The formation of low-mass helium white dwarfs in close binaries

TL;DR

This paper discusses the formation of low-mass helium white dwarfs in close binary systems, highlighting recent discoveries and existing discrepancies between observations and theoretical models.

Contribution

It reviews current understanding of low-mass helium white dwarf formation and identifies gaps in theoretical models compared to recent observational data.

Findings

Many low-mass He WDs have been discovered in surveys.

Most have compact object companions.

Discrepancies exist between models and observations.

Abstract

Recently, a large number of low-mass (<0.30 M_sun) helium white dwarfs (He WDs) have been discovered as a result of several surveys campaigns such as WASP, ELM, Kepler or SDSS. The far majority of them have as companion another compact object. There appears to be discrepancies between current theoretical modelling of low-mass He WDs and a number of key observational cases indicating that some details of their formation scenario yet remain to be understood.