We present a new identity card for the cluster NGC 6440 in the Galactic Bulge. We have used a combination of high-resolution Hubble Space Telescope images, wide-field ground-based observations performed with the ESO-FORS2, and the public survey catalog Pan-STARRS to determine the gravitational center, projected density profile, and structural parameters of this globular from resolved star counts. The new determination of the cluster center differs by ∼2″ (corresponding to 0.08 pc) from the previous estimate, which was based on the surface brightness peak. The star density profile, extending out to 700″ from the center and suitably decontaminated from the Galactic field contribution, is best fit by a King model with a significantly higher concentration (c = 1.86 0.06) and smaller core radius (r _c = 6.″4 0.″3) with respect to the literature values. By taking advantage of high-quality optical and near-IR color–magnitude diagrams, we also estimated the cluster age, distance, and reddening. The luminosity of the red giant branch bump was also determined. 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 significantly lower than that traditionally used for the Galaxy (R _V = 3.1). The corresponding best-fit values of the age, distance, and color excess of NGC 6440 are 13 Gyr, 8.3 kpc, and E(B − V) ∼ 1.27. These new determinations also allowed us to update the values of the central (t _rc = 2.5 10⁷ yr) and half-mass (t _rh = 10⁹ yr) relaxation times, suggesting that NGC 6440 is in a dynamically evolved stage.

我们为银河凸起中的 NGC 6440 星团提供了一张新的身份证。我们结合使用高分辨率哈勃太空望远镜图像、使用 ESO-FORS2 进行的宽视场地面观测以及公共调查目录 Pan-STARRS 来确定重心、投影密度剖面和结构参数这个球状来自已解析的恒星计数。聚类中心的新确定与之前基于表面亮度峰值的估计相差 ∼2"（对应于 0.08 pc）。恒星密度分布从中心延伸到 700 英寸，并从银河场贡献中适当净化，最适合具有显着更高浓度 ( c = 1.86 0.06) 和更小的核心半径 ( r _c = 6.″4 0.″3) 相对于文献值。通过利用高质量的光学和近红外色阶图，我们还估计了星团年龄、距离和变红。还确定了红巨星分支凸起的光度。这项研究表明，星系团方向凸起的消光系数的值（ R _V = 2.7）明显低于传统上用于星系的消光系数（ R _V = 3.1）。NGC 6440 的年龄、距离和颜色过量的相应最佳拟合值为 13 Gyr、8.3 kpc 和E ( B - V ) ∼ 1.27。这些新的决定还使我们能够更新中央（ t _rc = 2.5 10 ⁷ yr) 和半质量 ( t _rh = 10 ⁹ yr) 弛豫时间，表明 NGC 6440 处于动态演化阶段。