  We present possible explanations of pulsations in early B-type main sequence
stars which arise purely from the excitation of gravity modes. There are three
stars with this type of oscillations detected from the BRITE light curves:
$\kappa$ Cen, a Car, $\kappa$ Vel. We show that by changing metallicity or the
opacity profile it is possible in some models to dump pressure modes keeping
gravity modes unstable. Other possible scenario involves pulsations of a lower
mass companion.
