The Gaia-ESO Survey: Calibrating the lithium–age relation with open clusters and associations

II. Expanded cluster sample and final membership selection^★,★★

¹ Departamento de Física de la Tierra y Astrofísica and IPARCOS-UCM (Instituto de Física de Partículas y del Cosmos de la UCM), Facultad de Ciencias Físicas, Universidad Complutense de Madrid, 28040 Madrid, Spain
e-mail: mlgutierrez@ucm.es
² Centro de Astrobiología (CSIC/INTA), Instituto Nacional de Técnica Aeroespacial, Ctra de Torrejón a Ajalvir, km 4, 28850 Torrejón de Ardoz, Madrid, Spain
³ Instituto de Astrofísica de Canarias (IAC), 38205 La Laguna, Tenerife, Spain
⁴ Universidad de la Laguna, Dept. Astrofísica, 38206 La Laguna, Tenerife, Spain
⁵ Hamburger Sternwarte, Gojenbergsweg 112, 21029 Hamburg, Germany
⁶ INAF – Osservatorio Astrofisico di Catania, via S. Sofia 78, 95123 Catania, Italy
⁷ Università di Catania, Dipartimento di Fisica e Astronomia, Sezione Astrofisica, Via S. Sofia 78, 95123 Catania, Italy
⁸ Institut für Astronomie und Astrophysik, Eberhard Karls Universität, Sand 1, 72076 Tübingen, Germany
⁹ INAF – Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy
¹⁰ Nicolaus Copernicus Astronomical Center, Polish Academy of Sciences, ul. Bartycka 18, 00-716 Warsaw, Poland
¹¹ Observational Astrophysics, Division of Astronomy and Space Physics, Department of Physics and Astronomy, Uppsala University, Box 516, 751 20 Uppsala, Sweden
¹² Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK
¹³ Instituto de Astrofísica de Andalucía (CSIC), Glorieta de la Astronomía s/n, Granada 18008, Spain
¹⁴ Centro de Astrobiología, CSIC-INTA, Camino bajo del castillo s/n, 28692, Villanueva de la Canãda, Madrid, Spain
¹⁵ INAF – Osservatorio Astronomico di Palermo, Piazza del Parlamento, 1, 90134 Palermo, Italy
¹⁶ Lund Observatory, Division of Astrophysics, Department of Physics, Lund University, Box 43, 22100 Lund, Sweden
¹⁷ INAF – Rome Astronomical Observatory (OAR), Via di Frascati, 33, 00044 Monte Porzio Catone, Italy
¹⁸ INAF – Osservatorio Astronomico di Padova, Vicolo dell'Osservatorio 5, 35122 Padova, Italy
¹⁹ School of Physical and Chemical Sciences – Te Kura Matü, University of Canterbury, Private Bag 4800, Christchurch 8140, New Zealand
²⁰ 114, 10 College Walk, School of Physics and Astronomy, Monash University, Monash, VIC 3800, Australia
²¹ European Space Agency (ESA), European Space Research and Technology Centre (ESTEC), Keplerlaan 1, 2201 AZ Noordwijk, The Netherlands
²² GEPI, Observatoire de Paris, CNRS, Université Paris Diderot, 5 Place Jules Janssen, 92190 Meudon, France
²³ Dipartimento di Fisica e Astronomia, Università di Padova, Vicolo dell'Osservatorio 3, 35122 Padova, Italy

Received: 31 October 2023
Accepted: 27 January 2024

Abstract

Context. The Li abundance observed in pre-main sequence and main sequence late-type stars is strongly age-dependent, but also shows a complex pattern depending on several parameters, such as rotation, chromospheric activity, and metallicity. The best way to calibrate these effects, and with the aim of studying Li as an age indicator for FGK stars, is to calibrate coeval groups of stars, such as open clusters (OCs) and associations.

Aims. We present a considerable target sample of 42 OCs and associations – with an age range from 1 Myr to 5 Gyr – observed within the Gaia-ESO survey (GES), and using the latest data provided by GES iDR6 and the most recent release of Gaia that was then available, EDR3. As part of this study, we update and improve the membership analysis for all 20 OCs presented in our previous article.

Methods. We perform detailed membership analyses for all target clusters to identify likely candidates, using all available parameters provided by GES, complemented with detailed bibliographical searches, and based on numerous criteria: from radial velocity distributions, to the astrometry (proper motions and parallaxes) and photometry provided by Gaia, to gravity indicators (log g and the γ index), [Fe/H] metallicity, and Li content in diagrams of (Li equivalent widths) EW(Li) versus T_eff.

Results. We obtain updated lists of cluster members for the whole target sample, as well as a selection of Li-rich giant contaminants obtained as an additional result of the membership process. Each selection of cluster candidates was thoroughly contrasted with numerous existing membership studies using data from Gaia to ensure the most robust results.

Conclusions. These final cluster selections will be used in the third and last paper of this series, which reports the results of a comparative study characterising the observable Li dispersion in each cluster and analysing its dependence on several parameters, allowing us to calibrate a Li–age relation and obtain a series of empirical Li envelopes for key ages in our sample.