We investigated the copper abundances for 64 late-type stars in the Galactic disk and halo with effective temperatures from 5400 K to 6700 K and [ Fe/H ] from -1.88 to -0.17 .
For the first time , the copper abundances are derived using both local thermodynamic equilibrium ( LTE ) and non-local thermodynamic equilibrium ( non-LTE ) calculations .
High resolution ( R > 40 , 000 ) , high signal-to-noise ratio ( S / N > 100 ) spectra from the FOCES spectrograph are used .
The atmospheric models are calculated based on the MAFAGS opacity sampling code .
All the abundances are derived using the spectrum synthesis methods .
Our results indicate that the non-LTE effects of copper are important for metal-poor stars , showing a departure of \sim 0.17 dex at the metallicity \sim - 1.5 .
We also find that the copper abundances derived from non-LTE calculations are enhanced compared with those from LTE .
The enhancements show clear dependence on the metallicity , which gradually increase with decreasing [ Fe/H ] for our program stars , leading to a flatter distribution of [ Cu/Fe ] with [ Fe/H ] than previous work .
There is a hint that the thick- and thin-disk stars have different behaviors in [ Cu/Fe ] , and a bending for disk stars may exist .