  There are over 100 Be stars that are known to have neutron star companions
but only one such system with a black hole. Previous theoretical work suggests
this is not due to their formation but due to differences in X-ray luminosity.
It has also been proposed that the truncation of the Be star's circumstellar
disc is dependent on the mass of the compact object. Hence, Be star discs in
black hole binaries are smaller. Since accretion onto the compact object from
the Be star's disc is what powers the X-ray luminosity, a smaller disc in black
hole systems leads to a lower luminosity. In this paper, simulations are
performed with a range of eccentricities and compact object mass. The disc's
size and density are shown to be dependent on both quantities. Mass capture
and, in turn, X-ray luminosity are heavily dependent on the size and density of
the disc. Be/black hole binaries are expected to be up to ~10 times fainter
than Be/neutron star binaries when both systems have the same eccentricity and
can be 100 times fainter when comparing systems with different eccentricity.
