ASTEROSEISMOLOGY OF HYBRID PULSATORS MADE POSSIBLE: SIMULTANEOUS MOST SPACE PHOTOMETRY AND GROUND-BASED SPECTROSCOPY OF γ PEG

We have acquired simultaneous high-precision space photometry and radial velocities of the bright hybrid beta Cep/Slowly Pulsating B pulsator gamma Peg. Frequency analyses reveal the presence of six gravity (g) modes of high radial order together with eight low-order beta Cep oscillations in both data sets. Mode identification shows that all pulsations have spherical degrees l = 0-2. An 8.5 M(circle dot) model reproduces the observed pulsation frequencies; all theoretically predicted modes in the beta Cep domain are detected. We suggest, contrary to previous authors, that gamma Peg is a single star; the claimed orbital variations are due to g-mode pulsation. gamma Peg is the first hybrid pulsator for which a sufficiently large number of high-order g modes and low-order pressure (p) and mixed modes have been detected and identified to be usable for in-depth seismic modeling.