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