LONG-TERM PHOTOMETRIC AND SPECTROSCOPIC OBSERVATIONS OF THE NEAR-CONTACT BINARY KR CYGNI

We present the multi-color, five-year light curves and the radial velocities of the near-contact binary system KR Cyg. We derived the masses of the components as 2.88 +/- 0.20 M-circle dot and 1.26 +/- 0.07 M-circle dot and the radii as 2.59 +/- 0.06 R-circle dot and 1.80 +/- 0.04 R-circle dot. We also searched for the empirical determination of albedo and effective temperature of the cooler, less massive star of KR Cyg, and of two similar near contact binaries AK CMi, and DO Cas. The residuals between the observed and computed fluxes are attributed to the effect of mutual illumination which heats the surface layers of the illuminated star and does vary not only its bolometric albedo but also its limb-darkening coefficient and gravity-brightening exponent. The effective albedos are generally smaller than that expected from an envelope of convective star. These results are preliminary and speculative.