The recent detection of both pressure and high-order gravity modes in the
classical B-type pulsator Gamma 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 beta Cephei and slowly pulsating B stars computed using
OP opacity tables, although OPAL calculations may also be compatible with the
observations once the uncertainties in the stellar parameters and the current
limitations of the stability calculations are taken into account. The two known
frequencies f1 = 6.58974 and f2 = 0.68241 c/d are detected in the spectroscopic
time series. A mode identification 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 Gamma Peg and find no evidence for variations that can be
ascribed to orbital motion, contrary to previous claims in the literature.Comment: 28 pages, 16 figure