On Interpreting g-Mode Period Spacings in sdB Stars

Long period B subdwarf (sdB) pulsators, when observed from space with the satellites CoRoT and Kepler, show particularly rich g-mode oscillation spectra with often hundreds of frequencies. In many of these pulsation spectra, regularities in the observed period distributions typical of high order g-modes in chemically homogeneous stars have been reported. This led to a claim that sdB stars could be much less chemically stratified than previously thought. In this paper, we show that such an interpretation is unfounded. We reinvestigate trapping effects on g-modes in sdB stars in view of current observations and show that ”standard” stratified models can also produce nearly quasi-constant period spacings in the low frequency range which are comparable to those observed in the g-mode spectra of these stars.