Astronomy and Astrophysics, volume 579A, 8-8 (2015/7-1)
Palladium and silver abundances in stars with [Fe/H] > -2.6.
WU X., WANG L., SHI J., ZHAO G. and GRUPP F.
Abstract (from CDS):
Palladium (Pd) and silver (Ag) are the key elements for probing the weak component in the rapid neutron-capture process (r-process) of stellar nucleosynthesis. We performed a detailed analysis of the high-resolution and high signal-to-noise ratio near-UV spectra from the archive of HIRES on the Keck Telescope, UVES on the VLT, and HDS on the Subaru Telescope, to determine the Pd and Ag abundances of 95 stars. This sample covers a wide metallicity range with -2.6≲[Fe/H]≲+0.1, and most of them are dwarfs. The plane-parallel local thermodynamic equilibrium MAFAGS-OS model atmosphere was adopted, and the spectral synthesis method was used to derive the Pd and Ag abundances from PdI λ3404Å and AgI λ3280/3382Å lines. We found that both elements are enhanced in metal-poor stars, and their ratios to iron show flat trends at -0.6<[Fe/H]<+0.1. The abundance ratios of [Ag/H] and [Pd/H] are well correlated over the whole abundance range. This implies that Pd and Ag have similar formation mechanisms during the Galactic evolution.
stars: abundances - stars: Population II - Galaxy: evolution