Boron in the small magellanic cloud: A novel test of light-element production

Hubble Space Telescope Space Telescope Imaging Spectrograph (STIS) observations of the B III resonance line at λ2066 have been obtained and analyzed for two Small Magellanic Cloud (SMC) B-type stars. While boron is not detected in either star, upper limits to the boron abundance are set, with 12 + log(B/H) ≤ 1.6 for both AV 304 and NGC 346-637. The upper limits are consistent with the relationship between boron and oxygen previously reported for Galactic disk stars. The SMC upper limits are discussed in light of that galaxy's star formation history, present oxygen abundance, and present cosmic-ray flux. The UV spectrum has also been used to determine the iron-group abundances in the SMC stars. For AV 304, [Fe/H] = -0.6 ± 0.2, from both an absolute and a differential analysis (with respect to the Galactic B-type star HD 36591). This is consistent with results from A-F supergiants in the SMC. A lower iron abundance is found for NGC 346-637, [Fe/H] = -1.0 ± 0.3, but this is in good agreement with the supergiant iron abundances in NGC 330, another young SMC cluster. We propose that NGC 346-637 might be an unrecognized binary, however, which complicates its spectral analysis.