Issue |
A&A
Volume 428, Number 3, December IV 2004
|
|
---|---|---|
Page(s) | 1027 - 1037 | |
Section | Astronomical instrumentation | |
DOI | https://doi.org/10.1051/0004-6361:20041536 | |
Published online | 07 December 2004 |
The Hamburg/ESO R-process Enhanced Star survey (HERES)*
I. Project description, and discovery of two stars with strong enhancements of neutron-capture elements
1
Hamburger Sternwarte, Universität Hamburg, Gojenbergsweg 112, 21029 Hamburg, Germany e-mail: nchristlieb@hs.uni-hamburg.de
2
Department of Astronomy and Space Physics, Uppsala University, Box 515, 75120 Uppsala, Sweden
3
Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824, USA
4
Research School of Astronomy & Astrophysics, Australian National University, Cotter Road, Weston, ACT 2611, Australia
5
Observatoire de Paris, GEPI and URA 8111 du CNRS, 92195 Meudon Cedex, France
6
Astronomical Observatory, NBIfAFG, Juliane Meries Vej 30, 2100 Copenhagen, Denmark
7
Nordic Optical Telescope Scientific Association, Apartado 474, 38 700 Santa Cruz de La Palma, Spain
8
Universitäts-Sternwarte München, Scheinerstrasse 1, 81679 München, Germany
9
Institute of Astronomy, Russian Academy of Sciences, Pyatnitskaya 48, 109017 Moscow, Russia
10
School of Physics and Astronomy, University of Minnesota, Minneapolis, MN 55455, USA
11
Departamento de Astronomia Instituto de Astronomia, Geofísica e Ciências Atmosféricas, Universidade de São Paulo, 05508-900 São Paulo SP, Brazil
12
Division of Geophysics and Planetary Sciences, California Institute of Technology, Pasadena, CA91125, USA
13
Institut für Kernchemie, Universität Mainz, 55128 Mainz, Germany
14
VISTARS HGF – Virtual Institute for Nuclear Structure and Nuclear Astrophysics, Mainz, Germany
15
Lund University Box 43, 22100 Lund, Sweden
16
Center for Space Astrophysics, Yonsei University, Seoul 120-749, Korea
17
Space Astrophysics Laboratory, California Institute of Technology, MC 405-47, Pasadena, CA 91125, USA
18
Department of Physics and Astronomy, Open University, Walton Hall, Milton Keynes, MK7 6AA, UK
Received:
25
June
2004
Accepted:
11
August
2004
We report on a dedicated effort to identify and study metal-poor stars
strongly enhanced in r-process elements ( dex; hereafter
r-II stars), the Hamburg/ESO R-process Enhanced Star survey
(HERES). Moderate-resolution (~2 Å) follow-up spectroscopy has been
obtained for metal-poor giant candidates selected from the Hamburg/ESO
objective-prism survey (HES) as well as the HK survey to identify sharp-lined
stars with
dex. For several hundred confirmed metal-poor
giants brighter than
mag (most of them from the HES),
“snapshot” spectra (
;
per pixel) are being
obtained with VLT/UVES, with the main aim of finding the
% r-II
stars expected to be among them. These are studied in detail by means of
higher resolution and higher
spectra. In this paper we describe
a pilot study based on a set of 35 stars, including 23 from the HK survey, eight
from the HES, and four comparison stars. We discovered two new r-II stars, CS 29497-004
(
) and CS 29491-069 (
). A first abundance analysis of CS 29497-004 yields that its abundances of Ba
to Dy are on average enhanced by 1.5 dex with respect to iron and the Sun
and match a scaled solar r-process pattern well, while Th is underabundant
relative to that pattern by 0.3 dex, which we attribute to radioactive
decay. That is, CS 29497-004 seems not to belong to the class of r-process enhanced
stars displaying an “actinide boost”, like CS 31082-001 (Hill et al. 2002),
or CS 30306-132 (Honda et al. 2004b). The abundance pattern agrees well with
predictions of the phenomenological model of Qian & Wasserburg.
Key words: surveys / stars: abundances / stars: population II / Galaxy: abundances / Galaxy: halo
© ESO, 2004
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