Ruprecht 147 DANCe

J Olivares,N Miret-Roig,A Berihuete,D Barrado,N Huélamo,Y Beletsky,M Tamura,S Serre,J.-C Cuillandre,L M Sarro,E Bertin,H Bouy,L Allen

doi:10.1051/0004-6361/201834924

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.

Highlights

Discovered by John Herschel in 1833 (Herschel 1833), Ruprecht 147, known as NGC 6774, is one of the oldest open clusters in the solar vicinity (2.5 Gyr at 300 pc, Curtis et al 2013)
The improved membership selection methodology introduced in the previous section provided us with a list of candidate members for each of our data sets
We analyse these candidate members, compare the empirical isochrones they produce with theoretical ones, and derive their luminosity, mass and spatial distributions

Summary

Introduction

Discovered by John Herschel in 1833 (Herschel 1833), Ruprecht 147, known as NGC 6774, is one of the oldest open clusters in the solar vicinity (2.5 Gyr at 300 pc, Curtis et al 2013). Its scientific potential is plainly revealed in the work of Curtis et al (2013). In their extensive astrometric, photometric and spectroscopic analysis of the cluster properties, these authors identified 108 candidate members, derived an improved distance modulus of m − M = 7.35 ± 0.1 mag, an extinction of AV = 0.25 ± 0.05 mag, a super-Solar metallicity of [M/H] = +0.07 ± 0.03 dex, and an age of t = 2.5 ± 0.25 Gyr

Objectives

Results

Conclusion