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Even-to-odd Barium Isotope Ratios in Thick Disk and Halo Stars as a Constraint to r- and s-process Nucleosynthesis

Published online by Cambridge University Press:  23 December 2005

Lyudmila I. Mashonkina  and
Gang Zhao
Lyudmila I. Mashonkina
Affiliation:
Institute of Astronomy, Russian Academy of Science, Pyatnitskaya 48, 119017 Moscow, Russia email: [email protected] National Astronomical Observatories Chinese Academy of Sciences, A20 Datun Road, Chaoyang District, Beijing 100012, China email: [email protected]
Gang Zhao
Affiliation:
National Astronomical Observatories Chinese Academy of Sciences, A20 Datun Road, Chaoyang District, Beijing 100012, China email: [email protected]
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Abstract

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We present the even-to-odd Ba isotope ratios in 16 thick disk and 3 halo stars as determined from hyperfine structure (HFS) seen in the Ba II resonance line λ 4554. We find in our stars a higher fraction of the odd Ba isotopes compared with the solar one 18% (Cameron 1982): 35% in the halo stars and between 25% and 53% in the thick disk stars. There is a hint of increasing this value with the Eu/Fe abundance ratio growth. Based on the r-process even-to-odd Ba isotope ratio 54 : 46 (Arlandini, Käppeler, Wisshak, et al. 1999) we deduce the ratio of the s/r-process contribution to barium in the thick disk stars as 30 : 70 (±24%).

Keywords

Nuclear reactionsnucleosynthesisabundancesstars: abundances
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 1 , Symposium S228: From Lithium to Uranium: Elemental Tracers of Early Cosmic Evolution , May 2005 , pp. 491 - 492
Copyright
© 2005 International Astronomical Union