Late evolution stages of CVs

According to standard evolutionary theory, CVs evolve from longer to shorter orbital periods until a minimum period is reached (P_min~76 min). The properties of the secondary star here are expected to change dramatically. Systems that have passed beyond P_min are evolving back toward longer periods, with the donor star now extremely dim. This has long been predicted to be the “graveyard” and current state of 70% of all
CVs, however only very few more or less robust candidates for such a period bouncer system have been identified until now. I have been working to improve this situation shedding light into the late evolution stages of CVs through the observation of interesting short period binaries (for example, SDSS
J080434.20+510349.2 and SDSS J123813.73-033933.0 – Zharikov et al. 2006, 2006; Aviles et al. 2010; SSS J122221.7-311525 – Neustroev et al. 2017). These systems frequently exhibit in their optical spectra signatures of a faint accretion disc and the underlying white dwarf, so they are ideal targets for spectral modelling and determination of stellar parameters.