A GRAVITATIONAL LENS MODEL FOR B-1422+231

We investigate simple gravitational lens models for the recently disco vered quadruple QSO B 1422+23 1. The image configuration in this multi ple QSO system indicates that the gravitational deflector has a consid erable ellipticity; we therefore explore lensing models based on ellip tical mass distributions. Employing a simple fitting procedure, we sho w that (1) our models cannot satisfactorily account for the details of the image configuration, in particular, the flux ratios are difficult to reproduce; (2) Our best model is a combination of an elliptical de flector and externally applied shear; the direction of the shear is in accordance with the position of two galaxies detected near the QSO im ages, and may well be produced by them. If this interpretation is corr ect, our best model is in fact quite similar to the model of Hogg & Bl andford, except that we account for the ellipticity of the main deflec tor, which reduces the mass of the nearby galaxies to produce the nece ssary shear. The fact that the models do not improve if the position o f the lens center is allowed to vary from its observed position is a s trong argument in favour of it being indeed the main lensing galaxy.