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

Abstract

Several short-lived radionuclides (SLRs) were present in the early solar system, some of which should have formed just prior to or soon after the solar system formation. Stellar nucleosynthesis has been proposed as the mechanism for production of SLRs in the solar system, but no appropriate stellar source has been found to explain 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 ( 26 Al, 41 Ca, 53 Mn, and 60 Fe) 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 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 nearby the solar system forming region in a star cluster.

Triggering Collapse of the Presolar Dense Cloud Core and Injecting Short-lived Radioisotopes with a Shock Wave. V. Nonisothermal Collapse Regime

“…Given that models L and J led to f i ≈ 0.045, and taking β ≈ 0.01, we get D ≈ 1.4 × 10 −4 . This dilution factor is on the lower end of cosmochemical estimates of D in the range of 1.3 × 10 −4 to 1.9 × 10 −3 for pre-supernova stars with masses of 25 M ⊙ and 20 M ⊙ , respectively (Takigawa et al 2008). …”

“…For a 25 M ⊙ pre-supernova star and a neutron star remnant, then, at most ≈ 7.2 × 10 −4 M ⊙ of SN-derived matter can be injected into the target cloud, based on geometric dilution alone, assuming a nominal distance of 5 pc. Boss & Keiser (2014) noted that geometric dilution is not the dilution factor used their previous studies and in cosmochemical estimates of initial SLRI abundances (e.g., Takigawa et al 2008). This latter dilution factor D is defined as the ratio of the amount of mass derived from the supernova to the amount of mass derived from the target cloud.…”

Tidally Induced Brown Dwarf and Planet Formation in Circumstellar Disks

“…This mechanism may even work in typical protoplanetary disks and is a subject of our ongoing research. According to solar system architecture (Heller 1993;Eggers et al 1997;Kenyon & Bromley 2004) and radionuclide evidence (Takigawa et al 2008;Sahijpal & Gupta 2009;Gaidos et al 2009;Gounelle & Meibom 2008, however, disagree), the highly probable origin of our Sun in a large star-forming region further emphasizes the importance of such scenarios.…”

SUPERNOVA NEUTRINO NUCLEOSYNTHESIS OF THE RADIOACTIVE 92 Nb OBSERVED IN PRIMITIVE METEORITES

“…The material ejected from the last SN will be diluted and then mixed with the collapsing protosolar cloud. Assuming that the ejected material is well mixed with the pre-existing material in the protosolar cloud, the abundance ratio will be (Takigawa et al 2008) …”

“…One of the major possible sources of SLRs involves a SN as the trigger for the collapse of the pre-solar cloud (Huss et al 2009). An initial solar abundance of 60 Fe has also been reported and a late input, ejecta from a nearby SN into the proto-planetary disk or the molecular cloud after the start of the collapse, was proposed (Ouellette et al 2007;Takigawa et al 2008). Recently, however, Tang & Dauphas (2012) showed that the abundance of 60 Fe can be explained by the accumulated background of the Galaxy.…”