Comparative seismology of pre- and main sequence stars in the instability strip

¹ Astronomical Institute of Romanian Academy
² DASGAL, UMR CNRS 8633, Observatoire de Paris-Meudon, France
³ DESPA, UMR CNRS 8632, Observatoire de Paris-Meudon, France
⁴ LAT, UMR CNRS 5572, Observatoire de Midi-Pyrénées, France

Corresponding author: M. Goupil, goupil@obspm.fr

Received: 22 January 2001
Accepted: 30 March 2001

Abstract

Pulsational properties of 1.8 stellar models covering the latest stages of contraction toward the main sequence up to early hydrogen burning phases are investigated by means of linear nonadiabatic analyses. Results confirm that pre-main sequence stars (pms) which cross the classical instability strip on their way toward the main sequence are pulsationally unstable with respect to the classical opacity mechanisms. For both pms and main sequence types of models in the lower part of the instability strip, the unstable frequency range is found to be roughly the same. Some non-radial unstable modes are very sensitive to the deep internal structure of the star. It is shown that discrimination between pms and main sequence stages is possible using differences in their oscillation frequency distributions in the low frequency range.