Analyses of the currently noneclipsing binary SS Lacertae or SS Lacertae'seclipses

Confirmatory evidence for changing light-curve amplitude of the former ecli psing and current SB2 system SS Lac in the Open Cluster NGC 7209 has been u ncovered. Remeasured Harvard plate data and published and compiled data set s reveal that the depth of the primary minimum increased between the 1890s and 1902 and decreased in the 1920s and 1930s. A parabolic fitting of the a mplitude with phase predicts a maximum at 1911.5, with an eclipse onset at 1885.3 and eclipse cessation at 1937.8. We confirm the finding of Lehmann, that the system's inclination varies with time and that a central eclipse o ccurred similar to 1912, and we concur with Mossakovskaya that eclipses eff ectively ceased similar to 1940. Estimates of SS Lac on plates taken at Tas hkent between 1937 and 1940 further serve to confirm the result. Thus, SS L ac belongs to a small but elite class of triple systems in which changes du e to dynamical effects can be seen over a single human lifetime. In order t o explore the properties of the SS Lac system, recent radial velocity curve s and archival photographic and visual light curves have been analyzed with versions of the Wilson-Devinney code, augmented with a simplex routine to test solution uniqueness. The modeling solutions for the Dugan-Wright light curves ostensibly indicate that the former eclipsing system is composed of two early A stars of only slightly differing masses (2.57 +/- 0.16 and 2.5 9 +/- 0.19 M.) and effective surface temperatures (8750 +/- 300 [assumed fo r component 1] and 8542 +/- 309 K), but significantly different radii (2.38 +/- 0.02 and 3.63 +/- 0.07 R.) and luminosities (30 +/- 4 and 63 +/- 9 L.) for the hotter and cooler components, respectively. The light-curve soluti ons are compromised somewhat by variable eclipse depths over the ranges of dates of the data sets. This is especially true of the most complete light curve, that of Dugan & Wright; the others also suffer from incompleteness ( that of Wachmann) and high scatter (that of Kordylewski, Pagaczewski, & Sza franiec). As a consequence, small, temporal variations in such system prope rties as the eccentricity, argument of periastron, modified Roche potential s, luminosities, and third light level, cannot be ruled out from currently available data. However, solutions with WD95, a self-iterating, damped-leas t squares version of the Wilson-Devinney program, reveal optimized inclinat ions for the data sets that project an inclination variation of 0 degrees.1 6 yr(-1), but no evidence of apsidal motion. We find a distance for the sys tem of 898 +/- 95 pc, consistent with the value of Vansevicius et al. of 10 40 +/- 10 pc, and finally, on the bases of location on the sky, proper moti on, radial velocity, photometry, and properties deduced in the present stud y, we confirm its membership in the cluster NGC 7209.