The purpose of this work is to resume investigation of Galactic thin disk dating using nucleocosmochronology with Th/Eu stellar abundance ratios , a theme absent from the literature since 1990 .
[ Th/Eu ] abundance ratios for a sample of 20 disk dwarfs/subgiants of F5 to G8 spectral type with -0.8 \leq \mathrm { [ Fe / H ] } \leq + 0.3 , determined in the first paper of this series , were adopted for this analysis .
We developed a Galactic chemical evolution model that includes the effect of refuse , which are composed of stellar remnants ( white dwarfs , neutron stars and black holes ) and low-mass stellar formation residues ( terrestrial planets , comets , etc .
) , contributing to a better fit to observational constraints .
Two Galactic disk ages were estimated , by comparing literature data on Th/Eu production and solar abundance ratios to the model ( 8.7 ^ { +5.8 } _ { -4.1 } ~ { } \mbox { Gyr } ) , and by comparing [ Th/Eu ] vs. [ Fe/H ] curves from the model to our stellar abundance ratio data ( ( 8.2 \pm 1.9 ) ~ { } \mbox { Gyr } ) , yielding the final , average value ( 8.3 \pm 1.8 ) ~ { } \mbox { Gyr } .
This is the first Galactic disk age determined via Th/Eu nucleocosmochronology , and corroborates the most recent white dwarf ages determined via cooling sequence calculations , which indicate a low age ( \lesssim 10 \mbox { Gyr } ) for the disk .