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EP: Fachverband Extraterrestrische Physik
EP 2: Astrophysics II
EP 2.4: Talk
Monday, March 16, 2026, 17:00–17:15, KH 01.019
R-process nucleosynthesis in collapsar accretion disk outflows and cosmic chemical evolution — •Aman Agarwal1 and Daniel Siegel1,2 — 1Institute of Physics, University of Greifswald, D-17489 Greifswald, Germany — 2Department of Physics, University of Guelph, Guelph, Ontario, Canada, N1G 2W1
The collapse of rapidly rotating massive stars (“collapsars”; MZAMS 40 M⊙ at birth) are leading models for long gamma-ray burst (GRBs) central engines and promising sources of neutron-rich environments for r-process nucleosynthesis. Here, we extend the range of collapsars and explore collapsar accretion disk flows around black holes of mass M•=3−3000 M⊙ using long-term, three-dimensional general-relativistic magnetohydrodynamics simulations with weak interactions and find that the accretion flows neutronize above an “ignition” accretion rate Ṁign. We present remarkable agreement between our simulations and the analytic result Ṁign∝ α5/3M•4/3 with αeff being the effective Shakura-Sunyaev viscosity. We demonstrate by semi-analytical modeling that stellar models of ∼ 250−105 M⊙ mass can give rise to BHs of M•∼ 30−1000 M⊙ accreting at Ṁ Ṁign, yielding ∼ 10−100 M⊙ of r-process elements per event. We highlight their potential as multi-messenger sources of optical/IR transients (“super-kilonovae”) and gravitational waves (GWs) for third-generation (3G) GW detectors. Using a one-zone chemical evolution model and a projection of future 3G GW and abundance observations, we demonstrate a correlation technique to infer the percentage contribution of multiple sources to galactic and cosmic r-process enrichment.
Keywords: r-process nucleosynthesis; collapsars; black holes; accretion disks; multi-messenger astrophysics