abstract

[John Cowan <cowan@nhn.ou.edu>]

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\title{Nucleosynthesis}

\author{John J. Cowan}

\date{15 February 2006}

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\begin{abstract}
Abundance observations  indicate the presence of
neutron capture ({\it i.e.}, $s$- and $r$-process) elements in old Galactic halo
and globular cluster stars.
These observations provide insight into the nature of
the earliest generations of stars in the Galaxy -- the progenitors of the
halo stars --
responsible
for neutron-capture synthesis. Comparisons of abundance trends can be
used to understand the chemical evolution of the Galaxy and the nature
of heavy element nucleosynthesis. In addition age determinations, based upon
long-lived radioactive nuclei abundances, can now be obtained. 
These stellar abundance determinations  depend critically upon atomic 
data. Improved laboratory transition probabilities have 
been recently obtained for a number of elements. 
These new gf values have been used to greatly refine 
the solar photospheric abundances of, especially, rare-earth elements,
and has allowed for 
more reliable determinations of the abundances in metal-poor Galactic
halo stars. 
These newly determined stellar abundances
are consistent with a (relative)  Solar System 
$r$-process pattern,  
and are also consistent with abundance predictions
expected from such neutron-capture nucleosynthesis. 

This work has been supported in part by NSF 
and by STScI.
 
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