Abstract:
The recent detection of both pressure and high-order gravity modes in the clas-
sical B-type pulsator γ Pegasi offers promising prospects for probing its internal
structure through seismic studies. To aid further modelling of this star, we
present the results of a detailed NLTE abundance analysis based on a large
number of time-resolved, high-quality spectra. A chemical composition typical
of nearby B-type stars is found. The hybrid nature of this star is consistent with
its location in the overlapping region of the instability strips for β Cephei and
slowly pulsating B stars computed using OP opacity tables, although OPAL cal-
culations may also be compatible with the observations once the uncertainties
in the stellar parameters and the current limitations of the stability calcula-
tions are taken into account. The two known frequencies f1 = 6.58974 and
f2 = 0.68241 d−1 are detected in the spectroscopic time series. A mode iden-
tification is attempted for the low-frequency signal, which can be associated to
a high-order g-mode. Finally, we re-assess the binary status of γ Peg and find
no evidence for variations that can be ascribed to orbital motion, contrary to
previous claims in the literature.
