{
  "abstract": "We demonstrate that metallicity becomes identifiable for M-dwarf microlensing lenses out to bulge distances when multi-band lens photometry is combined with the angular Einstein radius, thereby defining the photometric--microlensing metallicity method. The cool atmospheres of M dwarfs contain abundant molecules, whose broad absorption bands make their positions in an optical--NIR color--absolute magnitude diagram sensitive to metallicity. The angular Einstein radius provides the mass--distance constraint needed to infer the lens absolute magnitude, while the intrinsic M-dwarf locus and reddening vector are non-parallel in color--color space, allowing the lens extinction and intrinsic color to be inferred simultaneously from its multi-band photometry, thereby recovering the lens intrinsic position in the metallicity-sensitive color--absolute magnitude diagram. The method requires three-band lens photometry spanning roughly the R, Z, and K bands, making it particularly well suited to Roman through its high-resolution F062, F087, and F213 imaging. With the planned Roman Galactic Bulge Time-Domain Survey (GBTDS) observations plus an additional $\\sim$8 hr of F062 imaging per field ($\\sim$40 hr in total) roughly a decade after Roman launch, host metallicities could be measured for $\\sim$150 planetary systems under the GBTDS yield forecast, with a typical $1σ$ precision of $\\sim$0.25 dex from our mock-recovery analysis. Applied homogeneously to GBTDS microlensing events with and without detected planets, the method would enable the first measurement of the occurrence--metallicity relation for cold low-mass planets beyond the snow line, constrain the low-metallicity cutoff for their formation, and extend occurrence--metallicity studies into the inner Galaxy.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2609.05265",
  "author_total": 5,
  "authors": [
    {
      "name": "Jiyuan Zhang"
    },
    {
      "name": "Gregory Green"
    },
    {
      "name": "Weicheng Zang"
    },
    {
      "name": "Hongjing Yang"
    },
    {
      "name": "Shude Mao"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/137q7gtcn4s8w.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2609.05265",
  "fulltext_url": null,
  "id": "137q7gtcn4s8w",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2609.05265",
  "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.EP"
    ],
    [
      "arxiv",
      "astro-ph.GA"
    ],
    [
      "arxiv",
      "astro-ph.IM"
    ],
    [
      "arxiv",
      "astro-ph.SR"
    ],
    [
      "openalex",
      "3103|Stellar, planetary, and galactic studies"
    ]
  ],
  "openalex": "W7211870140",
  "pdf_url": "https://arxiv.org/pdf/2609.05265",
  "pmcid": null,
  "pmid": null,
  "published": "2026-09-16",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/137q7gtcn4s8w.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:22:19Z",
      "native_id": "2609.05265",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2609.05265"
    }
  ],
  "subjects": [
    {
      "field": "astronomy",
      "origin": "arxiv:astro-ph.GA",
      "subfield": "galaxies"
    },
    {
      "field": "astronomy",
      "origin": "arxiv:astro-ph.IM",
      "subfield": "instrumentation-methods"
    },
    {
      "field": "astronomy",
      "origin": "arxiv:astro-ph.EP",
      "subfield": "planetary"
    },
    {
      "field": "astronomy",
      "origin": "arxiv:astro-ph.SR",
      "subfield": "stellar"
    }
  ],
  "title": "Enabling Metallicity Measurements of M-dwarf Microlensing Lenses out to the Galactic Bulge",
  "title_text": "Enabling Metallicity Measurements of M-dwarf Microlensing Lenses out to the Galactic Bulge",
  "type": "preprint",
  "updated_at": "2026-10-30T12:22:19Z",
  "url": "https://research.draconitic.com/paper/137q7gtcn4s8w",
  "venue": "arXiv",
  "versions": []
}