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We present a new identity card for the cluster NGC 6440 in the GalacticBulge. We have used a combination of high-resolution Hubble Space Telescopeimages, wide-field ground-based observations performed with the ESO-FORS2, andthe public survey catalog Pan-STARRS, to determine the gravitational center,projected density profile and structural parameters of this globular fromresolved star counts. The new determination of the cluster center differs by ~2" (corresponding to 0.08 pc) from the previous estimate, which was based onthe surface brightness peak. The star density profile, extending out to 700"from the center and suitably decontaminated from the Galactic fieldcontribution, is best-fitted by a King model with significantly largerconcentration ($c=1.86\pm0.06$) and smaller core radius ($r_c=6.4"\pm0.3"$)with respect to the literature values. By taking advantage of high-qualityoptical and near-infrared color-magnitude diagrams, we also estimated thecluster age, distance and reddening. The luminosity of the RGB-bump was alsodetermined. This study indicates that the extinction coefficient in the bulge,in the direction of the cluster has a value ($R_V=2.7$) that is significantlysmaller than that traditionally used for the Galaxy ($R_V=3.1$). Thecorresponding best-fit values of the age, distance and color excess of NGC 6440are 13 Gyr, 8.3 kpc and $E(B-V)\sim 1.27$, respectively. These newdeterminations also allowed us to update the values of the central($t_{rc}=2.5\ 10^7$ yr) and half-mass ($t_{rh}=10^9$ yr) relaxation times,suggesting that NGC 6440 is in a dynamically evolved stage.

A new identity card for the bulge globular cluster NGC 6440 from resolved star counts