Ruprecht 147 DANCe I. Members, empirical isochrone, luminosity, and mass distributions

Olivares, J., Bouy, H., Sarro, L. M., Miret Roig, N., Berihuete, A., Bertín, E., Barrado, D., Huelamo, N., Tamura, M., Allen, L., Beletsky, Y., Serre, S., Cuillandre, J. C. 2019. Ruprecht 147 DANCe I. Members, empirical isochrone, luminosity, and mass distributions. Astronomy and Astrophysics 625 DOI: 10.1051/0004-6361/201834924

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. We aim to derive a census of members and the luminosity, mass, and spatial distributions of the cluster.

Methods. We used an astro-photometric data set including all available information from the literature together with our own observations. We processed 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 greater than or similar to 6 mag and i less than or similar to 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-circle dot even though our data are sensitive to stellar masses down to 0.1 M-circle dot, 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 similar to 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.

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