  The subdwarf B (sdB) star V391 Peg oscillates in short-period p modes and
long-period g modes, making it one of the three known hybrids among sdBs. As a
by-product of the effort to measure secular period changes in the p modes due
to evolutionary effects on a time scale of almost a decade, the O-C diagram has
revealed an additional sinusoidal component attributed to a periodic shift in
the light travel time caused by a planetary-mass companion around the sdB star
in a 3.2 yr orbit. In order to derive the mass of the companion object, it is
necessary to determine the orbital inclination. One promising possibility to do
this is to use the stellar inclination as a primer for the orbital orientation.
The stellar inclination can refer to the rotational or the pulsational axis,
which are assumed to be aligned, and can in turn then be derived by combining
measurements of v_(rot) and v_(rot)sin i. The former is in principle accessible
through rotational splitting in the photometric frequency spectrum (which has
however not been found for V391 Peg yet), while the projected rotational
velocity can be measured from the rotational broadening of spectral lines. The
latter must be deconvolved from the additional pulsational broadening caused by
the surface radial velocity variation in high S/N phase averaged spectra. This
work gives limits on pulsational radial velocities from a series of phase
resolved spectra. Phase averaged and phase resolved high resolution echelle
spectra were obtained in May and September 2007 with the 9m-class Hobby-Eberly
Telescope (HET), and one phase averaged spectrum in May 2008 with the 10m-Keck
1 telescope.
