The Binary Fraction of Low Mass White Dwarfs

TL;DR

This study investigates the binary fraction of low-mass white dwarfs, finding less than 30% are single, and explores possible formation channels beyond binary mergers, including stellar winds and substellar interactions.

Contribution

It provides spectroscopic data and analysis on the binary status of low-mass white dwarfs, highlighting the need for alternative formation scenarios.

Findings

Less than 30% of low-mass WDs are single.

Binary mergers unlikely to account for all single low-mass WDs.

Suggests alternative formation channels like winds or substellar interactions.

Abstract

We describe spectroscopic observations of 21 low-mass (<0.45 M_sun) white dwarfs (WDs) from the Palomar-Green Survey obtained over four years. We use both radial velocities and infrared photometry to identify binary systems, and find that the fraction of single, low-mass WDs is <30%. We discuss the potential formation channels for these single stars including binary mergers of lower-mass objects. However, binary mergers are not likely to explain the observed number of single low-mass WDs. Thus additional formation channels, such as enhanced mass loss due to winds or interactions with substellar companions, are likely.