Type Ia Supernovae and High-Velocity White Dwarfs

I examine the hypothesis that many of the high-velocity white dwarfs observed by Oppenheimer et al. are the remnants of donor stars from binaries that produced Type Ia supernovae (SNe Ia) via the "single degenerate" channel. If this channel is a significant contributor to the Galactic SN Ia rate, then the local density of such remnants with V- > 100 km s-1 could be as high as 2 × 10-4 pc-3, comparable to the densities found by Oppenheimer et al. This white dwarf population differs from others in that it is composed exclusively of single stars. It is also drawn from the thin disk and consequently contains more young stars than the older kinematically hot white dwarf populations. Thus, the determination of the binary fraction among high-velocity white dwarfs can distinguish this population from kinematically similar populations, such as the thick-disk white dwarfs.