Light Synthesis modeling of close binary stars.

Recent years have seen substantial progress in understanding residual departures of observed light curves, for close binary stars without degenerate components, from the canonical Roche model. Examples of observed departures include the O'Connell effect and "anomalies" in W Ursae Majoris systems. A test on W Ursae Majoris data, with 89 spots, produces light curves and color curves that give an appreciably poorer representation of the observations than the hot secondary model. Sparse observational data at 330, 250, and 220 nm from the Astronomical Netherlands Satellite have historically been interpreted to provide support for the starspot model. However, simulation of the individual light curves demonstrates inability of either the hot secondary or starspot model to represent those data. The light curve amplitudes require enhanced surface brightness near the neck region, which will be eclipsed at both minima. Thus, the problem of the W-type light curves of W Ursae Majoris remains incompletely resolved.