  We study analytically a gravitational lens due to a deformed star, which is
modeled by using a monopole and a quadrupole moment. Positions of the images
are discussed for a source on the principal axis. We present explicit
expressions for the lens equation for this gravitational lens as a single real
tenth-order algebraic equation. Furthermore, we compute an expression for the
caustics as a discriminant for the polynomial. Another simple parametric
representation of the caustics is also presented in a more tractable form. A
simple expression for the critical curves is obtained to clarify a topological
feature of the critical curves; the curves are simply connected if and only if
the distortion is sufficiently large.
