Elemental Abundances of Ultraheavy Cosmic Rays

Abstract

The elemental composition of the cosmic-ray source is different from that which has been generally taken as the composition of the solar system. No general enrichment of products of either r-process or s-process nucleosynthesis accounts for the differences over the entire range of ultraheavy (Z > 30) elements; specific determination of nucleosynthetic contributions to the differences depends upon an understanding of the nature of any acceleration fractionation. Comparison between the cosmic-ray source abundances and the abundances of C1 and C2 chondritic meteorites suggests the possibility that differences between the cosmic-ray source and the “standard (C1) solar system” may not be due to acceleration fractionation of the cosmic rays, but may be due instead to a fractionation of the C1 abundances with respect to the interstellar abundances.