Stellar astronomy:

Stellar pulsation and Asteroseismology

New class of objects:

PMS and post-MS pulsating stars in the Delta Scuti region, M=1.8MO

Observations:

;

Figure 1: At the center, image of the star pre-main-sequence HD 104237, of magnitude mV=6.6 (the other brighter star is HD 104174, a B9V star of magnitude 4.9.). HD 104237 is a variable Herbig star, for which oscillations have been detected photometrically (by Kurtz & Müller 1999) and spectroscopically (by Donati et al 1997). It is also the only pre-main-sequence star where a magnetic field has been detected directly. It is a tight binary, with a companion of T Tauri type.

Theory:

HR track for a star of 1.8MO (CESAM & HENYEY). Also is shown the instability strip red and blue borders. ;

Pulsational diagram for a star of 1.8MO;

Brunt-Vaisala frequencies for different pms evolutive phases of a 1.8MO star;

compared with Brunt-Vaisala frequencies for different post-ms evolutive phases of a 1.8MO star

;

Reference:
"Comparative seismology of pre- and main sequence stars in the instability strip"
Marian Suran, Marie-Jo Goupil, Annie Baglin, Yveline Lebreton, Claude Catala: 2001 Astronomy and Astrophysics in press
astro-ph/0104319.