Common envelope (CE) evolution, which is crucial in creating short-period binaries and associated astrophysical events, can be constrained by reverse modelling of such binaries’ formation histories. Through analysis of a sample of well-constrained white dwarf (WD) binaries with low-mass primaries (seven eclipsing double WDs, two non-eclipsing double WDs, one WD-brown dwarf), we estimate the CE energy efficiency αCE needed to unbind the hydrogen envelope. We use grids of He- and CO-core WD models to determine the masses and cooling ages that match each primary WD’s radius and temperature. Assuming gravitational wave-driven orbital decay, we then calculate the associated ranges in post-CE orbital period. By mapping WD models to a grid of red giant progenitor stars, we determine the total envelope binding energies and possible orbital periods at the point CE evolution is initiated, thereby constraining αCE. Assuming He-core WDs with progenitors of 0.9–2.0 M⊙, we find αCE ∼ 0.2–0.4 is consistent with each system we model. Significantly higher values of αCE are required for higher mass progenitors and for CO-core WDs, so these scenarios are deemed unlikely. Our values are mostly consistent with previous studies of post-CE WD binaries, and they suggest a nearly constant and low envelope ejection efficiency for CE events that produce He-core WDs.
- Award ID(s):
- 2009713
- NSF-PAR ID:
- 10426784
- Date Published:
- Journal Name:
- Monthly notices of the Royal Astronomical Society
- Volume:
- 497
- Issue:
- 2
- ISSN:
- 0035-8711
- Page Range / eLocation ID:
- 1895–1903
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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