Towards Asteroseismology of the Non-radial Pulsating Sdb Star Pg 1605+072

The recently discovered new class of sdB pulsators (sdBV) offers a powerful possibility for the investigation of their interior and thus their evolutionary history. The first step towards applying asteroseismologic tools is the identification of pulsation modes. The best target for such an investigation is PG 1605+072 because of its outstanding properties among the sdBVs: it is the brightest object (B = 13 mag), it has the longest periods (∼ 500 s) and the largest variations (0.2 mag in the optical) as well as the richest pulsation spectrum with more than 50 modes (see Kilkenny et al. 1999). The rather rapid rotation (v sin i = 39 km/s, Heber et al. 1999) complicates the interpretation of the pulsation spectrum due to non-linear mode splitting. We want to accomplish the mode identification by measuring both the light and the radial velocity curve for PG 1605+072. The analysis of equivalent width changes of the Balmer lines and of line profile variations (as a future task in preparation) will support the aim of the project. Moreover, we want to determine light/velocity amplitude ratios and search for a wavelength dependence of photometric amplitudes which gives us information on limb darkening effects. The interpretation of these measurements require sophisticated models. Phase dependent synthetic spectra will be calculated with a code developed by Falter (2001). As a prerequisite for these models the time dependent sur