On the formation of hydrogen-deficient low-mass white dwarfs
Abstract
Context. Two of the possible channels for the formation of low-mass (M⋆ ≲ 0.5 M⊙) hydrogen-deficient white dwarfs are the occurrence of a very-late thermal pulse after the asymptotic giant-branch phase or a late helium-flash onset in an almost stripped core of a red giant star.
Aims: We aim to asses the potential of asteroseismology to distinguish between the hot flasher and the very-late thermal pulse scenarios for the formation of low-mass hydrogen-deficient white dwarfs.
Methods: We computed the evolution of low-mass hydrogen-deficient white dwarfs from the zero-age main sequence in the context of the two evolutionary scenarios. We explore the pulsation properties of the resulting models for effective temperatures characterizing the instability strip of pulsating helium-rich white dwarfs.
Results: We find that there are significant differences in the periods and in the period spacings associated with low radial-order (k ≲ 10) gravity modes for white-dwarf models evolving within the instability strip of the hydrogen-deficient white dwarfs.
Conclusions: The measurement of the period spacings for pulsation modes with periods shorter than ∼500 s may be used to distinguish between the two scenarios. Moreover, period-to-period asteroseismic fits of low-mass pulsating hydrogen-deficient white dwarfs can help to determine their evolutionary history.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- June 2020
- DOI:
- 10.1051/0004-6361/202037743
- arXiv:
- arXiv:2003.13602
- Bibcode:
- 2020A&A...638A..30B
- Keywords:
-
- white dwarfs;
- asteroseismology;
- stars: evolution;
- stars: interiors;
- stars: oscillations;
- stars: low-mass;
- Astrophysics - Solar and Stellar Astrophysics
- E-Print:
- 7 pages, 7 figures. Accepted for publication in A&