SOME RESULTS OF CCD-PHOTOMETRY OF VARIABLE STARS AT THE ASTRONOMICAL INSTITUTE OF KARAZIN KHARKIV NATIONAL UNIVERSITY

Abstract

We presented photometric observations for the one UV Ceti type and three W Ursae Majoris- type variable stars. The flare of the UV Ceti type star lasted about two hours, and the star changed magnitude to 3.9 within about two minutes. The values of color indices V-R, the rotational periods and the composite lightcurves have been obtained for the EW stars. Using a relation of an absolute magnitude- period obtained by Mateo and Rucinski (2017) and interstellar extinction from the three-dimensional map of Milky Way dust (http://argonaut.skymaps.info) and Green et al. (2019), we have calculated the absolute magnitudes of the EW stars and distances to them. The parallaxes obtained from our data differ from those given in Gaia DR 3, which may be due to insufficient quality calibration of the absolute magnitude-period relation and with the estimations of interstellar extinction.