H alpha emission line spectroscopy in NGC 330 - On the hybrid model for global oscillations in Be star circumstellar disks

We perform an observational test on global oscillations in Be star circumst ellar disks in the metal deficient environment of the SMC. According to the hybrid model of disk oscillations early-type Be stars require an optically thin line force to establish a density wave. The low metallicity in the SM C should therefore diminish or prevent the formation of disk oscillations i n early-type Be stars. We present short wavelength range spectra around H a lpha of 48 Be stars in the young open cluster NGC 330 in the SMC. We find t hat the fraction of early-type Be stars in NGC 330 which host a global disk oscillation does not differ from the known fraction of Galactic field Be s tars. This observational result is in contradiction to the theoretical pred iction. We discuss several interpretations and propose a further observatio nal test.