{
  "id": "2003.01129",
  "version": "v1",
  "published": "2020-03-02T19:00:02.000Z",
  "updated": "2020-03-02T19:00:02.000Z",
  "title": "Turbulent mixing of r-process elements in the Milky Way",
  "authors": [
    "Paz Beniamini",
    "Kenta Hotokezaka"
  ],
  "comment": "10 pages, 10 figures",
  "categories": [
    "astro-ph.HE",
    "astro-ph.GA"
  ],
  "abstract": "We study turbulent gas diffusion affects on the observed $r$-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 metallicity values. 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 ratios. 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 $\\tau_{\\rm mix}\\approx 100-200\\mbox{ Myr}$. 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.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2020-03-02T19:00:02.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "milky way",
      "r-process elements",
      "early solar system",
      "process event",
      "process abundances"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 10,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}