The solar photospheric abundance of europium

Results from CO5BOLD  3D hydrodynamical model atmospheres

¹ Dipartimento di Astronomia, Università degli Studi di Bologna, Via Ranzani 1, 40127 Bologna, Italy e-mail: alessio.mucciarelli@studio.unibo.it
² GEPI, Observatoire de Paris, CNRS UMR 8111, Université Paris Diderot, Place Jules Janssen, 92190 Meudon, France e-mail: [elisabetta.caffau;hans.ludwig;piercarlo.bonifacio]@obspm.fr
³ Centre de Recherche Astrophysique de Lyon, UMR 5574 CNRS, Université de Lyon, École Normale Supérieure de Lyon, 46 allée d'Italie, 69364 Lyon Cedex 07, France e-mail: Bernd.Freytag@ens-lyon.fr
⁴ Istituto Nazionale di Astrofisica, Osservatorio Astronomico di Trieste, Via Tiepolo 11, 34143 Trieste, Italy

Received: 25 December 2007
Accepted: 6 March 2008

Abstract

Context. Europium is an almost pure r-process element, which may be useful as a reference in nucleocosmochronology.

Aims. Determine the photospheric solar abundance using CO5BOLD  3D hydrodynamical model atmospheres.

Methods. Disc-centre and integrated-flux observed solar spectra are used. The europium abundance is derived using equivalent-width measurements. As a reference, one-dimensional model atmospheres are in addition used.

Results. The europium photospheric solar abundance (0.52 ± 0.02) agrees with previous determinations. We determine the photospheric isotopic fraction of ¹⁵¹Eu to be 49% ± 2.3% using the intensity spectra, and 50% ± 2.3% using the flux spectra. This compares well to the meteoritic isotopic fraction 47.8%. We explore 3D corrections for dwarfs and sub-giants in the temperature range ~5000 K to ~6500 K and solar and 1/10-solar metallicities and find them to be negligible for all models investigated.

Conclusions. Our photospheric Eu abundance agrees well with previous determinations based on 1D models. This is in line with our conclusion that 3D effects for this element are negligible in the case of the Sun.