ON SOME STARS PROBABLY HAVING EXTENDED ATMOSPHERES OR GAS-DUST SHELLS, OR CIRCUMSTELLAR DISK-LIKE STRUCTURES, ACCORDING TO THE RESULTS OF HIGH-SPEED PHOTOMETRY OF THEIR LUNAR OCCULTATIONS

Abstract

When the edge of the dark part of the lunar disk covers (occults) one or another star, at the movement of the Moon relatively stars in the sky, a diraction eects arise, and as a result one can record a diraction curve of stellar occultation. A typical duration of passing of the rst Fresnel zone over line of sight of the observer for the light source with a very small angular diameter (of the order of a few milliarcseconds (mas)) is of the order of 20 milliseconds (ms), therefore for a sufficiently detailed registration of changes of the light ux in the diraction pattern it is necessary to record them with a time resolution of the order of 1 ms. For that one should have some modern photometric recorder which allows us to record light ux from the investigated star with the mentioned time resolution. If the diraction curve of the lunar occultation of a star is recorded then it is possible to do it's analysis in order to distinguish it from the diraction curve corresponding to the occultation of a point-like source, and thus to determine directly the angular size of the star under study. During more than 35 years a several tens of occultation diraction curves of various stars have been recorded with a time resolution of 1 ms in the Observatories of Sternberg Astronomical Institute of M.V.Lomonosov Moscow State University. When processing the data obtained the angular sizes of some stars have been determined directly. Among the stars studied by the method described, the author discovered a number of objects that, in all probability, have a complex structure and include either an extended stellar atmosphere, or a gas-dust envelope, or a circumstellar disk-like structure. Some examples of such results are presented.