Observation of the grazing occultation of the star TYC 1280-832-1 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 Soiar system bodies is given. The complex uses an Apogee Alta U47 CCD camera as a light deiector, which operates in a time delay and integration (TDI) mode. Results of the study of the ocultation phenomenon of the stars TYC 1280-832-1 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 star TYC 1280-832-1, at the moment of time that corresponds within the error with the ephemeris occultation time 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 posiible explanation for this effect of light attenuation through 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 veri fy this statement. It is shown that this can explain the magnitude and time of bright attenuation. The obtained estimates of the occultation parameiers for this event: the minimum fraction of the uncovered area is 48 ± 15%, which corresponds to the position of the edge of the asteroid from the center of the star in fractions of its radius from -0.17 to +0.21.