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C. R. Cowley (University of Michigan), G. M. Wahlgren (Lund University)
Until recently, bromine (Z = 35) was unidentified in stellar spectra. Castelli and Hubrig (A&A, 425, 263, 2004) identified two weak lines of Br II in the HgMn star HR 7143 (HD 175640), and we now report a bromine abundance for the He-3 star 3 Cen A based on three lines with known f-values. An additional six lines may be attributed to Br II in our spectrum. We believe this is only the second case of the identification of the spectrum of this ion in a star. In an unpublished study, W. P. Bidelman has identified Br I in HD 101065.
While 3 Cen A is a reasonably well-studied star, no abundance had been reported for a second odd-Z element, vanadium (Z = 23). Strong V II lines of Multiplet No. 1 lie in the region 3093-3145 Å, not typically included in older stellar spectra.
We have used an ESO spectrum from the UVES-POP archive, (Bagnulo, et al. ESO Messenger 114, 10, 2003). The analysis is based on an Atlas model atmosphere computed with Teff = 17500K and log(g) = 3.8 (cf. Wahlgren and Hubrig A&A, 418, 1073, 2004) and two approaches to abundance determination, the matching of equivalent widths and the direct fitting of line profiles.We find an excess of bromine of ca. 3.0 dex and of vanadium of 1.4 dex, both with respect to the solar abundances. These results, taken with previous work, strengthen the overall agreement with the expected abundance pattern. According to the theory of radiative-driven diffusion, odd-Z elements are typically enhanced with respect to their even-Z neighbors.
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Bulletin of the American Astronomical Society, 37 #2
© 2005. The American Astronomical Soceity.