Measuring Stellar Angular Diameter Through Optical Asteroid Occultation

The resolution of a point source can be limited in the deep sky. Asteroid occultation provided another approach for measuring stellar angular diameter. An asteroid occultation is when an asteroid passes in front of a star. This work is a continuation of W. Benbow et al. (Nature, 2019), which demonstrates the accessibility of angular diameter measurements to imaging atmospheric Cherenkov telescopes (IACTs) through asteroid occultations events. The data used for this project was observed with the IACT array VERITAS (Very Energetic Radiation Imaging Telescope Array System) located near Tucson, Arizona. VERITAS is designed to observe gamma-ray, specialized with a large collecting mirror (>100 m²) and a fast-timing system (500 MHz bandwidth). VERITAS, with different specifications compared to other optical telescopes and optical observation updates, allows us to observe asteroid occultations. Each occultation observed and detected by VERITAS will be fitted to a diffraction pattern to determine the size of the occulted star. Asymmetries between the diffraction patterns of the stellar ingress and egress across the occulting asteroid may provide additional information on the shape of the asteroid. Simulated asteroid occultation data have also been analyzed to test the reliability of the method. The primary star and asteroid presented here are TYC 2924-02100-1 and Egeria respectively. The resulting angular diameter will contribute to the angular diameter catalog from VERITAS to support future studies.