Nonradial oscillations of cooling white dwarfs.

Abstract

view Abstract Citations (101) References (23) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Nonradial oscillations of cooling white dwarfs. Osaki, Y. ; Hansen, C. J. Abstract The equations for linear adiabatic nonradial oscillations have been solved for cooling whitedwarf models. Periods and eigenfunctions are obtained for the g2, g1, P', P2 modes of nonradial quadrupole oscillations. Periods of the g1-mode range from 50 to 200 seconds for typical white- dwarf stars with M = 0.4 1.0M0 and L = 10-4L0 10-2L0. It is shown that there exist period-luminosity relations for g-modes along the cooling white-dwarf sequence. The damping of nonradial oscillations due to radiative heat leakage, neutrino losses, and gravitational radiation is studied in the quasi-adiabatic approximation, and all models are found to be pulsationally stable. It is found that the emission of gravitational waves is the most efficient mechanism for the damping of f- and p-modes while radiative heat leakage is the most efficient for g-modes. Damping times range from a few tens of years to about 10 years-time scales much shorter than Kelvin or cooling times for white dwarfs. Results are compared with observations of ultrashort-period variables. It is suggested that light variations of HL Tau 76 (P = 747 s) and G44-32 (F = 600 s) may be associated with nonradial g1 oscillations of white dwarfs with convective envelopes. The importance of gravitational radiation from nova outbursts is also discussed. Subject headings: gravitation - interiors, stellar - pulsation - white dwarf stars Publication: The Astrophysical Journal Pub Date: October 1973 DOI: 10.1086/152415 Bibcode: 1973ApJ...185..277O full text sources ADS | data products SIMBAD (7)