Injection of Short-Lived Radionuclides into the Early Solar System from a Faint Supernova with Mixing Fallback

Several short-lived radionuclides (SLRs), some of which should have formed just prior to or soon after the solar system formation, were present in the early solar system. Stellar nucleosynthesis has been proposed as the mechanism for the production of SLRs in the solar system, but no appropriate stellar source has been found that explains the abundances of all solar system SLRs. In this study, we propose a faint supernova with mixing and fallback as a stellar source of SLRs with mean lives of <5 Myr (²⁶Al,⁴¹Ca,⁵³Mn, and ⁶⁰Fe) in the solar system. In such a supernova, the inner region of the exploding star experiences mixing, a small fraction of mixed materials is ejected, and the rest undergoes fallback onto the core. The modeled SLR abundances agree well with their solar system abundances if mixing fallback occurs within the C/O-burning layer. In some cases, the initial solar system abundances of the SLRs can be reproduced within a factor of 2. The dilution factor of supernova ejecta to the solar system materials is ~10⁻⁴, and the time interval between the supernova explosion and the formation of the oldest solid materials in the solar system is ~1 Myr. If the dilution occurred due to spherically symmetric expansion, a faint supernova should have occurred near the solar system-forming region in a star cluster.