The Gaia-ESO Survey: Lithium measurements and new curves of growth^★,★★

¹ INAF – Osservatorio Astrofísico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy
e-mail: elena.franciosini@inaf.it
² Université Côte d’Azur, Observatoire de la Côte d’Azur, CNRS, Laboratoire Lagrange, Bd de l’Observatoire, CS 34229, 06304 Nice cedex 4, France
³ INAF – Osservatorio Astronomico di Roma, via Frascati 33, 00040 Monte Porzio Catone (RM), Italy
⁴ Lund Observatory, Department of Astronomy and Theoretical Physics, Box 43, SE-22100 Lund, Sweden
⁵ Max-Planck Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany
⁶ INAF – Osservatorio Astrofísico di Catania, via S. Sofia 78, 95123 Catania, Italy
⁷ Department of Astronomy, Stockholm University, AlbaNova University Center, SE-10691 Stockholm, Sweden
⁸ INAF – Osservatorio Astronomico di Palermo, Piazza del Parlamento 1, 90134 Palermo, Italy
⁹ Institute of Theoretical Physics and Astronomy, Vilnius University, Sauletekio av. 3, 10257 Vilnius, Lithuania
¹⁰ Dipartimento di Fisica e Astronomia, Sezione Astrofísica, Università di Catania, via S. Sofia 78, 95123 Catania, Italy
¹¹ Nicolaus Copernicus Astronomical Center, Polish Academy of Sciences, ul. Bartycka 18, 00-716 Warsaw, Poland
¹² Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, United Kingdom
¹³ Space Science Data Center - Agenzia Spaziale Italiana, via del Politecnico, s.n.c., 00133 Roma, Italy
¹⁴ Leibniz-Institut für Astrophysik Potsdam (AIP), An der Sternwarte 16, 14482 Potsdam
¹⁵ GEPI, Observatoire de Paris, Université PSL, CNRS, 5 Place Jules Janssen, 92195 Meudon, France
¹⁶ Astrophysics Group, Keele University, Keele, Staffordshire ST5 5BG, UK
¹⁷ European Space Agency (ESA), European Space Research and Technology Centre ESTEC), Keplerlaan 1, 2201 AZ Noordwijk, The Netherlands
¹⁸ Instituto de Astrofísica de Andalucía, CSIC, Glorieta de la Astronomía SNR, 18008 Granada, Spain
¹⁹ INAF – Osservatorio di Astrofísica e Scienza dello Spazio, via P. Gobetti 93/3, 40129 Bologna, Italy
²⁰ GEPI, Observatoire de Paris, PSL Research University, CNRS, 61 avenue de l’Observatoire, 75014 Paris, France
²¹ UPJV, Université de Picardie Jules Verne, 33 rue St Leu, 80080 Amiens, France
²² Observational Astrophysics, Division of Astronomy and Space Physics, Department of Physics and Astronomy, Uppsala University, Box 516, SE-75120 Uppsala, Sweden
²³ Institut d’Astronomie et d’Astrophysique, Université libre de Bruxelles, CP 226, Boulevard du Triomphe, 1050 Bruxelles, Belgium
²⁴ European Southern Observatory, Karl-Schwarzschild-Strasse 2, 85748 Garching bei München, Germany
²⁵ Niels Bohr International Academy, Niels Bohr Institute, University of Copenhagen, Blegdamsvej 17, 2100 Copenhagen Ø, Denmark
²⁶ Dipartimento di Fisica e Astronomia, Università di Padova, Vicolo dell’Osservatorio 2, 35122 Padova, Italy
²⁷ Núcleo de Astronomía, Facultad de Ingeniería y Ciencias, Universidad Diego Portales, Av. Ejército 441, Santiago, Chile
²⁸ European Organisation for Astronomical Research in the Southern Hemisphere, Alonso de Córdova 3107, Vitacura, Casilla 19001, Santiago 19, Chile
²⁹ Departamento de Ciencias Fisicas, Universidad Andres Bello, Fernandez Concha 700, Las Condes, Santiago, Chile
³⁰ INAF – Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio 5, 35122 Padova, Italy

Received: 31 August 2022
Accepted: 4 October 2022

Abstract

Context. The Gaia-ESO Survey (GES) is a large public spectroscopic survey that was carried out using the multi-object FLAMES spectrograph at the Very Large Telescope. The survey provides accurate radial velocities, stellar parameters, and elemental abundances for ~115 000 stars in all Milky Way components.

Aims. In this paper, we describe the method adopted in the final data release to derive lithium equivalent widths (EWs) and abundances.

Methods. Lithium EWs were measured using two different approaches for FGK and M-type stars, to account for the intrinsic differences in the spectra. For FGK stars, we fitted the lithium line using Gaussian components, while direct integration over a predefined interval was adopted for M-type stars. Care was taken to ensure continuity between the two regimes. Abundances were derived using a new set of homogeneous curves of growth that were derived specifically for GES, and which were measured on a synthetic spectral grid consistently with the way the EWs were measured. The derived abundances were validated by comparison with those measured by other analysis groups using different methods.

Results. Lithium EWs were measured for ~40 000 stars, and abundances could be derived for ~38 000 of them. The vast majority of the measures (80%) have been obtained for stars in open cluster fields. The remaining objects are stars in globular clusters, or field stars in the Milky Way disc, bulge, and halo.

Conclusions. The GES dataset of homogeneous lithium abundances described here will be valuable for our understanding of several processes, from stellar evolution and internal mixing in stars at different evolutionary stages to Galactic evolution.