{
  "abstract": "The majority of very close binaries (orbital periods P < 5 days) are in triples. Previous studies surmised that the tertiary hardened the inner binary via Kozai-Lidov cycles coupled with tidal friction. Alternatively, the trend could be due to a common origin, e.g., more massive molecular cores and protostellar disks are more likely to fragment twice into a triple and harden the inner binary to very short periods via disk migration. Disk migration occurs during the embedded Class I protostellar phase while secular evolution with a tertiary occurs on much longer timescales. To determine the dominant migration mechanism, I accurately measure the very close binary fractions of both late-type and early-type primaries in star-forming environments. After combining five surveys, the late-type Class II/III T Tauri very close binary fraction is F_VCB = 2.1_{-0.5}^{+1.0}%, which is consistent with the measurement for late-type field main-sequence stars (1.7% +/- 0.1%). More than 85% of very close late-type binaries hardened via disk migration during the Class I protostellar phase. I next measure the OGLE-III eclipsing binary (EB) fractions of young massive stars in the LMC. The very close EB fractions of massive young stellar objects (YSOs; F_VCEB = 8.3_{-3.2}^{+4.9}%), OB stars near massive YSOs (4.7% +/- 0.8%), and OB stars in small, young H II regions (6.4% +/- 1.5%) are consistent with each other and the measurement for OB stars in slightly older clusters (4.7% +/- 0.3%). More than 90% of very close massive binaries hardened via disk migration during the embedded protostellar phase.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2609.00426",
  "author_total": 1,
  "authors": [
    {
      "name": "Maxwell Moe"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/66n44zav21pws.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2609.00426",
  "fulltext_url": null,
  "id": "66n44zav21pws",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2609.00426",
  "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.SR"
    ]
  ],
  "openalex": null,
  "pdf_url": "https://arxiv.org/pdf/2609.00426",
  "pmcid": null,
  "pmid": null,
  "published": "2026-09-01",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/66n44zav21pws.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:18:00Z",
      "native_id": "2609.00426",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2609.00426"
    }
  ],
  "subjects": [
    {
      "field": "astronomy",
      "origin": "arxiv:astro-ph.SR",
      "subfield": "stellar"
    }
  ],
  "title": "The Formation of Very Close Binary Stars",
  "title_text": "The Formation of Very Close Binary Stars",
  "type": "preprint",
  "updated_at": "2026-10-30T12:18:00Z",
  "url": "https://research.draconitic.com/paper/66n44zav21pws",
  "venue": "arXiv",
  "versions": []
}