{
  "abstract": "A thin, arc-shaped shell is discovered surrounding VX Sagittarii (VX Sgr), the largest known CSM shell around an RSG at a scale $r\\sim0.59\\,\\mathrm{pc}$. The nebula has an extinction-corrected H$α$ intensity $I_{\\mathrm{H}α}\\sim38\\,\\mathrm{R}$ and an ionized mass $\\sim0.1\\,\\mathrm{M_\\odot}$. The slow $12\\,\\mathrm{km\\,s}^{-1}$ peculiar velocity of VX Sgr and the lack of far-infrared emission in the arc indicate that it is not produced by a bow shock, but is likely instead steady RSG wind or ejecta that is photoionized by a nearby $\\mathrm{O}$- or $\\mathrm{B}$- type star. The nature of VX Sgr is debated in the literature as a red supergiant/hypergiant (RSG/RHG), super-AGB star, or Thorne--Żytkow Object (TŻO). Using the kinematic age of the Sgr OB1 association, the super-AGB model is disfavored. A spectroscopic test of the arc is proposed to potentially distinguish an RSG from a possible TŻO. The mass-loss rate is estimated from the geometry and emission measure of the shell, finding $\\dot{M}\\approx4\\times10^{-5}\\,\\mathrm{M}_\\odot\\,\\mathrm{yr}^{-1}$. The future interaction of the supernova (SN) ejecta of VX Sgr and the surrounding circumstellar material (CSM) is briefly explored through the mass ratio $Λ$ of the shell and SN ejecta; the interaction would likely not have a significant effect on the SN forward shock.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2610.20689",
  "author_total": 1,
  "authors": [
    {
      "name": "Julian Shapiro"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/b4735zcjfvys5.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2610.20689",
  "fulltext_url": null,
  "id": "b4735zcjfvys5",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2610.20689",
  "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",
      "3103|Stellar, planetary, and galactic studies"
    ]
  ],
  "openalex": "W7222543094",
  "pdf_url": "https://arxiv.org/pdf/2610.20689",
  "pmcid": null,
  "pmid": null,
  "published": "2026-10-14",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/b4735zcjfvys5.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:29:50Z",
      "native_id": "2610.20689",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2610.20689"
    }
  ],
  "subjects": [
    {
      "field": "astronomy",
      "origin": "arxiv:astro-ph.GA",
      "subfield": "galaxies"
    },
    {
      "field": "astronomy",
      "origin": "arxiv:astro-ph.SR",
      "subfield": "stellar"
    }
  ],
  "title": "A Parsec-scale Circumstellar Shell Around VX Sgr: Mass Loss and RSG/TŻO Nature",
  "title_text": "A Parsec-scale Circumstellar Shell Around VX Sgr: Mass Loss and RSG/TŻO Nature",
  "type": "preprint",
  "updated_at": "2026-10-30T12:29:50Z",
  "url": "https://research.draconitic.com/paper/b4735zcjfvys5",
  "venue": "arXiv",
  "versions": []
}