AAS Meeting #193 - Austin, Texas, January 1999
Session 45. Spectral Observations of Stars
Display, Thursday, January 7, 1999, 9:20am-6:30pm, Exhibits Hall 1

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[45.01] Another r-Process-Enriched Halo Star: HD 115444

J. Westin, C. Sneden (U. Texas), B. Gustafsson, B. Edvardsson (Uppsala U.), J.J. Cowan (U. Oklahoma)

A new high resolution very high signal to noise spectrum has been obtained for the metal-poor giant star HD 115444, first examined in detail by Griffin et al. (1982, MNRAS, 198, 637). Our new spectrum was gathered with the High-Resolution Echelle Spectrometer of the McDonald Observatory 2.7m Telescope. We have performed a model atmosphere analysis and line identification, emphasizing the neutron-capture elements; 20 elements with Z>30 have been identified in the HD~115444 spectrum. The overall metallicity was found to be [Fe/H] = --3.0. The abundances of the light and iron-peak elements show the same pattern as other very metal-poor stars (e.g. overdeficiencies of Mn and Cr, overabundances of Co).

The initial synthetic spectrum analyses reveal substantial overabundances of all neutron-capture elements with Z\geq56 (Ba and beyond). Moreover, the abundance pattern is clearly consistent with production dominated by r-process nucleosynthesis (with little contribution from the s-process), just like that also found in the metal-poor giant star CS~22892-052 (Sneden et al., 1996, ApJ, 467, 819). To illustrate this, in HD~115444 we find [Ba/Eu]~= --0.73, while in CS~22892-052, this ratio is --0.79.

Thus HD 115444 becomes the second clear example of a very metal-poor yet r-process-rich halo giant. With (for example) [Eu/Fe]~q+0.9, HD~115444 is a moderate version of CS~22892-052 (which has [Eu/Fe]~q+1.7).

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