The Chemical Composition and Age of the Metal-Poor Halo Star BD +17^\circ 3248

We have combined new high-resolution spectra obtained with the Hubble Space Telescope (HST) and ground-based facilities to make a comprehensive new abundance analysis of the metal-poor, halo star BD +17^\circ 3248. We have detected the third r-process peak elements osmium, platinum, and (for the fir...

Full description

Saved in:
Bibliographic Details
Published in:arXiv.org 2002-02
Main Authors: Cowan, John J, Sneden, Christopher, Burles, Scott, Ivans, Inese I, Beers, Timothy C, Truran, James W, Lawler, James E, Primas, Francesca, Fuller, George M, Pfeiffer, Bernd, Kratz, Karl-Ludwig
Format: Article
Language:English
Subjects:
Abundance
Chemical composition
Gold
Hubble Space Telescope
Metallicity
Nuclear capture
Organic chemistry
Osmium
Platinum
Radioisotopes
Silver
Solar system
Space telescopes
Stars
Stellar age
Thorium
Uranium
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:We have combined new high-resolution spectra obtained with the Hubble Space Telescope (HST) and ground-based facilities to make a comprehensive new abundance analysis of the metal-poor, halo star BD +17^\circ 3248. We have detected the third r-process peak elements osmium, platinum, and (for the first time in a metal-poor star) gold, elements whose abundances can only be reliably determined using HST. Our observations illustrate a pattern seen in other similar halo stars with the abundances of the heavier neutron-capture elements, including the third r-process peak elements, consistent with a scaled solar system r-process distribution. The abundances of the lighter neutron-capture elements, including germanium and silver, fall below that same scaled solar r-process curve, a result similar to that seen in the ultra-metal-poor star CS 22892--052. A single site with two regimes or sets of conditions, or perhaps two different sites for the lighter and heavier neutron-capture elements, might explain the abundance pattern seen in this star. In addition we have derived a reliable abundance for the radioactive element thorium. We tentatively identify U II at 3859 A in the spectrum of BD +17^\circ 3248, which makes this the second detection of uranium in a very metal-poor halo star. Our combined observations cover the widest range in proton number (from germanium to uranium) thus far of neutron-capture elements in metal-poor Galactic halo stars. Employing the thorium and uranium abundances in comparison with each other and with several stable elements, we determine an average cosmochronological age for BD +17^\circ 3248 of 13.8 +/- 4 Gyr, consistent with that found for other similar metal-poor halo stars.
ISSN:2331-8422
DOI:10.48550/arxiv.0202429