DETECTION OF AN ULTRAVIOLET AND VISIBLE COUNTERPART OF THE NGC-6624 X-RAY BURSTER

We have detected, in images taken with the HST FOC, the UV and optical counterpart of the X-ray source 4U 1820-30 in the globular cluster NG C 6624. Astrometric measurements place this object 2 sigma from the X- ray position of 4U 1820-30. The source dominates a far-UV FOC image an d has the same flux at 1400 angstrom as was seen through the large IUE aperture by Rich et al. (1993). It has a B magnitude of 18.7 but is n ot detected in V. It is 0.66'' from the center of NGC 6624, a fact tha t may change the interpretation of the P of the 11 minute binary orbit . The flux drops between 1400 and 4300 angstrom at a rate that is near ly as steep as that of a Rayleigh-Jeans curve. The flux is far too lar ge to come from the neutron star directly but could accord with radiat ion from a heated accretion disk and/or the heated side of the compani on star.