Photometric studies of close binary systems

Abstract

Two eclipsing binary stars of the Algol type, RZ Cassiopeiae and R Canis Majoris, are observed in the near IR photometric bands J and K and the light curves are analysed using the Wilson - Devinney light curve synthesis program. Existing light curves of these systems in the optical bands are also analysed with the same program. In the case of RZ Cas, the J & K band light curves gave higher values of bolometric albedo of the secondary star, compared to what is expected theoretically. Also the near IR light curves yielded lower values of derived values of the temperature of the secondary star T2. These two factors are considered as the indication of the presence of a dark spot on the back side of the secondary star and the values of the spot parameter are derived using the model. For R CMa, T2 was found to increase towards the near IR wavelengths, from the optical bands. This is interpreted as due to the presence of localized gas in the system. Also T2 derived from the Hα light curves is found to be higher than that derived from the neighbouring bands. This is explained as due to the difference in the photospheric absorption of Hα in the photospheres of the primary and the secondary. The moments of primary minima follow the periodic O-C curve observed for R CMa, giving more faith in the presence of a third body in the system, which was proposed before. But the nature of the third body, if present, is still uncovered.