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W. V. Dixon (JHU), T. M. Brown (STScI), W. B. Landsman (SSAI/NASA/GSFC)
Only two hot post-asymptotic giant branch (PAGB) stars in globular clusters, Barnard 29 in M13 and ROA 5701 in Omega Cen, have well-determined iron abundances, and in both cases [Fe/H] is more than 0.5 dex below the cluster mean. The stars apparently lost a significant fraction of their photospheric iron while on the AGB, perhaps through the selective condensation of iron onto dust grains. To determine the frequency of iron depletion among cluster PAGB stars and to test scenarios for this depletion, we have begun a project to re-analyze archival spectra of cluster PAGB stars obtained with the Hopkins Ultraviolet Telescope. (HUT flew on the Astro-1 and 2 Space Shuttle missions in 1990 and 1995. Its first-order sensitivity ranged from 820 to 1840 Å\ with a resolution of about 3 Å.) Using state-of-the-art non-LTE line-blanketed stellar atmosphere models, we determine the effective temperature, surface gravity and iron abundance of each star. In this poster, we present preliminary results for the stars BS in 47 Tuc, vZ 1128 in M3, and UV5 in NGC 1851.
This work is supported by NASA grant NAG 5-10916.
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Bulletin of the American Astronomical Society, 35#5
© 2003. The American Astronomical Soceity.