Nova-produced Common Envelope: Source of the Non-solar Abundances and an Additional Frictional Angular Momentum Loss in Cataclysmic Variables

TL;DR

This paper proposes that nova-produced common envelopes around white dwarfs in cataclysmic variables contribute non-solar abundances and cause additional angular momentum loss, affecting their evolution and observed properties.

Contribution

It introduces the novel idea that nova-formed common envelopes significantly influence CV composition and angular momentum dynamics, explaining several observational phenomena.

Findings

Nova-produced common envelopes contain non-solar material.

Re-accretion of envelope material alters secondary star composition.

Frictional angular momentum loss explains CV period changes and distribution.

Abstract

A substantial fraction of Cataclysmic Variables (CVs) reveals non-solar abundances. A comprehensive list of CVs which includes those that have been examined for these abundances is given. Three possible sources of these non-solar abundances on the secondary are accretion during the red giant common envelope phase, an Evolved Main Sequence secondary and nova-processed material. Use of the secondary's cross-section just on the escaping nova material to change the abundances of its convective region has been the killing objection for considering nova-processed material. The key element, ignored in other studies, is that a thermonuclear runaway on a white dwarf causes a strong propagating shock wave which not only ejects material, but also produces a large amount of non-ejected material which forms a common envelope. This nova-produced common envelope contains a large amount of non-solar material. We demonstrate that the secondary has the capacity and time to re-accrete enough of this material to acquire a significant non-solar convective region. This same envelope interacting with the binary will produce a Frictional Angular Momentum Loss which can be the Consequential Angular Momentum Loss needed for the average CV white dwarf mass, WD mass accretion rates, the period minimum, the orbital period distribution, and the space density of CVs problems. This interaction will decrease the orbital period which can cause the recently observed sudden period decreases across nova eruptions. A simple, rapid evolutionary model of the secondary that includes the swept-up nova-produced material and the increasing convective region is developed and applied to individual CVs.