Abstract
Light curves of the Algol-type binary system, RZ Cassiopeiae, in the near-IR wavelengths J and K are obtained for the first time. The light curves are analyzed using the Wilson-Devinney model. UBV light curves of RZ Cas obtained by Chambliss are also reanalyzed using the same program. In the J and K bands, the bolometric albedo of the secondary of RZ Cas exhibited values above 0.7, whereas the theoretically expected value for such a star is 0.5. Also, the values of the secondary temperature derived from the J and K light curves are found to be less than that derived from our analysis of the optical light curves as well as from the previous studies in the optical photometric bands. We have attempted to model these effects with a dark spot on the secondary of RZ Cas. The J-band light curve gave a better fit with a cool dark spot on the secondary. Another possible reason for the above mentioned effects is a gas stream from the lobe-filling secondary to the primary star. The magnitudes and colors of the individual components are derived from the observed light curves and the light contributions from the stars derived from the light curve analysis. The primary is found to be an A3 V star as observed by previous investigators. The secondary is classified as K0–K4 IV from the derived colors. Seven epochs of primary minima and 3 epochs of secondary minima are obtained from the observations. Because of the increased depths of the secondary eclipse in the infrared bands, the moments of minima are calculated with nearly the same accuracy as that of the primary minima. All the secondary minima are found to occur at phase 0.5. None of the observed primary minima are flat as found by many observers before at optical wavelengths. The colors of the system at the minima obtained by us confirm that the system is partially eclipsing.