Triggering micronovae through magnetically confined accretion flows in accreting white dwarfs

TL;DR

This paper proposes a model where magnetic confinement in accreting white dwarfs triggers localized thermonuclear runaways, explaining rapid optical bursts called micronovae, especially in systems with high mass and transfer rates.

Contribution

It introduces a novel model linking magnetic confinement to micronovae, enhancing understanding of burst triggers in accreting white dwarfs.

Findings

Magnetic confinement can trigger localized thermonuclear runaways.

Micronovae are more likely in systems with high white dwarf mass.

The model explains the observed properties of micronovae.

Abstract

Rapid bursts at optical wavelengths have been reported for several accreting white dwarfs, where the optical luminosity can increase by up to a factor 30 in less than an hour fading on timescales of several hours, and where the energy release can reach $\approx10^{39}$ erg ("micronovae"). Several systems have also shown these bursts to be semi-recurrent on timescales of days to months and the temporal profiles of these bursts strongly resemble those observed in Type-I X-ray bursts in accreting neutron stars. It has been suggested that the observed micronovae may be the result of localised thermonuclear runaways on the surface layers of accreting white dwarfs. Here we propose a model where magnetic confinement of the accretion stream on to accreting magnetic white dwarfs may trigger localised thermonuclear runaways. The proposed model to trigger micronovae appears to favour magnetic systems with both high white dwarf masses and high mass-transfer rates.