Late evolution stages of CVs

According to standard evolutionary theory, CVs evolve from longer to shorter orbital periods until a minimum period is reached (Pmin~76 min). The properties of the secondary star here are expected to change dramatically. Systems that have passed beyond Pmin 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.