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

TL;DR

This study analyzes the oscillation spectrum of the B-type star $ extgamma$ Pegasi, identifying pulsation modes and constructing seismic models, but finds current models cannot fully explain the observed complex nonadiabatic parameters, indicating a need for improved stellar opacities.

Contribution

It provides detailed mode identification and seismic modeling of $ extgamma$ Pegasi, highlighting limitations in current models and suggesting modifications in stellar interior opacities are necessary.

Findings

Identified mode degrees for all 14 detected frequencies.

Constructed seismic models fitting two key pulsation frequencies.

Current models cannot reproduce the complex nonadiabatic parameter $f$ for both frequencies.

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.