Limits on the Boron Isotopic Ratio in HD 76932

Data in the 2090 A B region of HD 76932 have been obtained at high S/N usingthe HST GHRS echelle at a resolution of 90,000. This wavelength region has beenpreviously identified as a likely candidate for observing the B11/B10 isotopicsplitting. The observations do not match a calculated line profile extremely well at anyabundance for any isotopic ratio. If the B abundance previously determined fromobservations at 2500 A is assumed, the calculated line profile is too weak,indicating a possible blending line. Assuming that the absorption at 2090 A isentirely due to boron, the best-fit total B abundance is higher than butconsistent with that obtained at 2500 A, and the best-fit isotopic ratio(B11/B10) is in the range ~10:1 to ~4:1. If the absorption is not entirely dueto B and there is an unknown blend, the best-fit isotopic ratio may be closerto 1:1. Future observations of a similar metal-poor star known to haveunusually low B should allow us to distinguish between these two possibilities.The constraints that can be placed on the isotopic ratio based on comparisonswith similar observations of HD 102870 and HD 61421 (Procyon) are alsodiscussed.Comment: Accepted for Nov 1998 Ap