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 °A 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 ǫ(B)= +0.01 ± 0.20. This value is con- sistent with the linear relation of slope 1.0 between log ǫ(BLTE) and [Fe/H] found for 10 halo and disk stars by Duncan et al. (1997). Using the NLTE correction of Kisel- man & Carlsson (1996), the NLTE boron abundance is log ǫ(B)= +0.93 ± 0.20. This is also consistent with the NLTE relation determined by Duncan et al. (1997) where the slope of log ǫ(BNLTE) 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.