Practical Aspects of Calibrating Near-Infrared Interferometer Data: Predicting Stellar Angular Sizes

Reliable prediction of stellar diameters, particularly angular diameters, is a useful and necessary tool for the increasing number of milliarcsecond resolution studies being carried out in the astronomical community. Specifically, the task of calibrating visibility amplitude information from astronomical interferometers often requires the ability to reliably estimate diameters and uncertainties associated with those diameters. The approaches generally used throughout the literature are discussed and compared. Predictions from assumptions of stellar linear size and distance are generally poor, while fitting these objects as blackbody radiators is a better approach, with certain limitations discussed herein. A relatively accurate technique of predicting V = 0 and B = 0 apparent angular sizes is presented for both giant and supergiant stars, and for more evolved sources. This technique uses observed B, V , and K magnitudes to predict angular sizes for giant and supergiant stars to 22–25% for a 99% confidence level result. Application of these techniques towards the task of normalizing visibilities from interferometers is also discussed in detail. Subject headings: Instrumentation: interferometers — stars: fundamental parameters — infrared: stars