AAS 195th Meeting, January 2000
Session 50. Stellar Atmospheres
Display, Thursday, January 13, 2000, 9:20am-6:30pm, Grand Hall

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[50.09] The Iron Abundance in AV~304, a B0.5 Main Sequence Star in the Small Magellanic Cloud

G.J. Peters (USC), J.A. Grigsby (Ball Aerospace)

AV~304 is a sharp-lined B0.5V star in the Small Magellanic Cloud. We have determined the abundance of Fe using spectra obtained with HST/STIS and the Kurucz LTE model atmosphere/spectrum synthesis codes ATLAS9/SYNTHE. This is the first determination of the iron abundance in a star in an external galaxy directly from photospheric data. Following earlier analyses of ground-based data on the lighter elements in this star (Dufton, Fitzsimmons, & Howarth, 1990, ApJ, 362, L59 and Rolleston et al. 1993, A&A, 277, 10), we adopted a model of \rm Teff = 27,000~K, log~g = 4.0, and [M/H] = -0.5 for our study. Other input parameters used included \rm Vturb = 5~\rm km~s- 1, v~sin~i = 20~\rm km~s-1, and an instrumental broadening parameter of 13,000 corresponding to the resolving power of the STIS/G230M & G140M gratings. Twenty-two strong, relatively unblended, Fe~III lines between 1890--1970~Å\, yielded an Fe abundance of 6.7±0.2 or [Fe/H]~-1.0. Proportionally Fe appears to be even less abundant than the lighter elements in this star. This could indicate that there have been fewer Type Ia supernovae in the region of the SMC that AV~304 resides than one would expect. We present our analyses of the Fe lines and also those of other Fe group elements (Ti, V, Cr, Mn, Co, & Ni) and light elements in the spectral regions (1230--1400~Å\,, 1730--1810Å\,) that were observed. We appreciate support for this project from GO-06709-95A from the Space Telescope Science Institute.

The author(s) of this abstract have provided an email address for comments about the abstract: gjpeters@mucen.usc.edu

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