Oxygen abundances are derived in a sample of 13 field F and G dwarfs or subgiants with metallicities in the range of -0.75 \leq [ Fe/H ] \leq +0.15 .
This is the same sample of stars for which boron abundances have been derived earlier from archived spectra obtained with the Hubble Space Telescope .
Only the weak [ O I ] \lambda 6300Å and O I \lambda 6157Å and \lambda 6158Å lines have been used to determine O abundances .
It is argued that , over the range of temperature and metallicity spanned by the program stars , these [ O I ] and O I lines provide accurate oxygen abundances , largely free from non-LTE or 1D model atmosphere effects .
The results for oxygen are combined with the boron abundances published previously to define a boron versus oxygen abundance for field disk stars : the relation log ( B/H ) + 12 .
= log \epsilon ( B ) = 1.39 \pm 0.08log \epsilon ( O ) - 9.62 \pm 1.38 is obtained .
The slope of m _ { BO } =1.39 ( in log-log abundance by number coordinates ) indicates that , in the disk , the abundance of B , relative to O , is intermediate between primary and secondary production ( hybrid behavior ) .
The slope found here for log \epsilon ( B ) versus log \epsilon ( O ) is identical , within the uncertainties , to that found by previous investigators for log \epsilon ( Be ) versus log \epsilon ( O ) , where m _ { BeO } =1.45 .
The two relations of B and Be versus O result in essentially solar B/Be ratios for field disk stats .
A comparison of the results here for B–O in the disk to B–O in the halo ( with B abundances taken from the literature ) reveals that , if [ O/Fe ] in the halo is nearly constant , or undergoes only a gentle increase with decreasing [ Fe/H ] , then boron behaves as a primary element relative to oxygen .
In such a case , there is a transition from N ( B ) \alpha N ( O ) in the halo , to N ( B ) \alpha N ( O ) ^ { 1.4 } in the disk .
On the other hand , if [ O/Fe ] increases substantially in the halo ( such that [ O/Fe ] \alpha -0.4 [ Fe/H ] ) , as suggested by some studies of the 3100-3200Å electronic OH lines , then there is no significant difference between the behavior of B–O in the halo compared to the disk ( i.e .
N ( B ) \alpha N ( O ) ^ { 1.4 } ) .