The formation of Cataclysmic Variables: the influence of nova eruptions

TL;DR

This paper explores how nova eruptions influence the formation and evolution of cataclysmic variables, highlighting effects on mass transfer stability, orbital eccentricity, and potential observable consequences.

Contribution

It introduces models of nova-induced mass ejection effects, including common-envelope interactions and asymmetry, on CV formation and evolution, which were not thoroughly examined before.

Findings

Common-envelope ejection reduces mass transfer stability, especially in low-mass white dwarfs.

Asymmetric mass ejection can induce orbital eccentricity, affecting short-period systems.

Mass transfer rates increase, potentially leading to observable phenomena in CVs.

Abstract

The theoretical and observed populations of pre-cataclysmic variables (pre-CVs) are dominated by systems with low-mass white dwarfs (WDs), while the WD masses in CVs are typically high. In addition, the space density of CVs is found to be significantly lower than theoretical models. We investigate the influence of nova outbursts on the formation and (initial) evolution of CVs. In particular, we calculate the stability of the mass transfer in case all the material accreted on the WD is lost in classical novae, and part of the energy to eject the material comes from a common-envelope like interaction with the companion. In addition, we study the effect of an asymmetry in the mass ejection, that may lead to small eccentricities in the orbit. We find that a common-envelope like ejection significantly decreases the stability of the mass transfer, in particular for low-mass WD. Similarly, the influence of asymmetric mass loss can be important for short-period systems and even more so for low-mass WD, but likely disappears long before the next nova outburst due to orbital circularization. In both cases the mass-transfer rates increase, which may lead to observable (and perhaps already observed) consequences for systems that do survive to become CVs. However, a more detailed investigation of the interaction between nova ejecta and the companion and the evolution of slightly eccentric CVs is needed before definite conclusions can be drawn.