CaltechAUTHORS
Published December 4, 2004 | Version Published + Submitted
Journal Article Open

The Hamburg/ESO R-process Enhanced Star survey (HERES). I. Project description, and discovery of two stars with strong enhancements of neutron-capture elements

Creators

  • 1. ROR icon Universität Hamburg
  • 2. ROR icon Uppsala University
  • 3. ROR icon Michigan State University
  • 4. ROR icon Australian National University
  • 5. ROR icon Paris Observatory
  • 6. ROR icon Nordic Optical Telescope Scientific Association
  • 7. ROR icon Ludwig-Maximilians-Universität München
  • 8. ROR icon Institute of Astronomy
  • 9. ROR icon University of Minnesota
  • 10. ROR icon Universidade de São Paulo
  • 11. ROR icon California Institute of Technology
  • 12. ROR icon Johannes Gutenberg University of Mainz
  • 13. ROR icon Lund University
  • 14. ROR icon Yonsei University
  • 15. ROR icon The Open University

Abstract

We report on a dedicated effort to identify and study metal-poor stars strongly enhanced in r-process elements ([r/Fe]>1 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 ([Fe/H]<-2.5 dex. For several hundred confirmed metal-poor giants brighter than B ~ 16.5 mag (most of them from the HES), "snapshot" spectra (R ~ 20,000; S/N ~ 30 per pixel) are being obtained with VLT/UVES, with the main aim of finding the 2-3% r-II stars expected to be among them. These are studied in detail by means of higher resolution and higher S/N 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 ([Eu/Fe] = 1.64 ± 0.22) and CS 29491-069 ([Eu/Fe] = 1.08 ± 0.23). 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.

Additional Information

© 2004 ESO. Article published by EDP Sciences. Received 25 June 2004. Accepted 11 August 2004. Based in large part on observations collected at the European Southern Observatory, Paranal, Chile (proposal number 68.B-0320). We are grateful to the ESO staff at Paranal and Garching for obtaining the VLT/UVES observations and reducing the data, respectively. Computations of tailored MARCS models by M. Mizuno-Wiedner, B. Edvardsson and B. Gustafsson are acknowledged. We are grateful to K. Eriksson and B. Edvardsson for technical help with the abundance analysis programs, and B. Gustafsson for many valuable comments. J. Cohen kindly derived an effective temperature for CS 29497−004 from broad-band photometry for us. We are indebted to A. Frebel for careful proofreading of an earlier version of the manuscript. N.C. acknowledges financial support through a Henri Chretien International Research Grant administered by the American Astronomical Society, from Deutsche Forschungsgemeinschaft under grants Re 353/44-1 and CH 214/3-1, and a Marie Curie Fellowship of the European Community program Improving Human Research Potential and the Socio-Economic Knowledge under contract number HPMF-CT-2002-01437. T.C.B. acknowledges partial funding for this work from grants AST 00-98508 and AST 00-98549 awarded by the US National Science Foundation and from award PHY 02-16783, Physics Frontiers Center/Joint Institute for Nuclear Astrophysics (JINA). P.B. acknowledges the support of the Swedish Research Council. A.J.K. acknowledges support from the Studienstiftung des deutschen Volkes and the Akademie Leopoldina under grant BMBF-LPD 9901/8-87. S.R. thanks the Brazilian Institutions FAPESP and CNPq for partial financial support. The work by G.J.W. was supported by DOE DE-FG03-88ER 13851, Caltech Division Contribution No. 9011(1116).

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Additional details

Identifiers

Eprint ID
43092
Resolver ID
CaltechAUTHORS:20131219-102017506

Related works

Describes
http://arxiv.org/abs/astro-ph/0408389 (URL)

Funding

American Astronomical Society
Deutsche Forschungsgemeinschaft (DFG)
Re 353/44-1
Deutsche Forschungsgemeinschaft (DFG)
CH 214/3-1
European Community Marie Curie Fellowship
HPMF-CT-2002-01437
NSF
AST 00-98508
NSF
AST 00-98549
NSF
PHY 02-16783
Swedish Research Council
Studienstiftung des deutschen Volkes and the Akademie Leopoldina
BMBF-LPD 9901/8-87
FAPESP (Brazil)
CNPq (Brazil)
Department of Energy (DOE)
DE-FG03-88ER 13851

Dates

Created
2013-12-19
Created from EPrint's datestamp field
Updated
2021-11-10
Created from EPrint's last_modified field

Caltech Custom Metadata

Other Numbering System Name
Lunatic Asylum Lab
Other Numbering System Identifier
1116