Fundamental Properties of Three Metal-Poor Stars with Optical/NIR Interferometry

Angular diameters of three metal-poor and one solar metallicity star—HD 184499, HD 22879, and HD 76932 and HD 108510—were measured using the CHARA Array interferometer. Angular diameters θ_LD = 0.403 ± 0.004, 0.397 ± 0.006, 0.570 ± 0.005, and 0.360 ± 0.006 mas were found for HD 184499, HD 22879, HD 76932, and HD 108510, respectively. Using these diameters combined with Hipparcos parallaxes and literature values for bolometric flux, linear radii R = 1.38 ± 0.02, 1.09 ± 0.02, 1.29 ± 0.01, and 1.16 ± 0.03 R_☉; effective temperatures T_eff = 5824 ± 47, 5856 ± 50, 5913 ± 47, and 5950 ± 84 K; and luminosities L = 1.97 ± 0.07, 1.26 ± 0.04, 1.82 ± 0.05, and 1.50 ± 0.09 L_☉ were calculated. Given these values along with literature values for [Fe/H], the Python package Kīauhōkū was used to compute an age and mass for each star from four stellar model grids. For the metal-poor stars, the resulting ages were higher than literature values and the masses lower. For the HD 108510, the resulting ages were higher than literature values while the masses agreed. To investigate the discrepancies in age, all four stars were fitted to DSEP isochrones, accounting for alpha-enhancement in the three metal-poor stars. The resulting fits indicated significantly lower ages than those computed by the model grids for the metal-poor stars and an age for HD 108510 which agreed with the model grids.