The hybrid B-type pulsator $\gamma$ Pegasi: mode identification and complex seismic modelling

Abstract

We present interpretation of the oscillation spectrum of the early B-type star $\gamma$ Pegasi, in which both low order p/g and high-order g-modes are observed. Using amplitudes and phases of the photometric and radial velocity variations, we identify/constrain the mode degree, $\ell$, for all 14 detected frequencies. Seismic models fitting two pulsational frequencies corresponding to the modes $\ell=0$, p$_1$ and $\ell=1$, g$_1$ were constructed. This set of models contains those which reproduce also the empirical values of the complex nonadiabatic parameter $f$ associated to these two mode frequencies. Unfortunately, there are no models reproducing the values of $f$ for both frequencies simultaneously, regardless of model atmospheres, opacity data, chemical mixture as well as opacity enhancement in the $Z-$ and Deep Opacity Bumps. Most probably, some modifications of the opacities in stellar interiors are still required.