The Gaia-ESO survey: Placing constraints on the origin of r-process elements

¹ INAF – Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy
e-mail: mathieu.van+der+swaelmen@inaf.it, laura.magrini@inaf.it
² Institute of Theoretical Physics and Astronomy, Vilnius University, Sauletekio av. 3, 10257 Vilnius, Lithuania
³ Dipartimento di Fisica, Sezione di Astronomia, Università di Trieste, Via G. B. Tiepolo 11, 34143 Trieste, Italy
⁴ INAF, Osservatorio Astronomico di Trieste, Via Tiepolo 11, 34143 Trieste, Italy
⁵ INFN, Sezione di Trieste, Via A. Valerio 2, 34127 Trieste, Italy
⁶ INAF – Osservatorio Astrofisico d’Abruzzo, via Maggini snc, 64100 Teramo, Italy
⁷ INFN – Sezione di Perugia, via A. Pascoli, 06123 Perugia, Italy
⁸ Goethe University Frankfurt, Max-von-Laue-Strasse 1, Frankfurt am Main 60438, Germany
⁹ Lund Observatory, Department of Astronomy and Theoretical Physics, Box 43 22100 Lund, Sweden
¹⁰ Max Planck Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany
¹¹ Niels Bohr International Academy, Niels Bohr Institute, University of Copenhagen Blegdamsvej 17, 2100 Copenhagen, Denmark
¹² INAF – Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, via Gobetti 93/3, 40129 Bologna, Italy
¹³ Departamento de Astrofísica, Centro de Astrobiología (CSIC-INTA), ESAC Campus, Camino Bajo del Castillo s/n, 28692 Villanueva de la Cañada, Madrid, Spain
¹⁴ Leibniz-Institut für Astrophysik Potsdam, An der Sternwarte 16, 14482 Potsdam, Germany
¹⁵ Department of Physics and Astronomy, Division of Astronomy and Space Physics, Angstrom laboratory, Uppsala University, Box 516 75120 Uppsala, Sweden
¹⁶ Instituto de Astrofísica de Canarias, 38205 La Laguna, Tenerife, Spain
¹⁷ Departamento de Astrofísica, Universidad de La Laguna, 38206 La Laguna, Tenerife, Spain
¹⁸ Nicolaus Copernicus Astronomical Center, Polish Academy of Sciences, ul. Bartycka 18, 00-716 Warsaw, Poland
¹⁹ INAF – Padova Observatory, Vicolo dell’Osservatorio 5, 35122 Padova, Italy

Received: 12 April 2022
Accepted: 7 July 2022

Abstract

Context. A renewed interest in the origin of r-process elements has been stimulated by the multi-messenger observation of the gravitational event GW170817, with the detection of both gravitational waves and electromagnetic waves corresponding to the merger of two neutron stars. Such a phenomenon has been proposed as one of the main sources of the r-process. However, the origin of the r-process elements at different metallicities is still under debate.

Aims. We aim at investigate the origin of the r-process elements in the Galactic thin-disc population.

Methods. From the sixth internal data release of the Gaia-ESO, we have collected a large sample of Milky Way (MW) thin- and thick-disc stars for which abundances of Eu, O, and Mg are available. The sample consists of members of 62 open clusters (OCs), located at a Galactocentric radius between ∼5 kpc and ∼20 kpc in the disc, in the metallicity range [ − 0.5, 0.4], and covering an age interval from 0.1 to 7 Gy, and about 1300 Milky Way disc field stars in the metallicity range [ − 1.5, 0.5]. We compare the observations with the results of a chemical evolution model, in which we varied the nucleosynthesis sources for the three elements considered.

Results. Our main result is that Eu in the thin disc is predominantly produced by sources with short lifetimes, such as magneto-rotationally driven SNe. There is no strong evidence for additional sources at delayed times.

Conclusions. Our findings do not imply that there cannot be a contribution from mergers of neutron stars in other environments, as in the halo or in dwarf spheroidal galaxies, but such a contribution is not needed to explain Eu abundances at thin-disc metallicities.