Ruprecht 147 DANCe

I. Members, empirical isochrone, luminosity, and mass distributions^⋆

¹ Laboratoire d’astrophysique de Bordeaux, Univ. Bordeaux, CNRS, B18N, allée Geoffroy Saint-Hilaire, 33615 Pessac, France
e-mail: javier.olivares-romero@u-bordeaux.fr
² Department of Astronomy, The University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
³ National Astronomical Observatory of Japan, 2-21-1, Osawa, Mitaka, Tokyo 181-8588, Japan
⁴ Astrobiology Center, 2-21-1, Osawa, Mitaka, Tokyo 181-8588, Japan
⁵ National Optical Astronomy Observatory, 950 North Cherry Avenue, Tucson, AZ 85719, USA
⁶ Depto. de Inteligencia Artificial, UNED, Juan del Rosal, 16, 28040 Madrid, Spain
⁷ Institut d’Astrophysique de Paris, CNRS UMR 7095 and UPMC, 98bis bd Arago, 75014 Paris, France
⁸ Centro de Astrobiología, Dpto de Astrofísica, INTA-CSIC, ESAC Campus, Camino Bajo del Castillo s/n, 28692 Villanueva de la Cañada, Madrid, Spain
⁹ Dept. Statistics and Operations Research, University of Cádiz, Campus Universitario Río San Pedro s/n, 11510 Puerto Real, Cádiz, Spain
¹⁰ Las Campanas Observatory, Carnegie Institution of Washington, Colina el Pino, 601 Casilla, La Serena, Chile
¹¹ AIM Paris Saclay, CNRS/INSU, CEA/Irfu, Université Paris Diderot, Orme des Merisiers, France

Received: 19 December 2018
Accepted: 14 February 2019

Abstract

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. 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 ≳ 6 mag and 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_⊙ even though our data are sensitive to stellar masses down to 0.1 M_⊙, 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 ∼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.