Cataclysmic Variables from Sloan Digital Sky Survey V -- the search for period bouncers continues

TL;DR

This study analyzes SDSS-V data to identify and characterize cataclysmic variables, revealing a lack of clear period gaps and very few period bouncers, thus providing insights into CV evolution and population density.

Contribution

It reports the discovery of new CVs, refutes some previous candidates, and provides the first estimates of period bouncer density in the SDSS-V sample.

Findings

No clear period gap in SDSS-V CVs

Very few period bouncers found, constituting a few percent of CVs

Estimated space density of period bouncers is approximately 0.2×10^{-6} pc^{-3}

Abstract

SDSS-V is carrying out a dedicated survey for white dwarfs, single and in binaries, and we report the analysis of the spectroscopy of cataclysmic variables (CVs) and CV candidates obtained during the final plug plate observations of SDSS. We identify eight new CVs, spectroscopically confirm 53 and refute eleven published CV candidates, and we report 21 new or improved orbital periods. Combined with previously published data, the orbital period distribution of the SDSS-V CVs does not clearly exhibit a period gap. This is consistent with previous findings that spectroscopically identified CVs have a larger proportion of short-period systems compared to samples identified from photometric variability. Remarkably, despite a systematic search, we find very few period bouncers. We estimate the space density of period bouncers to be $\simeq0.2\times10^{-6}\,\mathrm{pc}^{-3}$, i.e. they represent only a few per cent of the total CV population. This suggests that during their final phase of evolution, CVs either destroy the donor, e.g. via a merger, or that they become detached and cease mass transfer.