Asteroseismology of the DOV star PG 1159 - 035 with the Whole Earth Telescope

We report the results from 264.1 hr of nearly continuous time-series photometry on the pulsating pre-white dwarf star (DOV) PG 1159-035. The high-resolution power spectrum of this data set is dominated by power in the range from roughly 1000 to 2600 μHz (1000 s to 385 s periods). This power is completely resolved into 125 individual frequencies; we have identified 101 of them with specific, quantized pulsation modes, and the rest are completely consistent with such modal assignment. The luminosity variations are therefore certainly the result of g-mode pulsations. Although the amplitudes of some of the peaks exhibit significant variations on time scales of a year or so, the underlying frequency structure of the pulsations is stable over much longer intervals. With the help of existing linear theory we use these identifications to determine, or strongly constrain, many of the fundamental physical parameters describing this star. We find its mass to be 0.586 M<SUB>⊙</SUB>, its rotation period 1.38 days, its magnetic field less than 6000 G, its pulsation and rotation axes to be aligned, and its outer layers to be compositionally stratified. With straightforward extensions of existing theory it may be possible to determine uniquely from this data set all of the parameters necessary to construct a quantitative model of its interior. These observations also reveal several interesting phenomena that challenge the current theory of nonradial pulsations, and may require substantial new developments to describe them.