Multiple sources or late injection of short-lived r-nuclides in the early solar system?

Abstract

Comparisons between the predicted abundances of short-lived r-nuclides (¹⁰⁷Pd, ¹²⁹I, ¹⁸²Hf, and ²⁴⁴Pu) in the interstellar medium (ISM) and the observed abundances in the early solar system (ESS) conclusively showed that these nuclides cannot simply be derived from galactic chemical evolution (GCE) if synthesized in a unique stellar environment. It was thus suggested that two different types of stars were responsible for the production of light and heavy r-nuclides. Here, new constraints on the ²⁴⁴Pu/²³⁸U production ratio are used in an open nonlinear GCE model. It is shown that the two r-process scenario cannot explain the low abundance of ²⁴⁴Pu in the ESS and that this requires either than actinides be produced at an additional site (A-events) or more likely, that ¹²⁹I and ²⁴⁴Pu be inherited from GCE and ¹⁰⁷Pd and ¹⁸²Hf be injected in the ESS by the explosion of a nearby supernova. © 2005 Elsevier B.V. All rights reserved.