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Session 103 - Cool Stars.
Display session, Thursday, January 18
North Banquet Hall, Convention Center
We have detected the very heavy elements osmium, platinum and lead in the metal-poor ([Fe/H] = -1.7) Galactic halo star HD 126238, from spectra acquired with the Goddard High-Resolution Spectrograph (GHRS) of the Hubble Space Telescope (HST). These are the first such detections of these elements in a very metal-poor star. Os and Pt are synthesized predominantly in the rapid neutron capture process (i.e. the r-process). Within the error limits, the elemental abundances of Os and Pt are consistent with solar system abundances scaled to the metallicity of HD 126238. Combining the Pt and Os abundances with those of lighter neutron-capture elements obtained from ground-based spectra allows us to map out, for the first time, the operation of r-process nucleosynthesis for elements spanning the range from Ba (Z=56) to Pt (Z=78) in the progenitor (or progenitors) of this halo star. The newly determined Pb abundance, predominantly produced in the slow neutron capture process (i.e. the s-process) in solar material, can be best explained with a mixture of r- and s-process contributions.
Program listing for Thursday