Very Late Thermal Pulses Influenced by Accretion in Planetary Nebulae

TL;DR

This paper explores how accretion of backflowing mass in planetary nebulae can influence very late thermal pulses, potentially triggering them and affecting their symmetry and ejection properties.

Contribution

It introduces the idea that backflowing mass can form accretion disks around central stars, impacting VLTP occurrence and characteristics.

Findings

Accreted mass can form transient disks influencing VLTP.

Backflow may trigger or modify VLTP events.

Accretion affects symmetry of mass ejection.

Abstract

We consider the possibility that a mass of ~10^{-5}-10^{-3} Msun flows back from the dense shell of planetary nebulae and is accreted by the central star during the planetary nebula phase. This backflowing mass is expected to have a significant specific angular momentum even in (rare) spherical planetary nebulae, such that a transient accretion disk might be formed. This mass might influence the occurrence and properties of a very late thermal pulse (VLTP), and might even trigger it. For example, the rapidly rotating outer layer, and the disk if still exist, might lead to axisymmetrical mass ejection by the VLTP. Unstable burning of accreted hydrogen might result in a mild flash of the hydrogen shell, also accompanied by axisymmetrical ejection.