Comparing the observational instability regions for pulsating pre-main sequence and classical $\delta$ Scuti stars

TL;DR

This paper compares the observed instability regions of pulsating pre-main sequence stars with classical δ Scuti stars, highlighting differences in their boundaries and the implications for asteroseismology.

Contribution

It provides the first empirical comparison of the instability regions for PMS and classical δ Scuti stars, based on an increased sample of known pulsators.

Findings

Empirical PMS instability region boundaries are identified.

Structural differences lead to distinct frequency spacings in pulsations.

Challenges to asteroseismology diagnostics are discussed.

Abstract

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 June 2007. 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.