Photometric observations of two very long period eclipsing binaries: AZ Cas and EE Cep

This paper reports new photometric observations of minima of two very long-period eclipsing systems: AZ Cas (P=3402) and EE Cep (P=2050). In order to match the observed depth of the primary minimum of AZ Cas we had to introduce a third light component. For EE Cep, the shape of the eclipse can be explained by a model that includes a dark precessing disk in the system. 1. The 1994 and 2003 eclipses of AZ Cas AZ Cas consists of an M0I supergiant and B0V hot component (Cowley, Hutchings, & Popper 1977). Its orbital period is 9.3 years and the light curve shows flat-bottomed minima of about 100 days duration. Cowley et al. (1977 and references therein) summarized the photometric data taken since AZ Cas was discovered by Ashbrook (1959) until the primary minimum which occurred in mid 70s. No significant light variations in UBVRI outside the eclipse have been found (Nha 1994; Lee & Gim 1994). The spectroscopic orbital parameters for the cool component revealed a very eccentric orbit (e= 0.55) and the mass function f(m) = 2.2 M (Cowley et al. 1977). Assuming this mass function and the mass of 14M for the hot component (a B0 Main Sequence star) the estimated mass ratio is q= 1.5 (MM0/MB0). The primary minimum in 1994 was observed at two observatories: Mt. Suhora observatory using the 60 cm Cassegrain telescope and a two-channel