Episodic mass transfer: A trigger for nova outbursts?

TL;DR

This paper proposes that episodic mass transfer from the secondary star triggers nova outbursts by forming circumbinary gas and accretion onto the white dwarf, explaining spectral features and suggesting a secular increase in WD mass.

Contribution

It introduces a novel model linking episodic mass transfer to nova outbursts and predicts observable spectral signatures distinct from previous theories.

Findings

Spectral components correspond to episodic mass transfer events.

Collision of ejecta with circumbinary gas explains spectral line velocities.

Secular increase in white dwarf mass is implied.

Abstract

High resolution spectra of postoutburst novae show multiple components of ejected gas that are kinematically distinct. We interpret the observations in terms of episodes of enhanced mass transfer originating from the secondary star that result in the formation of discrete components of circumbinary gas and accretion onto the WD that trigger nova outbursts. In this picture the concordance between absorption line velocities and emission line widths in most novae occurs as a result of the collision of the expanding nova ejecta with a larger mass of surrounding circumbinary gas. One implication of this model is that much of the accreted gas remains on the WD, leading to a secular increase in WD mass over each outburst event. Alternative scenarios to explain nova spectral evolution are possible that do not invoke circumbinary gas and a possible test of different models is proposed.