{
  "abstract": "Gravitational-wave observations have revealed hundreds of stellar-mass black holes, yet only about two dozen are known in the Milky Way, almost all in binaries. We present POPKIN, a Python framework that couples single- and binary-star evolution with Galactic orbital dynamics to trace black-hole progenitors from the zero-age main sequence to the present-day isolated black-hole (IBH) population. Across ten models varying the supernova (SN) prescription, mass-transfer efficiency, and common-envelope ejection efficiency, the total IBH abundance is controlled primarily by the SN prescription. Our fiducial model, with a recently proposed metallicity- and stripping-history-dependent SN prescription, predicts $\\sim4\\times10^7$ IBHs in the Galaxy, including $\\sim8\\times10^4$ within $1\\,\\rm{kpc}$ of the Sun; alternative SN prescriptions predict $\\sim(1-2)\\times10^8$ IBHs. The fiducial model yields a bimodal mass distribution, peaking near $9\\,M_{\\odot}$ and $20\\,M_{\\odot}$, with a deficit at $13-17\\,M_{\\odot}$. This distinguishes it from alternative prescriptions, some of which populate the $2-5\\,M_{\\odot}$ mass-gap region. Non-kicked IBHs follow nearly circular orbits near the Galactic plane, with typical peculiar velocities of $20-30\\,\\rm{km\\,s^{-1}}$, whereas kicked systems undergo stronger radial migration and span a broader velocity range. We estimate $\\sim5\\times10^3$ accreting IBHs with $F_{\\rm X}>10^{-14}\\,\\rm{erg\\,s^{-1}\\,cm^{-2}}$, nearly all non-kicked; this estimate is sensitive to the adopted radiative-efficiency and hot-flow treatments. For a Roman-like bulge survey, our fiducial model predicts $\\sim360$ intrinsic IBH microlensing events over five years in a $1.70\\,\\rm{deg^2}$ effective area, before survey-selection effects. We propose that long-timescale microlensing events from IBHs can strongly constrain the SN physics governing stellar-mass black hole formation.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2609.29211",
  "author_total": 8,
  "authors": [
    {
      "name": "Jian-Guo He"
    },
    {
      "name": "Yong Shao"
    },
    {
      "name": "Yu-Dong Nie"
    },
    {
      "name": "Gui-Yu Wang"
    },
    {
      "name": "Xiao-Tian Xu"
    },
    {
      "name": "Chen Wang"
    },
    {
      "name": "Xiao-Jie Xu"
    },
    {
      "name": "Xiang-Dong Li"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/9qsr7p5h5edcw.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2609.29211",
  "fulltext_url": null,
  "id": "9qsr7p5h5edcw",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2609.29211",
  "language": null,
  "licence": "LicenseRef-arXiv-nonexclusive-1.0",
  "licence_label": "arXiv licence",
  "licence_source": "article",
  "licence_url": "http://arxiv.org/licenses/nonexclusive-distrib/1.0/",
  "metadata_licence": "CC0-1.0",
  "native_subjects": [
    [
      "arxiv",
      "astro-ph.GA"
    ],
    [
      "arxiv",
      "astro-ph.HE"
    ],
    [
      "arxiv",
      "astro-ph.SR"
    ],
    [
      "openalex",
      "3103|Astrophysical Phenomena and Observations"
    ]
  ],
  "openalex": "W7214333796",
  "pdf_url": "https://arxiv.org/pdf/2609.29211",
  "pmcid": null,
  "pmid": null,
  "published": "2026-09-24",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/9qsr7p5h5edcw.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:24:11Z",
      "native_id": "2609.29211",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2609.29211"
    }
  ],
  "subjects": [
    {
      "field": "astronomy",
      "origin": "arxiv:astro-ph.GA",
      "subfield": "galaxies"
    },
    {
      "field": "astronomy",
      "origin": "arxiv:astro-ph.HE",
      "subfield": "high-energy-astrophysics"
    },
    {
      "field": "astronomy",
      "origin": "arxiv:astro-ph.SR",
      "subfield": "stellar"
    }
  ],
  "title": "A Census of Stellar-mass Black Holes in the Milky Way with POPKIN. I. Isolated Black Holes",
  "title_text": "A Census of Stellar-mass Black Holes in the Milky Way with POPKIN. I. Isolated Black Holes",
  "type": "preprint",
  "updated_at": "2026-10-30T12:24:11Z",
  "url": "https://research.draconitic.com/paper/9qsr7p5h5edcw",
  "venue": "arXiv",
  "versions": []
}