The origin of single low-mass WDs: another problem that consequential angular momentum loss in CVs might solve

Abstract

Low-mass helium-core white-dwarfs (WDs) with masses below 0.5 Msun are known to be formed in binary star systems but unexpectedly a significant fraction of them seem to be single. On the other hand, in Cataclysmic Variables (CVs) a large number of low-mass WD primary stars is predicted but not observed. We recently showed that the latter problem can be solved if consequential angular momentum loss causes especially CVs with low-mass WDs to merge and form single stars. Here we simulate the population of single WDs resulting from single star evolution and from binary star mergers taking into account these new merging CVs. We show that according to the revised model of CV evolution, merging CVs might be the dominant channel leading to the formation of low-mass single WDs and that the predicted relative numbers are consistent with observations. This can be interpreted as further evidence for the revised model of CV evolution we recently suggested. This model includes consequential angular momentum loss that increases with decreasing WD mass and might not only explain the absence of low-mass WD primaries in CVs but also the existence of single low-mass WDs.

5 pages, 3 figures. Accepted for publication in MNRAS

References in corpus (10)

• White Dwarf Mass Distribution in the SDSS
• Stellar Multiplicity and the IMF: Most Stars Are Single
• Post-common-envelope binaries from SDSS. IX: Constraining the common-envelope efficiency
• The ELM Survey. I. A Complete Sample of Extremely Low Mass White Dwarfs
• The fastest unbound star in our Galaxy ejected by a thermonuclear supernova
• On type Ia supernovae and the formation of single low-mass white dwarfs
• The Future is Now: the Formation of Single Low Mass White Dwarfs in the Solar Neighborhood
• Monte Carlo simulations of post-common-envelope white dwarf + main sequence binaries: The effects of including recombination energy
• White dwarf masses in cataclysmic variables
• The evolution of the self-lensing binary KOI-3278: evidence of extra energy sources during CE evolution

Cited by in corpus (2)

• The binary fraction, separation distribution, and merger rate of white dwarfs from SPY
• MOCCA-SURVEY database I. Accreting white dwarf binary systems in globular clusters -- III. Cataclysmic variables -- Implications of model assumptions