  In this paper we study the effect of the quadrupole-term in the gravitational
potential of a rotationally deformed central Be star on one armed density waves
in the circumstellar disc.
  The aim is to explain the observed long-term violet over red (V/R) intensity
variations of the double peaked Balmer emission-lines, not only in cool Be star
systems, but also in the hot systems like gamma Cas. We have carried out
semi-analytic and numerical studies of low-frequency one armed global
oscillations in near Keplerian discs around Be stars. In these we have
investigated surface density profiles for the circumstellar disc which have
inner narrow low surface density or gap regions, just interior to global maxima
close to the rapidly rotating star, as well as the mode inner boundary
conditions. Our results indicate that it is not necessary to invoke extra
forces such as caused by line absorption from the stellar flux in order to
explain the long-term V/R variations in the discs around massive Be stars. When
there exists a narrow gap between the star and its circumstellar disc, with the
result that the radial velocity perturbation is non-zero at the inner disc
boundary, we find oscillation (and V/R) periods in the observed range for
plausible magnitudes for the rotational quadrupole term.
