White dwarf - main sequence star collisions from wide triples in the field

TL;DR

This paper investigates how wide triple star systems in the galactic field can become dynamically unstable, leading to collisions or mergers between white dwarfs and main sequence stars, with potential observable supernova-like events.

Contribution

It provides the first detailed calculation of collision and merger rates in wide triples involving white dwarfs and main sequence stars, considering galactic field interactions.

Findings

Calculated collision rate between MS and WD stars.

Estimated merger rate of double WDs.

Discussed potential observability of collision events.

Abstract

Multiple star systems interact strongly with Galactic field stars when the outer semi-major axis of a triple or multiple star is > 10 3 AU. Stable triples composed of two white-dwarfs (WD) and a low mass main sequence (MS) star in a wide outer orbit can thus be destabilized by gravitational interactions with random field stars. Such interactions excite the eccentricity of the distant third star sufficiently so that it begins to interact significantly with the inner binary. When this occurs the triple undergoes multiple binary-single resonant encounters. These encounters may result either in a collision between the nondegenerate component and a WD, or the breakup of the triple into a compact binary and a third object which is ejected. The compact binary can be either a MS-WD pair which survives, or collides, or a double WD which may inspiral through gravitational wave emission. We calculate the collision rate between a MS and WD star, and the merger rate of double WDs. Additionally, we describe the prospects of detectability of such a collision, which may resemble a sub-luminous SN event.