We combine all the reliably-measured eigenperiods for hot, short-period ZZ Ceti stars onto one diagram and show that it has the features expected from evol0utionaryand pulsation theory. To make a more detailed comparison with theory we concentrate on a subset of 16 stars for which rotational splitting or other evidence gives clues to the spherical harmonic index (ℓ) of the modes. The suspected ℓ = 1 periods in this subset of stars form a pattern of consecutive radial overtones that allow us to conduct ensemble seismology using published theoretical model grids. We find that the best-matching models have hydrogen layer masses most consistent with the canonically thick limit calculated from nuclear burning. We also find that the evolutionary models with masses and temperatures from spectroscopic fits cannot correctly reproduce the periods of the k = 1 to 4 mode groups in these stars, and speculate that the mass of the helium layer in the models is too large.
20th European White Dwarf Workshop
- Pub Date:
- March 2017
- Astrophysics - Solar and Stellar Astrophysics
- 6 pages, 4 figures. To appear in the ASP Conference Series proceedings of "20th European Workshop Workshop on White Dwarfs" held at the University of Warwick, UK on July 25-29th, 2016