报告题目：Asteroseismology of a d Scuti star HD50844
报 告 人：Yan Li (Yunnan Observatory)
报告时间：2017年3月16日下午2：00
报告地点：蒙民伟科技南楼S727
报告摘要：δ Scuti stars are among the first identified multi-frequency pulsators, and are therefore considered to be important targets of asteroseismology. However, how to identify the spherical harmonic index of an observed pulsation frequency is a long-standing problem for the theoretical modelling, and this area has not made much progress up to now. Using observational data obtained from CoRoT space telescope, we did asteroseismological research for a δ Scuti star HD50844. Based on 40 independent frequencies Balona derived from the light curve, and taking into account of the star's rotational data, we tried to search for frequency splitting of pulsation due to the stellar rotation. We have astonishingly found three kinds of frequency splitting value (2.434μHz, 4.009μHz, and 4.462μHz), and their ratios (0.6:1.0:1.1) perfectly satisfy the asymptotic relation for the rotational splitting of nonradial g-mode pulsation. Finally, we have identifies three sets of l=1 multiplets, seven sets of l=2 multiplets, and three sets of l=3 multiplets. We calculated a large amount of stellar models in an extended parameters space, and compared theoretical pulsation frequencies of each stellar model with frequencies of three identified m=0 modes and a radial fundamental mode identified in the literature through the x2fitting. We have found from the fitting results that only in a very small range of stellar mass and metallicity can we find the best fitting models with the observations. We finally determined the best fitting model to be a post main sequence star, with its mass 1.81M⊙, metallicity Z=0.008, effective temperature 7508K, radius 3.30 R⊙，and luminosity 30.98L⊙. The star is composed of a helium core and a hydrogen-abundant envelope, and the helium core mass is determined to be 0.173 M⊙. This is the first time to determine the size of the helium core for d Scuti stars.
