Context. Subdwarf B pulsators exhibit pressure (p) and/or gravity (g) modes. Their frequency spectra range from very simple, with
few frequencies, to very rich, with more than fifty peaks in some cases. Balloon09 is a hybrid pulsating subdwarf B, showing a large
number of p- and g-modes including a triplet and a quintuplet-like structures which are interpreted as p-mode frequency splittings
due to stellar rotation. Photometric observations undertaken in two subsequent years revealed a change in these rotational splittings
of 0.24 − 0.58 µHz/yr.
Aims. We analyse the possibility of angular momentum interchange between stellar rotation and internal gravity waves as a mechanism
for the observed rotational splitting variations.
Methods. The expected change in the rotational splitting of eigenmodes resulting from this mechanism are computed in the non-
adiabatic linear approximation for a stellar structure model that is representative of the target star. The fact that g-modes are also
observed in Balloon09 makes it a particularly suitable candidate for our study, because the change in the rotational splittings are
proportional to the amplitude squared of the g-modes which, in this case, can be estimated from the observations.
Results. We find that this mechanism is able to predict changes in the splittings that can be of the same order of magnitude as the
observed variations.
Key words. subdwarfs – stars: oscillations – stars: rotation