Fokker-Planck models of NGC 6397 -- B. The globular cluster

Abstract

This is the second of two papers presenting a detailed examination of Fokker-Planck models for the globular cluster NGC 6397 and is concerned with extracting information on the cluster from the models. The models give a current cluster mass of $6.6\pm 0.5\times 10^4 \Msolar$ of which about 2500 \Msolar\ is in neutron stars. This mass gives a $V$-band mass-to-light ratio of 1.2 in solar units. The models and data provide weaker estimates of the structural parameters, but suggest that the core radius is less than 0.3 pc (11\arcsec) and the tidal radius is $17\pm 4$ pc. In turn, by assuming a flat rotation curve for the galaxy, the mass and tidal radius suggest that the latter was set at a distance of 2.5 kpc from the galactic center.