Locations of X-ray sources in globular clusters

We have used the SAS 3 X-ray observatory to measure the positions of the X-ray sources in the globular clusters NGC 1851, 6441, 6624, 6712, and 7078. The derived positions have error circles with 90% confidence radii of 20'' or 30'' which, in each case, include the optical center of the cluster. The results of a statistical analysis demonstrate that the X-ray sources are more concentrated toward the cluster centers than the visible stars and are therefore more massive than those stars