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 \lesssim [ Fe/H ] \lesssim + 0.1 , and most of them are dwarfs .
The plane-parallel LTE MAFAGS-OS model atmosphere was adopted , and the spectral synthesis method was used to derive the Pd and Ag abundances from Pd i \lambda 3404 Å and Ag i \lambda 3280/3382 Å 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 .