{
  "abstract": "We present new observations of a candidate O-type donor star in a high mass X-ray binary (HMXB) in M33. The candidate donor star is spatially coincident with a hard X-ray point source. The star's optical magnitude and colors are consistent with what is expected for a massive star. The four band optical/UV spectral energy distribution (SED) of the donor star is well fit by an O-giant model with an effective temperature of $\\sim$43 kK, mass of 75$_{+9}^{-0.3}$ $M_{\\odot}$, and surface gravity of log(g) of $\\sim$3.8. We present four epochs of optical spectroscopy of the donor star taken with the Keck/DEIMOS spectrograph over the course of approximately one year. Features in the star's spectrum are consistent with an O-type star. The star's spectrum exhibits a strong H$α$ emission line during all epochs of observation with a variable line profile. We measure the star's radial velocity for each epoch, which we use to fit for a systemic velocity. We find that the systemic velocity is offset from the local gas velocity from HI measurements, suggesting that the system has a peculiar velocity relative to the local gas. We observe a radial velocity shift in the He I absorption lines that is consistent with motion within a binary system.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2609.16174",
  "author_total": 11,
  "authors": [
    {
      "name": "Margaret Lazzarini"
    },
    {
      "name": "Lara Cullinane"
    },
    {
      "name": "Karoline Gilbert"
    },
    {
      "name": "Puragra GuhaThakurta"
    },
    {
      "name": "Kyros Hinton"
    },
    {
      "name": "Daniel Stern"
    },
    {
      "name": "O. Grace Telford"
    },
    {
      "name": "Tobin M. Wainer"
    },
    {
      "name": "Benjamin F. Williams"
    },
    {
      "name": "Robert Alexander"
    },
    {
      "name": "Ernesto Ramirez Jr"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/bt2bdbdeav0sr.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2609.16174",
  "fulltext_url": null,
  "id": "bt2bdbdeav0sr",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2609.16174",
  "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.HE"
    ],
    [
      "arxiv",
      "astro-ph.SR"
    ]
  ],
  "openalex": null,
  "pdf_url": "https://arxiv.org/pdf/2609.16174",
  "pmcid": null,
  "pmid": null,
  "published": "2026-09-14",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/bt2bdbdeav0sr.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:21:41Z",
      "native_id": "2609.16174",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2609.16174"
    }
  ],
  "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": "Optical Spectroscopy of a Candidate O-Star X-ray Binary in M33",
  "title_text": "Optical Spectroscopy of a Candidate O-Star X-ray Binary in M33",
  "type": "preprint",
  "updated_at": "2026-10-30T12:21:41Z",
  "url": "https://research.draconitic.com/paper/bt2bdbdeav0sr",
  "venue": "arXiv",
  "versions": [
    {
      "doi": "10.3847/1538-4357/ae9fef",
      "pid": "5psb9nw9m2fwm",
      "relation": "published-as",
      "title": "Optical Spectroscopy of a Candidate O-star X-Ray Binary in M33",
      "venue": "The Astrophysical Journal"
    }
  ]
}