As part of our campaign to determine the nature of the various source populations of the low-luminosity globular cluster X-ray sources , we have obtained a Chandra X-ray Observatory ACIS-S3 image of the globular cluster NGC 6440 .
We detect 24 sources to a limiting luminosity of \sim 2 \times 10 ^ { 31 } erg s ^ { -1 } ( 0.5–2.5 keV ) inside the cluster ’ s half-mass radius , all of which lie within \sim 2 core radii of the cluster center .
We also find excess emission in and around the core which could be due to unresolved point sources .
Based upon X-ray luminosities and colors , we conclude that there are 4–5 likely quiescent low-mass X-ray binaries and that most of the other sources are cataclysmic variables .
We compare these results to Chandra results from other globular clusters and find the X-ray luminosity functions differ among the clusters .