Theoretical seismic properties of pre-main sequence gamma Doradus pulsators

TL;DR

This paper theoretically investigates the seismic properties of pre-main sequence gamma Doradus stars, comparing them with main sequence counterparts to identify observational signatures of their evolutionary phase.

Contribution

It provides the first theoretical instability strip for PMS gamma Dor stars and highlights differences in mode frequency domains and period spacing patterns.

Findings

PMS gamma Dor stars have a larger unstable mode frequency domain than MS stars.

The instability strip for PMS stars overlaps with that of MS stars in temperature.

Period spacing patterns differ between PMS and MS stars, aiding evolutionary phase determination.

Abstract

Context. gamma Doradus (gamma Dor) are late A and F-type stars pulsating with high order gravity modes (g-modes). The existence of different evolutionary phases crossing the gamma Dor instability strip raises the question of the existence of pre-main sequence (PMS) gamma Dor stars. Aims. We intend to study the differences between the asteroseismic behaviour of PMS and main sequence (MS) gamma Dor pulsators as it is predicted by the current theory of stellar evolution and stability. Methods. We explore the adiabatic and non-adiabatic properties of high order g-modes in a grid of PMS and MS models covering the mass range 1.2 Msun < Mstar < 2.5 Msun. Results. We derive the theoretical instability strip (IS) for the PMS gamma Dor pulsators. This IS covers the same effective temperature range as the MS gamma Dor one. Nevertheless, the frequency domain of unstable modes in PMS models with a fully radiative core is larger than in MS models, even if they present the same number of unstable modes. Moreover, the differences between MS and PMS internal structures are reflected on the average values of the period spacing as well as on the dependence of the period spacing on the radial order of the modes, opening the window to the determination of the evolutionary phase of gamma Dor stars from their pulsation spectra.