A kinematic view of NGC 1261: structural parameters, internal
  dispersion, absolute proper motion and Blue Straggler Stars
  We constructed a Hubble Space Telescope (HST) astro-photometric catalog of
the central region of the Galactic globular cluster NGC 1261. This catalog,
complemented with Gaia DR2 data sampling the external regions, has been used to
estimate the structural parameters of the system (i.e., core, half-mass, tidal
radii and concentration) from its resolved star density profile. We computed
high-precision proper motions thanks to multi-epoch HST data and derived the
cluster velocity dispersion profile in the plane of the sky for the innermost
region, finding that the system is isotropic. The combination with
line-of-sight information collected from spectroscopy in the external regions
provided us with the cluster velocity dispersion profile along the entire
radial extension. We also measured the absolute proper motion of NGC 1261 using
a few background galaxies as a reference. The radial distribution of the Blue
Straggler Star population shows that the cluster is in a low/intermediate phase
of dynamical evolution.
