QUIESCENT NUCLEAR BURNING IN LOW-METALLICITY WHITE DWARFS
- Facultad de Ciencias Astronómicas y Geofísicas, Universidad Nacional de La Plata, Paseo del Bosque s/n, 1900 La Plata (Argentina)
- Departament de Física Aplicada, Universitat Politècnica de Catalunya, c/Esteve Terrades 5, E-08860 Castelldefels (Spain)
We discuss the impact of residual nuclear burning in the cooling sequences of hydrogen-rich (DA) white dwarfs with very low metallicity progenitors (Z = 0.0001). These cooling sequences are appropriate for the study of very old stellar populations. The results presented here are the product of self-consistent, fully evolutionary calculations. Specifically, we follow the evolution of white dwarf progenitors from the zero-age main sequence through all the evolutionary phases, namely the core hydrogen-burning phase, the helium-burning phase, and the thermally pulsing asymptotic giant branch phase to the white dwarf stage. This is done for the most relevant range of main-sequence masses, covering the most usual interval of white dwarf masses—from 0.53 M {sub ☉} to 0.83 M {sub ☉}. Due to the low metallicity of the progenitor stars, white dwarfs are born with thicker hydrogen envelopes, leading to more intense hydrogen burning shells as compared with their solar metallicity counterparts. We study the phase in which nuclear reactions are still important and find that nuclear energy sources play a key role during long periods of time, considerably increasing the cooling times from those predicted by standard white dwarf models. In particular, we find that for this metallicity and for white dwarf masses smaller than about 0.6 M {sub ☉}, nuclear reactions are the main contributor to the stellar luminosity for luminosities as low as log (L/L {sub ☉}) ≅ –3.2. This, in turn, should have a noticeable impact in the white dwarf luminosity function of low-metallicity stellar populations.
- OSTI ID:
- 22215436
- Journal Information:
- Astrophysical Journal Letters, Vol. 775, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 2041-8205
- Country of Publication:
- United States
- Language:
- English
Similar Records
NEW COOLING SEQUENCES FOR OLD WHITE DWARFS
The core mass growth and stellar lifetime of thermally pulsing asymptotic giant branch stars