NEAR-INFRARED PHOTOMETRIC STUDIES OF RZ CASSIOPEIAE

Light curves of the Algol-type binary system, RZ Cassiopeiae, in the n ear-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 pro gram. 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 temper ature 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 at tempted 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 o n the secondary. Another possible reason for the above mentioned effec ts is a gas stream from the lobe-filling secondary to the primary star . The magnitudes and colors of the individual components are derived f rom the observed light curves and the light contributions from the sta rs derived from the light curve analysis. The primary is found to be a n A3 V star as observed by previous investigators. The secondary is cl assified as K0-K4 IV from the derived colors. Seven epochs of primary minima and 3 epochs of secondary minima are obtained from the observat ions. Because of the increased depths of the secondary eclipse in the infrared bands, the moments of minima are calculated with nearly the s ame accuracy as that of the primary minima. All the secondary minima a re found to occur at phase 0.5. None of the observed primary minima ar e flat as found by many observers before at optical wavelengths. The c olors of the system at the minima obtained by us confirm that the syst em is partially eclipsing.