Year: 1998
Type: article
Abstract: New, improved, barium abundances for 33 extremely metal-poor halo stars from the 1995 sample of McWilliam et al. have been computed. The mean [Ba/Eu] ratio for stars with [Fe/H] ≤ -2.4 is -0.69 ± 0.06 dex, consistent with pure r -process nucleosynthesis within the measurement uncertainties. Although the [Sr/Fe] and [Ba/Fe] abundance ratios span a range of 2.6 dex, the mean values are approximately constant with [Fe/H]. This is consistent with a model of chemical evolution in which the parent clouds were enriched by small numbers of supernova events. In this model, the decreasing heavy-element dispersion with increasing [Fe/H] is simply due to the averaging of element yields from many supernovae at higher [Fe/H]; however, it is necessary to increase the number of extremely metal-poor stars known in order to confirm this picture. In addition to the random Sr component from the r -process, the [Sr/Ba] ratios indicate that there is a second, also random, source of Sr from an as yet unidentified nucleosynthesis site.
Source: The Astronomical Journal
DOI: 10.1086/300289
Author: Andrew McWilliam
Institutions: Carnegie Institution for Science, Carnegie Observatories
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: bronze
OpenAlex ID: W2039278128