The Abundances of Ultraheavy Elements in the Cosmjc Radiation

Analysis of a -new, higher resolution data set from the Heavy Nuclei Experiment on the HEA0-3 spacecraft has yielded the cosmic ray abundances relative to iron of oddeven element pairs with atomic number, Z, in the range 33sZs60. The abundances are consistent 'Yith a solar-system source provided an allowance is made for a source fraetionation based on first ionization potential (FIP). However, extending this analysis· to element groups with Z>60, we find enhancements of the Pt group (74SZS80) abundance relative to the solar system and a corresponding increase in the largely secondary nuclei in the range 62sZS73, in agreement with recent Ariel-6 results. These abundances suggest an enhancement of the r-process contribution to the source of the Z > 60 nuclei.