Double white dwarf (WD) binaries are increasingly being discovered at short orbital periods where strong tidal effects and significant tidal heating signatures may occur. We assume that the tidal potential of the companion excites outgoing gravity waves within the WD primary, the dissipation of which leads to an increase in the WD’s surface temperature. We compute the excitation and dissipation of the waves in cooling WD models in evolving
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.
more » « less- Award ID(s):
- 2205974
- NSF-PAR ID:
- 10474506
- Publisher / Repository:
- Oxford University Press
- Date Published:
- Journal Name:
- Monthly Notices of the Royal Astronomical Society
- Volume:
- 518
- Issue:
- 3
- ISSN:
- 0035-8711
- Format(s):
- Medium: X Size: p. 3966-3984
- Size(s):
- ["p. 3966-3984"]
- Sponsoring Org:
- National Science Foundation
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