Oxygen abundances of 67 dwarf stars in the metallicity range -1.6 < \mathrm { [ Fe / H ] } < -0.4 are derived from a non-LTE analysis of the 777 nm O i triplet lines .
These stars have precise atmospheric parameters measured by Nissen and Schuster , who find that they separate into three groups based on their kinematics and \alpha -element ( Mg , Si , Ca , Ti ) abundances : thick-disk , high- \alpha halo , and low- \alpha halo .
We find the oxygen abundance trends of thick-disk and high- \alpha halo stars very similar .
The low- \alpha stars show a larger star-to-star scatter in [ O/Fe ] at a given [ Fe/H ] and have systematically lower oxygen abundances compared to the other two groups .
Thus , we find the behavior of oxygen abundances in these groups of stars similar to that of the \alpha elements .
We use previously published oxygen abundance data of disk and very metal-poor halo stars to present an overall view ( -2.3 < \mathrm { [ Fe / H ] } < +0.3 ) of oxygen abundance trends of stars in the solar neighborhood .
Two field halo dwarf stars stand out in their O and Na abundances .
Both G53-41 and G150-40 have very low oxygen and very high sodium abundances , which are key signatures of the abundance anomalies observed in globular cluster ( GC ) stars .
Therefore , they are likely field halo stars born in GCs .
If true , we estimate that at least 3 \pm 2 % of the local field metal-poor star population was born in GCs .