Boron in the small magellanic cloud : a novel test of light element formation
I have examined HST STIS observations of the BIII resonance line at 2066 A for two SMC B-stars as a test of cosmic ray spallation as the production of boron. These stars, A V304 and NCG346-637, have unergone previous optical analysis, and do not show signs of mixing or mass loss (signaled by a surface enrichment of N), which can destroy the fragile boron atom. The abundance of the seed nuclei, oxygen, is well known and the same from location to location within the SMC, so the boron abundance for the entire galaxy. If B scales quadratically with O, as is predicted by GCR spallation, then based on an observed SMC O abundance of -0.7 relative to solar, we can make a simple prediction that boron will be underabundant by 1̃.4 dex, or 12 +log (B/H ̲1̃.0. However, if B scales linearly, we expect boron to be underabundant by 0.7 dex only. Also, recognizing that the SMC cosmic ray flux is 1/5 of that in the galaxy, then we might expect B production to be lower int he SMC overall. Unfortunately, the S/N of the data appears ot be liess than expected, and I find an upper limit on the boron abundance of log (B/H) + 12.0 dex=2.0 for each star. Thus, it is not possible to distinguish between the formation and destruction mechanisms of B, but I shall discuss these fully in the paper
Manuscript, English, 2001