THE ECLIPSING BINARY AI PHOENICIS - NEW RESULTS BASED ON AN IMPROVED LIGHT-CURVE ANALYSIS PROGRAM

The 24.6 day eclipsing binary AI Phe contains two sharp-lined stars of comparable luminosity which undergo total eclipse, and yet are well s eparated. Radial velocity, photometric, and ultraviolet observations o f this star have been remodeled using our improved version of the Wils on-Devinney code on the University of Calgary's Cyber 205 and Myrias S PS-2 computers. This version now has a new atmospheres option which ma kes use of Kurucz' model atmospheres to approximate the surface fluxes of the two stars. With the option, light curve fitting is now demonst rably improved for optical wavelengths. Rough empirical corrections re sult in still further improvement, with smaller discrepancies in U and u than are found using either the blackbody approximation or the prev iously used (Carbon-Gingerich) atmospheres option. For a specified tem perature, wavelength, and log g, interpolation is performed within a t able of values representing the ratio of blackbody to stellar atmosphe re flux. The model atmosphere option simulates fluxes in Stromgren uvb y or Johnson UBV bandpasses, as well as in other band-passes with widt hs DELTA-log-lambda = 0.1 in the range 0.316 to 3.550-mu-m, and DELTA- log-lambda = 0.05 in the UV (at 10 specified wavelengths from 0.100 to 0.282-mu-m). The limb darkening of the hotter component in the far UV as it undergoes total eclipse is also investigated and compared with Kurucz models.