This week's first colloquium will be held by Dr. Kathryn Gordon of Agnes Scott College. Dr. Gordon will be giving a talk on "Fundamental Properties of O and B Stars." See this link for access to the zoom meeting. All are welcome to join and learn from this talk!
Abstract: We present interferometric observations of six O-type stars and 25 B-type 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 (CHARA) Array. The stellar angular diameters range from 1.09 mas for β Tau down to 0.11 mas for 10 Lac, the smallest star yet resolved with the CHARA Array. The rotational oblateness of the rapidly rotating star ζ Oph is directly measured for the first time. We assembled ultraviolet to infrared flux measurements for these stars, and then derived angular diameters and reddening estimates using model atmospheres and an effective temperature set by published results from analysis of the line spectrum. The model-based angular diameters are in good agreement with those observed. We also present estimates for the effective temperatures of these stars, derived by setting the interferometric angular size and fitting the spectrophotometry. For the B-type stars 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. 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. I will also provide a brief overview of the interferometric technique.