Angular Sizes, Radii, and Effective Temperatures of B-type Stars from Optical Interferometry with the CHARA Array

We present interferometric observations of 25 spectral type-B stars that were made with the Precision Astronomical Visible Observations and the CLassic Interferometry with Multiple Baselines beam combiners at the Center for High Angular Resolution Astronomy Array (CHARA). The observations provide the angular sizes of these stars with an average error of 6%. The stars range in size from 1.09 mas for β Tau down to 0.20 mas for 32 Ori. We collected ultraviolet to infrared spectrophotometry and derived temperatures, angular diameters, and reddening estimates that best fit the spectra, as well as solutions with the angular size fixed by the interferometric measurements. There is generally good agreement between the observed and spectral fit angular diameters, indicating that the fluxes predicted from model atmospheres are reliable. On the other hand, the temperatures derived from angular diameters and fluxes tend to be larger (by ≈4%) than those from published results based on analysis of the line spectrum. This discrepancy may in part be attributed to unexplored atmospheric parameters or the existence of unknown companions. The physical radii of the stars are calculated from the angular diameters and Gaia DR2 parallaxes, and the target stars are placed in the Hertzsprung-Russell diagram for comparison with evolutionary tracks.