{
  "abstract": "We present the results of high-resolution emission spectroscopy of the hot Jupiter KELT-2A~b using IGRINS-2 on the Gemini-North telescope, covering the $H$- and $K$-bands at a spectral resolution of $R \\sim 45{,}000$. Observations were carried out over five nights, covering both pre- and post-eclipse orbital phases. Stellar and telluric contaminations are removed via singular value decomposition. We detect $\\rm H_2O$ at a signal-to-noise ratio of {6.57}, confirming the previous result at a higher significance. While $\\rm ^{12}CO$ is identified in the log-likelihood map near the expected planetary velocity, a definitive detection of $\\rm ^{12}CO$ remains elusive given the current data quality. We perform atmospheric retrieval both with IGRINS-2 data alone and jointly with archival \\textit{Spitzer}/IRAC photometric data points. The retrieved temperature--pressure profile is non-inverted, consistent with prior observations. {From the joint fit we constrain the water abundance to} $\\rm log(H_2O) = {-3.78^{+0.27}_{-0.20}}$ {with the free chemistry model}. {The chemical equilibrium model yields} $\\rm C/O={ 0.19^{+0.12}_{-0.07}}$, $\\rm [C/H]=-0.81^{+0.41}_{-0.34}$, and $\\rm [O/H] = -0.37^{+0.27}_{-0.17}${: the C/O ratio agrees with the stellar value, while the carbon and oxygen abundances are moderately depleted relative to the host star, though still consistent at the $\\sim2σ$ level.} If confirmed, {this combination of a stellar C/O ratio with a sub-stellar metallicity is difficult to reconcile with gas accretion between the $\\rm{H_2O}$ and CO snowlines, which predicts a super-stellar C/O. It instead points to the accretion of metal-depleted gas outside the CO snowline with only limited planetesimal enrichment, and hence to a disk-free, high-eccentricity migration history.}",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2610.19377",
  "author_total": 16,
  "authors": [
    {
      "name": "Yuya Hayashi"
    },
    {
      "name": "Stevanus K. Nugroho"
    },
    {
      "name": "Shota Notsu"
    },
    {
      "name": "Changeat Quentin"
    },
    {
      "name": "Peter C. B. Smith"
    },
    {
      "name": "Krishna Kanumalla"
    },
    {
      "name": "Michael R. Line"
    },
    {
      "name": "Jorge A. Sanchez"
    },
    {
      "name": "Tomohiro C. Yoshida"
    },
    {
      "name": "Kazumasa Ohno"
    },
    {
      "name": "Hideko Nomura"
    },
    {
      "name": "Taiki Kagetani"
    },
    {
      "name": "Norio Narita"
    },
    {
      "name": "Kiyoe Kawauchi"
    },
    {
      "name": "Akihiko Fukui"
    },
    {
      "name": "Enric Palle"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/5hrmhr72ceyhb.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2610.19377",
  "fulltext_url": null,
  "id": "5hrmhr72ceyhb",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2610.19377",
  "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"
    ],
    [
      "openalex",
      "3103|Stellar, planetary, and galactic studies"
    ]
  ],
  "openalex": "W7222244068",
  "pdf_url": "https://arxiv.org/pdf/2610.19377",
  "pmcid": null,
  "pmid": null,
  "published": "2026-10-21",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/5hrmhr72ceyhb.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:34:18Z",
      "native_id": "2610.19377",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2610.19377"
    }
  ],
  "subjects": [
    {
      "field": "astronomy",
      "origin": "arxiv:astro-ph.EP",
      "subfield": "planetary"
    }
  ],
  "title": "Emission spectroscopy of KELT-2A b with Gemini-North/IGRINS-2: hints of a stellar C/O ratio and sub-stellar metallicity",
  "title_text": "Emission spectroscopy of KELT-2A b with Gemini-North/IGRINS-2: hints of a stellar C/O ratio and sub-stellar metallicity",
  "type": "preprint",
  "updated_at": "2026-10-30T12:34:18Z",
  "url": "https://research.draconitic.com/paper/5hrmhr72ceyhb",
  "venue": "arXiv",
  "versions": []
}