title: Neutron-Capture Element Abundances in the Globular Cluster M15.
abstract: High-resolution, high signal-to-noise ratio, blue-violet spectra of three red giant branch tip stars in M15 have been obtained with the Keck I High-Resolution Echelle Spectrograph. These spectra have been analyzed to determine the abundances of several neutron-capture elements, including the radioactive chronometer element thorium. There are two principal results of this study. First, the abundances of the heavier (Z>/=56) elements for each of the three stars is well matched by a scaled solar system r-process abundance distribution. Second, a weighted mean-observed Th/Eu ratio for the stars implies an age for the neutron-capture material in M15 stars of 14+/-3 Gyr, in reasonable agreement with other recent age estimates for Galactic globular clusters.
authors.initials: C
authors.lastname: Sneden
authors.initials: J
authors.lastname: Johnson
authors.initials: RP
authors.lastname: Kraft
authors.initials: GH
authors.lastname: Smith
authors.initials: JJ
authors.lastname: Cowan
authors.initials: MS
authors.lastname: Bolte