Comparing the observational instability regions for pulsating pre-main-sequence and classical δ Scuti stars

A comparison of the hot and cool boundaries of the classical instability strip with observations has been an important test for stellar structure and evolution models of post- and main-sequence stars. Over the last few years, the number of pulsating pre-main-sequence (PMS) stars has increased significantly: 36 PMS pulsators and candidates are known as of 2007 June. This number allows to investigate the location of the empirical PMS instability region and to compare its boundaries to those of the classical (post- and main-sequence) instability strip. Due to the structural differences of PMS and (post-)main-sequence stars, the frequency spacings for nonradial modes will be measurably different, thus challenging asteroseismology as a diagnostic tool.