Nonadiabatic Pulsations in Pre-Main Sequence Delta Scuti Stars
Matthew R. Templeton, Sarbani Basu
Astronomy Department, Yale University,
PO Box 208101, New Haven, CT 06520-8101, USA
We computed a set of pre-main sequence models using the YREC evolution code
to study delta Scuti pulsations of PMS stars, focusing on their non-adiabatic
properties and the region of instability in the H-R diagram. The properties
of the radial ( = 0) modes on the early pre-main sequence are very
similar to those on the late post-main sequence, with slightly shorter periods
corresponding to smaller radii. The period ratio 1/ 0
lies at low values of 0.5 near the base of the Hayashi track, but
rapidly rises to values near 0.77 typical of delta Scuti stars once the stellar
models move closer to the ZAMS. We find unstable models ( E/E>0)
on the pre-main sequence for all models between 1.5 and 4.0 solar
masses, though at the high-mass end, the fundamental blue edge is reached very
early in the pre-main sequence lifetime. The slope of the pre-main sequence
blue edge appears to overlap the edge for the main- and post-main sequence
stars. We also tested models for V346 Ori similar to those described in
Pinhiero et al. (IAU Colloq. 185, 2001), and find that while V346 Ori almost
certainly lies near the ZAMS, it is uncertain whether it is a pre-main sequence star.
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Last changed: 2002/Jun/19
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