Abundances of actinides and short-lived nonactinides in the interstellar medium: Diverse supernova sources for the r-processes

Abundances of Pu-244, U-235, U-238, and Th-232, in the early solar system are about those expected for uniform production over most of galactic history. The inferred abundance of Hf-182 is also compatible with this model. We here associate production of Hf-182 With the same r-process SN sources that produce actinides (SNACS). This requires that r-process nucleosynthesis in SNACS took place rather uniformly over the age of the galaxy until similar to 10(7) yr prior to solar system formation. The low abundance of Pd-107 and I-129 in the early solar system indicates that SNACS cannot produce these nuclei at the high yields expected from standard r-process models. We propose that there are distinctive SN sources for different r-process nuclei with a sharp distinction in different SN contributions below and above A similar to 140. Abundances in stars with very low metallicities will vary depending on the type of SN contributing to the local region of star formation. A time scale of similar to 10(7) yr is much shorter than the 10(8) yr time usually associated with processes in the galaxy and with the last time of r-process injection accounting for I-129, but may be compatible with the rate of SN occurrence. The hypothesis of a nearby SN polluting the protosolar nebula is critically discussed.