Research Division Seminar
Single-photon gig in Betelgueuse's occultation

Abstract

We present our results from observing the occultation of Betelgeuse by asteroid (319) Leona on December 12,2023, using a cutting-edge 64 x 64 pixel Single-Photon Avalanche Diode (SPAD) array mounted on a 10-inch telescope at the AstroCamp Observatory in Nerpio, Southeast of Spain, located just a few kilometers from the center of the occultation shadow path. This study marks a remarkable advancement in applying SPAD technology in astronomy. The SPAD array's asynchronous readout capacity and photon-counting timestamp mode enabled us to achieve a temporal resolution of I microsecond in our light curve observations of Betelgeuse. The data analysis addresses challenges inherent to SPAD arrays, such as optical cross-talk and afterpulses, which cause the photon statistics to deviate from a Poisson distribution. By adopting a generalized negative binomial distribution (NBD) for photon statistics, we accurately describe the observational data. This approach yields an optical cross-talk estimation of l.OlVo in our SPAD array and confirmed a negligible impact of spurious detected events from afterpulses. The meticulous statistical examination of photon data underscores our SPAD-array's exceptional performance in conducting precise astronomical observations. The observations reveal a major decrease in Betelgeuse's intensity by 77.78Vo at the occultation's peak, allowing the measurement of Betelgeuse's angular diameter to be 57.26 mas in the SDSS g-band. This measurement was obtained by employing a simplified occultation model and considering the known properties of Leona. This work not only demonstrates the potential of SPAD technology in astronomy but also sets a new standard for observations of transient celestial events, offering a precious public dataset for the astronomical community.