AAS 202nd Meeting, May 2003
Session 32 Stellar Atmospheres and Circumstellar Material
Poster, Tuesday, May 27, 2003, 10:00am-6:30pm, West Exhbit Hall

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[32.10] High Resolution Optical Spectroscopy of the Hg-Mn Star HR7143

D. J. Bord (UMich-Dearborn), C. R. Cowley (UMich-Ann Arbor), S. Hubrig (ESO), W. P. Bidelman (CWRU)

HR7143 (HD175640) is a sharp-lined Hg-Mn star which, despite much study, still appears to harbor some unusual spectroscopic characteristics. Based on high resolution (>80,000), high signal-to-noise (>300) data covering the range \lambda\lambda3050-6750 Å obtained with the VLT echelle spectrograph at ESO, we have carried out wavelength coincidence statistics (WCS) analyses based on 3134 measured lines. In addition to the common element identifications expected in a typical Hg-Mn star, we find very strong statistical evidence (at the 5\sigma level or greater) to support the presence O I, S II, Pd I, and Xe II. Our examination of individual spectral features has provided corroboration for these identifications, each of which presents a fresh challenge to our understanding of the spectrum of this object. For example, although singly ionized palladium has been identified in several chemically peculiar stars, including \chi Lupi, HR7143 seems to be the only star of this type, save HR465, in which Pd I has been reported, and its presence in a star as hot as this may signal a large overabundance of this element. The strong appearance of xenon in an object that has been shown to be deficient in neon by nearly an order of magnitude with respect to the Sun is also intriguing. In addition to presenting the full details of our WCS study, we will elaborate the implications of the presence in this star of the four species noted above and, for some, derive abundances based on measured equivalent widths using an LTE model atmosphere with Teff = 12,000 K and log g = 3.95. Further information concerning the spectrum of this star and our progress in its analysis may be obtained at: http://www.astro.lsa.umich.edu/users/cowley/AAS0503Don/.

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