Surface photometry of the cores of globular clusters. I. NGC 6440

Results of picture processing of the globular cluster NGC 6440 are presented and discussed relative to the cluster's significance as a possible transient x-ray source. Processed images are presented illustrating the unusual central luminosity distribution, and a high-resolution color map of the center is given to demonstrate the behavior of B-V across the core. The central surface brightness and core radius are determined and the tidal radius is estimated from a mean luminosity profile in the B band. A color profile (B-V) indicates a possible slight trend toward bluer colors with increasing radius. An initial color-magnitude diagram is derived down to Vapprox. =19.0, apparently reaching just to the red horizontal branch. In addition to the cluster center, blue stars in the field are identified for further study as x-ray source candidates