Evolutionary Models for the Remnant of the Merger of Two Carbon-Oxygen Core White Dwarfs
Abstract
We construct evolutionary models of the remnant of the merger of two carbon-oxygen (CO) core white dwarfs (WDs). With total masses in the range 1-2 M⊙, these remnants may either leave behind a single massive WD or undergo a merger-induced collapse to a neutron star (NS). On the way to their final fate, these objects generally experience a ˜10 kyr luminous giant phase, which may be extended if sufficient helium remains to set up a stable shell-burning configuration. The uncertain, but likely significant, mass-loss rate during this phase influences the final remnant mass and fate (WD or NS). We find that the initial CO core composition of the WD is converted to oxygen-neon (ONe) in remnants with final masses ≳1.05 M⊙. This implies that the CO core/ONe core transition in single WDs formed via mergers occurs at a similar mass as in WDs descended from single stars and thus that WD-WD mergers do not naturally provide a route to producing ultramassive CO-core WDs. As the remnant contracts toward a compact configuration, it experiences a "bottleneck" that sets the characteristic total angular momentum that can be retained. This limit predicts that single WDs formed from WD-WD mergers have rotational periods of ≍10-20 minutes on the WD cooling track. Similarly, it predicts remnants that collapse can form NSs with rotational periods ˜10 ms.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- January 2021
- DOI:
- 10.3847/1538-4357/abc87e
- arXiv:
- arXiv:2011.03546
- Bibcode:
- 2021ApJ...906...53S
- Keywords:
-
- White dwarf stars;
- Stellar mergers;
- Supernovae;
- Neutron stars;
- 1799;
- 2157;
- 1668;
- 1108;
- Astrophysics - Solar and Stellar Astrophysics;
- Astrophysics - High Energy Astrophysical Phenomena
- E-Print:
- 18 pages, 16 figures