Using standard 1D-LTE model atmosphere analysis , we provide an in-depth investigation of iron abundance as derived from neutral and singly ionization iron lines ( Fe I , II ) in nearby star clusters .
Specifically , we replicate the discrepancy regarding \Delta [ Fe/H ] , wherein the difference of Fe II - Fe I increases for stars of the same cluster with decreasing T _ { \mathrm { eff } } , reaching an astonishing 1.0 dex at T _ { \mathrm { eff } } \thicksim 4000 K. Previous studies have investigated this anomaly in the Pleiades and Hyades clusters with no concrete solution .
In this analysis , we probe two samples : 63 wide binary field stars where the primary star is of sun-like temperatures and the secondary is a K-dwarf , ranging from 4231 K \leq T _ { \mathrm { eff } } \leq 6453 K , and 33 Hyades stars of temperatures 4268 K \leq T _ { \mathrm { eff } } \leq 6072 K. Previous studies have found discrepancies on the order of 1.0 dex .
However , we find that these studies have neglected line-blending effects of certain Fe II lines , namely \lambda = { 4508.29 Å , 4993.34 Å , 5197.58 Å , 5325.55 Å , 5425.26 Å , 6456.38 Å } .
When these lines are removed from the line-list , we find \Delta [ Fe/H ] decreases to \thicksim 0.6 dex in the field binaries and \thicksim 0.3 dex in the Hyades .
The reason for this remaining trend is investigated by probing NLTE effects , as well as age and activity considerations using Ca II H+K emission and Li absorption , but these results appear to be small to negligible .