Göttingen 2025 – scientific programme

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EP: Fachverband Extraterrestrische Physik

EP 15: Astrophysics III

EP 15.4: Talk

Friday, April 4, 2025, 14:30–14:45, ZHG101

Ignition of weak interactions and r-process outflows in massive, ‘super-collapsar’ accretion disks — •Aman Agarwal¹ and Daniel Siegel^1,2 — ¹Institute of Physics, University of Greifswald, D-17489 Greifswald, Germany — ²Department of Physics, University of Guelph, Guelph, Ontario, Canada, N1G 2W1

The core collapse of rapidly rotating massive (∼ 10 M_⊙) stars (“collapsars”) and the resulting hyperaccreting black holes represent a leading model for the central engines of long-duration gamma-ray bursts (GRBs) and promising sources of neutron-rich plasma outflows for r-process nucleosynthesis. We perform three-dimensional general-relativistic magnetohydrodynamics simulations to explore the neutronization of accretion flows from progenitors with masses above the pair-instability mass gap to the regime of massive PopIII stars (black-hole mass range M_•∼ 80−1000 M_⊙). We find that neutron-rich accretion flows develop above an “ignition” accretion rate Ṁ_ign, which, in good agreement with analytical estimates, scales as Ṁ_ign ∝ M_•^4/3α_eff^5/3 up to M_• ∼ 1000 M_⊙, with α_eff being the effective Shakura-Sunyaev disk viscosity. We discuss the implications of very early r-process enrichment through such astrophysical events in the light of recent detections of massive stars by the James Webb Space Telescope and reflect upon their potential as multi-messenger sources of both electromagnetic (“super-kilonovae”) and gravitational waves for third-generation gravitational-wave detectors.

Keywords: r-process nucleosynthesis; collapsars; black-holes; multi-messenger; Pop III stars