Turbulent mixing of r-process elements in the Milky Way

Abstract

We study turbulent gas diffusion affects on $r$-process abundances in Milky Way stars, by a combination of an analytical approach and a Monte Carlo simulation. Higher $r$-process event rates and faster diffusion, lead to more efficient mixing corresponding to a reduced scatter of $r$-process abundances and causing $r$-process enriched stars to start appearing at lower metallicities. We use three independent observations to constrain the model parameters: (i) the scatter of radioactively stable $r$-process element abundances, (ii) the largest $r$-process enrichment values observed in any solar neighborhood stars and (iii) the isotope abundance ratios of different radioactive $r$-process elements (${}^{244}$Pu/${}^{238}$U and ${}^{247}$Cm/${}^{238}$U) at the early solar system as compared to their formation. Our results indicate that the Galactic $r$-process rate and the diffusion coefficient are respectively $r<4\times 10^{-5}\mbox{ yr}^{-1}, D>0.1 \mbox{ kpc}^2\mbox{Gyr}^{-1}$ ($r<4\times 10^{-6}\mbox{ yr}^{-1}, D>0.5 \mbox{ kpc}^2\mbox{Gyr}^{-1}$ for collapsars or similarly prolific $r$-process sources) with allowed values satisfying an approximate anti-correlation such that $D\approx r^{-2/3}$, implying that the time between two $r$-process events that enrich the same location in the Galaxy, is $τ_{\rm mix}\approx 100-200\mbox{ Myr}$. This suggests that a fraction of $\sim 0.8$ ($\sim 0.5$) of the observed ${}^{247}$Cm (${}^{244}$Pu) abundance is dominated by one $r$-process event in the early solar system. Radioactively stable element abundances are dominated by contributions from $\sim 10$ different events in the early solar system. For metal poor stars (with [Fe/H]$\lesssim -2$), their $r$-process abundances are dominated by either a single or several events, depending on the star formation history.

11 pages, 9 figures, accepted for publication in MNRAS

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Cited by in corpus (21)

• On the formation of GW190814
• 129I and 247Cm in Meteorites Constrain the Last Astrophysical Source of Solar r-process Elements
• Neutron star mergers as the astrophysical site of the r-process in the Milky Way and its satellite galaxies
• r-Process Radioisotopes from Near-Earth Supernovae and Kilonovae
• Highly r-process enhanced stars in ultra-faint dwarf galaxies
• Common envelope jets supernova r-process yields can reproduce $[Eu/Fe]$ abundance evolution in the Galaxy
• The interplay between feedback, accretion, transport and winds in setting gas-phase metal distribution in galaxies
• High-temperature ${}^{205}$Tl decay clarifies ${}^{205}$Pb dating in early Solar System
• Evidence for r-process delay in very metal-poor stars
• Inhomogeneous enrichment of radioactive nuclei in the Galaxy: Deposition of live Mn-53, Fe-60, Hf-182, and Pu-244 into deep-sea archives. Surfing the wave?
• Probing binary neutron star mergers in dense environments using afterglow counterparts
• Binary neutron star merger in common envelope jet supernovae
• The impact of turbulent mixing on the galactic r-process enrichment by binary neutron star mergers
• Proposed Lunar Measurements of $r$-Process Radioisotopes to Distinguish Origin of Deep-sea 244Pu
• R-process Rain from Binary Neutron Star Mergers in the Galactic Halo
• Enrichment of the Galactic disc with neutron-capture elements: Gd, Dy, and Th
• Did a Kilonova Set Off in Our Galactic Backyard 3.5 Myr ago?
• Stellar Migration and Chemical Enrichment in the Milky Way Disc: A Hybrid Model
• Where has all the $r$-process gone? Timescales for GRB-Kilonovae to Enrich their Host Galaxies
• Constraints on $R$-process Nucleosynthesis from ${}^{129}$I and ${}^{247}$Cm in the Early Solar System
• A path towards constraining the evolution of the interstellar medium and outflows in the Milky Way using APOGEE