{
  "abstract": "The iconic Teapot asterism in Sagittarius is particularly rich in intermediate-mass stars in multiple systems. Here we combine VLTI/GRAVITY, archival spectroscopic observations, past radial velocity measurements and photometry to solve for the orbital and stellar parameters of the binary Nandou=Phi Sagittarii. It has a period $P=238.844\\pm0.011$ days, a semi-major axis $a=1.32\\pm0.10\\text{ au}$ and eccentricity $e=0.418\\pm0.004$. The precision in the dynamical masses $M_A=3.8\\pm0.9 M_{\\odot}$ and $M_B=1.6\\pm0.4 M_{\\odot}$ is currently limited by the parallax $p=12.5\\pm1.0 \\text{ mas}$. We find that the original Hipparcos 1997 Intermediate Astrometric Data (IAD) are consistent with the expected photocenter semi-major axis $a_{\\mathrm{phot}} \\sim 5 \\text{ mas}$, while the IAD from the Hipparcos 2007 new reduction yield a too small $a_{\\mathrm{phot}} = 1.7\\pm0.3 \\text{ mas}$, confirming the suspicion that a too aggressive modeling of the satellite attitude can lead to overfitting that suppresses the orbital motion. Matching the primary's temperature $T_{\\mathrm{eff,A}} = 12000\\pm250 \\text{ K}$ and radius $R_{\\mathrm{A}} = 5.1\\pm 0.4 R_{\\odot}$ to stellar evolutionary models implies that it is a $M_A \\simeq 4 M_{\\odot}$ star near the end of the main-sequence. Nandou will eventually most likely become a symbiotic star.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2611.05455",
  "author_total": 2,
  "authors": [
    {
      "name": "Idel Waisberg"
    },
    {
      "name": "Boaz Katz"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/aj2qz6n587eh6.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2611.05455",
  "fulltext_url": null,
  "id": "aj2qz6n587eh6",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2611.05455",
  "language": null,
  "licence": "CC-BY-4.0",
  "licence_label": "CC BY 4.0",
  "licence_source": "article",
  "licence_url": "http://creativecommons.org/licenses/by/4.0/",
  "metadata_licence": "CC0-1.0",
  "native_subjects": [
    [
      "arxiv",
      "astro-ph.GA"
    ],
    [
      "arxiv",
      "astro-ph.SR"
    ]
  ],
  "openalex": null,
  "pdf_url": "https://arxiv.org/pdf/2611.05455",
  "pmcid": null,
  "pmid": null,
  "published": "2026-11-03",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/aj2qz6n587eh6.ris",
  "sources": [
    {
      "first_seen": "2026-11-05T15:20:56Z",
      "native_id": "2611.05455",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2611.05455"
    }
  ],
  "subjects": [
    {
      "field": "astronomy",
      "origin": "arxiv:astro-ph.GA",
      "subfield": "galaxies"
    },
    {
      "field": "astronomy",
      "origin": "arxiv:astro-ph.SR",
      "subfield": "stellar"
    }
  ],
  "title": "Brewing another binary in the Teapot: Nandou=Phi Sagittarii",
  "title_text": "Brewing another binary in the Teapot: Nandou=Phi Sagittarii",
  "type": "preprint",
  "updated_at": "2026-11-09T00:20:18Z",
  "url": "https://research.draconitic.com/paper/aj2qz6n587eh6",
  "venue": "arXiv",
  "versions": []
}