multi-wavelength photometry. The main result is a "scorecard" assigning to each system the probability of being a period-bouncer. We systematically analysed X-ray data from the recent all-sky surveys carried out with the extended ROentgen Survey with an Imaging Telescope Array (eROSITA) onboard the Spektrum-Roentgen-Gamma spacecraft (SRG). Using this information we confirm 12 systems as new period-bouncers, raising their population by $\sim 70\%$. We provide an outlook of the eROSITA all-sky survey capabilities for the X-ray detection of previously unknown period-bouncers.
