First stars

XVI. HST/STIS abundances of heavy elements in the uranium-rich metal-poor star CS 31082-001^⋆,⋆⋆

¹ Universidade de São Paulo, IAG, Rua do Matão 1226, Cidade Universitária, 05508-900 São Paulo, Brazil
e-mail: cesar.mello@usp.br
² GEPI, Observatoire de Paris, CNRS, UMR 8111, 92195 Meudon Cedex, France
³ Zentrum für Astronomie der Universität Heidelberg, Landessternwarte, Königstuhl 12, 69117 Heidelberg, Germany
⁴ Laboratoire Lagrange, UMR 7293, Université de Nice Sophia-Antipolis, CNRS, Observatoire de la Côte d’Azur, 06300 Nice, France
⁵ National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, 181-8588 Tokyo, Japan
⁶ European Southern Observatory, Karl Schwarzschild Strasse 2, 85748 Garching bei München, Germany
⁷ LUPM, CNRS, UMR 5299, Université de Montpellier II, 34095 Montpellier Cedex 05, France
⁸ GEPI, Observatoire de Paris, CNRS, UMR 8111, 61 Av. de l’Observatoire, 75014 Paris, France
⁹ The Niels Bohr Institute, Juliane Maries Vej 30, 2100 Copenhagen, Denmark
¹⁰ Nordic Optical Telescope, Apartado 474, 38700 Santa Cruz de La Palma, Spain
¹¹ University of Texas at Austin, Department of Astronomy, Austin, TX 78712, USA
¹² National Optical Astronomy Observatory, Tucson, MI 85719, USA
¹³ Michigan State University, Department of Physics & Astronomy, and JINA, Joinst Institute for Nuclear Physics, East Lansing, MI 48824, USA
¹⁴ INAF – Osservatorio Astronomico di Trieste, via Tiepolo 11, 34143 Trieste, Italy

Received: 5 July 2012
Accepted: 8 November 2012

Abstract

Context. The origin and site(s) of the r-process nucleosynthesis is(are) still not known with certainty, but complete, detailed r-element abundances offer our best clues. The few extremely metal-poor (EMP) stars with large r-element excesses allow us to study the r-process signatures in great detail, with minimal interference from later stages of Galactic evolution. CS 31082-001 is an outstanding example of the information that can be gathered from these exceptional stars.

Aims. Here we aim to complement our previous abundance determinations for third-peak r-process elements with new and improved results for elements of the first and second r-process peaks from near-UV HST/STIS and optical UVES spectra. These results should provide new insight into the nucleosynthesis of the elements beyond iron.

Methods. The spectra were analyzed by a consistent approach based on an OSMARCS LTE model atmosphere and the Turbospectrum spectrum synthesis code to derive abundances of heavy elements in CS 31082-001, and using updated oscillator strengths from the recent literature. Synthetic spectra were computed for all lines of the elements of interest to check for proper line intensities and possible blends in these crowded spectra. Our new abundances were combined with the best previous results to provide reliable mean abundances for the first and second-peak r-process elements.

Results. We present new abundances for 23 neutron-capture elements, 6 of which – Ge, Mo, Lu, Ta, W, and Re – have not been reported before. This makes CS 31082-001 the most completely studied r-II star, with abundances for a total of 37 neutron-capture elements. We also present the first NLTE+3D abundance of lead in this star, further constraining the nature of the r-process.