Old novae and the SW Sex phenomenon

TL;DR

This study reveals that most non-magnetic CVs with periods between 2.8 and 4 hours are SW Sex type with high mass transfer, but some old novae deviate, suggesting nova eruptions influence mass transfer rates.

Contribution

It provides evidence that nova eruptions can cause long-term reductions in mass transfer rates, affecting the classification of CVs within the SW Sex phenomenon.

Findings

Most CVs in 2.8-4h period are SW Sex type with high mass transfer.

Old novae around 3.5h period show low mass transfer, resembling dwarf novae.

Nova eruptions may lead to a hibernation state with reduced mass transfer.

Abstract

From a large observing campaign, we found that nearly all non- or weakly magnetic cataclysmic variables (CVs) in the orbital period range between 2.8 and 4 hours are of SW Sex type and as such experience very high mass transfer rates. The exceptions seem to be some old novae that have periods around 3.5 h. Their spectra do not show the typical SW Sex characteristics but rather resemble those of dwarf novae with low mass transfer rates. The presence of old novae in this period range of SW Sex stars that do not follow the trend but show instead rather low mass transfer rates is interpreted as evidence for an effect of the nova eruption on the mass transfer rate of the underlying CV similar to the hibernation scenario.