Boron Abundances in Early B Stars: Results from the B III Resonance Line in IUE Data

Abstract

We have used archival International Ultraviolet Explorer high-dispersion SWP spectra to study the B III resonance line at 2065.8 Å in 44 early B stars. We find a median boron abundance about half that of solar system meteoritic material, consistent with the values found from previous studies of boron in early B stars. About one-third of the stars studied appear to have boron abundances that are a factor of 4 or more lower than this median. Many of these are stars with enhanced nitrogen abundances, confirming the belief that deep envelope mixing can occur in main-sequence B stars. A few stars with low boron abundances have normal N/C ratios. It is unclear whether all of these can be explained as stars where mixing depleted the boron but did not go deep enough to bring CN-processed material to the surface or if some stars were actually formed with an unusually low boron abundance.