Abundances of neutron capture elements in metal-poor dwarfs. I - Yttrium and zirconium

The yttrium and zirconium abundances are determined in a sample of 20 metal-poor stars on the basis of high resolution, high SNR spectra. Significant differences between the behaviors of these two neighboring elements are found, zirconium being less deficient than yttrium in Population II stars. Moreover, there is a genuine cosmic scatter in the abundances of these two elements relative to iron, of the order of 20 percent. The scatter is lower when these elements are compared to titanium, which might indicate that a significant fraction of the lighter neutron-capture elements are produced in massive stars.