A GENERALIZED-MODEL FOR GRAVITATIONAL MICROLENSING OF STARS - ANALYSIS OF THE OGLE DATA

The effect of the annual parallactic displacement of a star with finit e angular size and a given linear limb-darkening law on the star's mic rolensing light curve is examined. For some combinations of parameters , the parallactic displacement can give rise to asymmetry in the lensi ng curve and affect the identification of microlensing events. A proce dure for the selection of a generalized, nonlinear model for this phen omenon with separate determination of the photometric and geometric pa rameters of the problem is proposed. This procedure makes it possible to derive from an observed lensing curve estimates of the angular diam eter of the star, the parameters of the relative motion of the lens an d star, and the difference in the annual parallaxes of the lens and th e star in units of the Einstein cone radius. Knowledge of any one of t hese parameters, in turn, enables determination of the angular radius of the Einstein cone of the gravitational lens. The question of estima ting the confidence limits for the model parameters is discussed. Anal ysis of the microlensing curve for the bulge star OGLE-5 shows that th e model can fit the experimental data if the gravitational lens candid ate is a K5 dwarf.