Ruprecht 147 DANCe I. Members, empirical isochrone, luminosity and mass
  distributions
  Context. Ruprecht 147 is the oldest (2.5 Gyr) open cluster in the solar
vicinity (< 300 pc), making it an important target for stellar evolution
studies and exoplanet searches. Aims. Derive a census of members and the
luminosity, mass, and spatial distributions of the cluster. Methods. We use an
astro-photometric data set including all available information from the
literature together with our own observations. We process the data with an
updated version of an existent membership selection methodology. Results. We
identify 259 high-probability candidate members, including 58 previously
unreported. All these candidates cover the luminosity interval between G > 6
mag to i< 21 mag. The cluster luminosity and mass distributions are derived
with an unprecedented level of details allowing us to recognize, among other
features, the Wielen dip. The mass distribution in the low-mass regime drops
sharply at 0.4 $M_{\odot}$ even though our data are sensitive to stellar masses
down to 0.1 $M_{\odot}$, suggesting that most very-low-mass members left the
cluster as the result of its dynamical evolution. In addition, the cluster is
highly elongated (ellipticity $\sim$ 0.5) towards the galactic plane, and mass
segregated. Conclusions. Our combined Gaia+DANCe data set allows us to obtain
an extended list of cluster candidate members, and to derive luminosity, mass
and projected spatial distributions in the oldest open cluster of the solar
vicinity.
