Radial velocities of low-mass white dwarfs

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.