Observation of the Grazing Occultation of the TYC 1280-832-1 Star by the Asteroid (486) Cremona

Abstract

A description of the method for observing the occultation of stars by asteroids at the astronomical complex for observing the occultation of stars by Solar System bodies is given. The complex uses an Apogee Alta U47 CCD camera as a light detector, which operates in a time delay and integration (TDI) mode. Results of the study of the occultation phenomenon of the TYC 1280-832-1 star by the asteroid (486) Cremona on December 5, 2019, which was obtained using this complex, are described. The decrease in brightness on the photometric curve of the TYC 1280-832-1 star at the time moment that corresponds to the ephemeris occultation time within the limits of measurement errors is observed. The decrease in brightness goes beyond the 2σ error, which was determined along the entire length of the star’s track. This value exceeds the possible level of photometry errors of the star track. A possible explanation for this effect of light attenuation by a short-term grazing occultation, when the star does not completely close, is analyzed. The theoretical model of the formation of a photometric curve for this observation method taking into account diffraction phenomena and parameters of stars in the field of view has been developed to verify this statement. We showed that this can explain the magnitude and time interval of brightness attenuation. The obtained estimates of the occultation parameters for this event are as follows: the minimum fraction of the uncovered area is 48 ± 15%, which corresponds to the position of the edge of the asteroid from the star center in fractions of its radius from –0.17 to +0.21.