Boron in the very metal-poor star BD -13 3442

The Goddard High Resolution Spectrograph (GHRS) of the Hubble Space Telescope (HST) has been used to observe the boron 2500 Angstroms region of BD -13 3442. At a metallicity of [Fe/H]=-3.00 this is the most metal-poor star ever observed for B. Nearly 26 hours of exposure time resulted in a detection. Spectrum synthesis using the latest Kurucz model atmospheres yields an LTE boron abundance of log epsilon (B)= +0.01+/-0.20. This value is consistent with the linear relation of slope ~ 1.0 between log epsilon (B_LTE) and [Fe/H] found for 10 halo and disk stars by Duncan et al. (1997). Using the NLTE correction of Kiselman & Carlsson (1996), the NLTE boron abundance is log epsilon (B)= +0.93+/-0.20. This is also consistent with the NLTE relation determined by Duncan et al. (1997) where the slope of log epsilon (B_NLTE) vs. [Fe/H] is ~ 0.7. These data support a model in which most production of B and Be comes from the spallation of energetic C and O nuclei onto protons and He nuclei, probably in the vicinity of massive supernovae in star-forming regions, rather than the spallation of cosmic ray protons and alpha particles onto CNO nuclei in the general interstellar medium. This research was based on observations obtained with the NASA/ESA Hubble Space Telescope through the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555