Galactic Chemical Evolution of Radioactive Isotopes with an s-process Contribution

1,2,8Thomas C. L. Trueman,1,3,4,8Benoit Côté,1,8Andrés Yagüe López,1,8Jacqueline den Hartogh,1,2,4,8Marco Pignatari,1,5Benjámin Soós,6,7Amanda I. Karakas,1,5,6Maria Lugaro
The Astrophysical Journal 924, 10 Open Access Link to Article [DOI 10.3847/1538-4357/ac31b0]
1Konkoly Observatory, Research Centre for Astronomy and Earth Sciences, Eötvös Loránd Research Network, Konkoly Thege Miklós út 15-17, H-1121 Budapest, Hungary; thomas.trueman@csfk.mta.hu
2E.A. Milne Centre for Astrophysics, Department of Physics & Mathematics, University of Hull, HU6 7RX, UK
3Department of Physics and Astronomy, University of Victoria, Victoria, BC, V8W 2Y2, Canada
4Joint Institute for Nuclear Astrophysics—Center for the Evolution of the Elements, USA

5ELTE Eötvös Loránd University, Institute of Physics, Budapest 1117, Pázmány Péter sétány 1/A, Hungary
6School of Physics and Astronomy, Monash University, VIC 3800, Australia
7ARC Centre of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D), Australia
8NuGrid Collaboration http://nugridstars.org.

Analysis of inclusions in primitive meteorites reveals that several short-lived radionuclides (SLRs) with half-lives of 0.1–100 Myr existed in the early solar system (ESS). We investigate the ESS origin of 107Pd, 135Cs, and 182Hf, which are produced by slow neutron captures (the s-process) in asymptotic giant branch (AGB) stars. We modeled the Galactic abundances of these SLRs using the OMEGA+ galactic chemical evolution (GCE) code and two sets of mass- and metallicity-dependent AGB nucleosynthesis yields (Monash and FRUITY). Depending on the ratio of the mean-life τ of the SLR to the average length of time between the formations of AGB progenitors γ, we calculate timescales relevant for the birth of the Sun. If τ/γ ≳ 2, we predict self-consistent isolation times between 9 and 26 Myr by decaying the GCE predicted 107Pd/108Pd, 135Cs/133Cs, and 182Hf/180Hf ratios to their respective ESS ratios. The predicted 107Pd/182Hf ratio indicates that our GCE models are missing 9%–73% of 107Pd and 108Pd in the ESS. This missing component may have come from AGB stars of higher metallicity than those that contributed to the ESS in our GCE code. If τ/γ ≲ 0.3, we calculate instead the time (TLE) from the last nucleosynthesis event that added the SLRs into the presolar matter to the formation of the oldest solids in the ESS. For the 2 MZ = 0.01 Monash model we find a self-consistent solution of TLE = 25.5 Myr.

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