PULSATING PRE-MAIN SEQUENCE STARS AS POSSIBLE EDDINGTON TARGETS

摘要

PMS stars lie between the birthline and the zero-age main sequence (ZAMS) in the Hertzsprung-Russell (HR) diagram. They show photometric and spectroscopic variability on time scales of minutes to years, indicating that photospheric activity begins in the earliest phases of stellar evolution. The fact that they move across the instability region during their evolution to the main sequence suggests that at least part of their activity is due to stellar pulsations. δ Scuti-like PMS stars are ideal targets for the Eddington mission. First, their location in open clusters provides the simultaneous observation of numerous objects as a photometric reference. Second, the PMS variables lie in a magnitude range between V = 8 and V = 15, which meets the requirements of the mission. Third, the analysis of these stars by means of asteroseis-mological methods provides the unique chance to distinguish between young and evolved stars and hence leads to a better fundamental understanding of stellar structure and evolution.