SS Lac in Open Cluster NGC 7209

Abstract

We present IUE observations in far ultraviolet region for SS Lac in open cluster NGC 7209. The IUE short wavelength spectrum and long wavelength spectrum were merged to produce an energy distribution curve between 1200A and 3200A. The curve has been unreddened to take out reddening effect. Then the surface temperature, gravity and abundance of SS Lac were determined based on the Kurucz model atmosphere. The photographic light curve produced before cessation of eclipse were analyzed for photometric solutions. We confirmed SS Lac is a member of open cluster NGC 7209 based on its possible distance. The main reason for the cessation of eclipse is the change of the system's orbital inclination rather than collisional merger of two stars.