Elements are produced in stars through a variety of processes; some are well known, others are still the object of active research. The elements Zirconium (Zr) and Yttrium (Y) are produced via neutron capture (ncapture). These elements reside in the mass range where there is uncertainty about the production mechanism at early time. The rapid n-capture process (r-process) was believed to be responsible for the production, but no study (Burris et al 2000, Gilroy et al 1988 and others) has been able to successfully use the r-process to reproduce the abundance signature for elements in this mass range for metal-poor halo stars. It has been suggested (Sneden and Cowan 2003) that there may be an undiscovered component to the rprocess. New abundance calculations for these elements have been conducted for a sample of metalpoor halo stars. Transition probabilities for Zr II from (Malcheva et al.2006) and for YII from (Hannaford et al.1982) were utilized in these calculations as well as new high quality observational data from the Keck telescope. The new laboratory and observational data resulted in improvement in the abundance determinations and uncertainty of the abundances.
Burris, D.; Jones, E.; and Lusk, J.
"Taking Another Look: Light n-Capture Element Abundances in Metal-Poor Halo Stars,"
Journal of the Arkansas Academy of Science: Vol. 62
, Article 8.
Available at: http://scholarworks.uark.edu/jaas/vol62/iss1/8