IS THE CHANGING ORBITAL PERIOD OF EXO-0748-676 EVIDENCE FOR A TRIPLE SYSTEM

We present eclipse timing measurements of the low-mass X-ray binary EX O 0748-676 made with ASCA. These measurements, when combined with prev ious results, are consistent with the hypothesis that eclipse times ar e modulated by a third body. The parameters of the orbit of the postul ated third body are now apparently well constrained and will allow fur ther observations to effectively test the hypothesis that EXO 0748-676 is a triple system. The derived orbital parameters are such that, unl ess the inclination angle is very low, a third body in the system must have a mass less than the lower limit for a main-sequence star.