  We report on luminescent centers contained in a few-layer-thick hexagonal
boron nitride (h-BN) film grown on Ni by molecular beam epitaxy. After transfer
to a SiO$_2$/Si substrate, sharp lines are observed in photo- and
cathodoluminescence spectra in both the ultraviolet and the visible range.
Spatially resolved measurements reveal that the luminescent centers responsible
for these lines are localized within microscopic multi-layer islands that form
at the nucleation centers of the h-BN film. The comparison of their energy,
polarization and phonon replica emission with previous theoretical predictions
suggest that the N$_\mathrm{B}$V$_\mathrm{N}$ anti-site could be one of the
light emitters present in our sample. Moreover, we have also observed evidences
of other kinds of centers that could be associated to defects containing carbon
or oxygen. The characterized luminescent defects could have potential
applications as quantum light sources.
