Talk abstract details

$\gamma$ Pegasi is one of a few early B-type pulsators exhibiting simultaneously
low order pressure/mixed modes, typical for $\beta$ Cep variables, and high order gravity modes,
typical for SPB stars. The analysis of MOST observations, supported by ground based photometry
and spectroscopy, revealed 8 frequencies typical for the $\beta$ Cep stars and 6 peaks
in the SPB frequency domain (Handler et al. 2009, ApJ 698, L56, Handler, 2009, MNRAS 398, 1339).
Such stars, called hybrid pulsators, are of special interest for asteroseismic studies
because of a wide frequency range and very different character of p and g modes.

In this talk, we present mode identification for all 14 frequencies and results
of complex seismic modelling of $\gamma$ Pegasi. This modelling consists in parallel
fitting of pulsational frequencies and corresponding values of the complex, nonadiabatic parameter $f$,
defined by the radiative flux variation at the photosphere level (Daszynska-Daszkiewicz \& Walczak 2009, MNRAS 398, 1961).
The concordance of the empirical and theoretical values of $f$ obtained both for low order p and high order g modes
is of special importance because a dependence of the $f$-parameter on the mode frequency and degree, $\ell$,
is very different for these two types of modes.
Complex asteroseismology of B-type hybrid pulsators provides a more plausible test of stellar parameters,
atmospheres and opacities.