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Issue A&A Volume 374, Number 1, July IV 2001 Page(s) 116 - 131 Section Formation, structure and evolution of stars DOI 10.1051/0004-6361:20010529

A&A 374, 116-131 (2001)
DOI: 10.1051/0004-6361:20010529

Nonlinear effects in time-resolved spectra of DAVs

J. Ising and D. Koester

Institut für Theoretische Physik und Astrophysik, Universität Kiel, 24098 Kiel, Germany
    e-mail: koester@astrophysik.uni-kiel.de

(Received 26 June 2000 / Accepted 2 April 2001)

Abstract
Numerical simulations of light curves of variable DA white dwarfs (ZZ Ceti stars) predict flux amplitudes with surface distributions different from the spherical harmonics of the pulsation mode in deeper layers. In contrast to the results of the perturbation analysis by Gold reich and Wu, this is also true for the fundamental period of the flux variation. As a consequence, normalized amplitude spectra depend not only on the mode number l but also on pulsation amplitude and inclination. Another new result is that with increasing amplitude of the pressure variation below the convection zone, the flux variation at the surface goes through a maximum and then decreases again.

Key words: stars: white dwarfs -- stars: atmospheres -- stars: interiors -- convection -- stars: variable: general

Offprint request: J. Ising, ising@astrophysik.uni-kiel.de

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