{
  "abstract": "We present 14 optical imaging and eight optical spectroscopic epochs of interstellar comet 3I/ATLAS from Keck/LRIS and Gemini/GMOS, two near-infrared (NIR) imaging epochs from Keck/MOSFIRE, and four NIR spectroscopic epochs from Gemini/Flamingos-2 and GNIRS, obtained between 2025 July and 2026 May. Mean GMOS colors of $g-r=0.732\\pm0.029$, $r-i=0.237\\pm0.025$, and $i-z=0.109\\pm0.022$ mag show no significant change across perihelion. Phase-corrected red-band activity follows $Afρ\\propto r_h^{-2.10\\pm0.14}$ inbound and $r_h^{-3.34\\pm0.43}$ outbound. Transverse-width and sunward-plume speeds imply dust losses of $2.7\\times10^9$ and $1.0\\times10^{10}$ kg over 2025 July 3--2026 May 15 for 1-$μ$m--1-mm grains, equivalent to global layers of 0.26 and 0.99 m under the adopted grain and nucleus assumptions. The concentrated coma, compact sunward feature, and antisolar tail seen on 2025 August 27 broadened by 2025 November 26; extended dust persisted through 2026 February 17. C$_2$/CN nearly doubled from $0.257\\pm0.014$ on 2025 September 14--15 to $0.481\\pm0.080$ on 2025 November 26, while C$_3$/CN fell from $0.327\\pm0.024$ on 2025 August 28 to $0.214\\pm0.009$ on 2025 September 14--15. MOSFIRE NIR imaging on 2025 July 11 gives $Y-J=0.466\\pm0.143$, $J-H=0.239\\pm0.052$, $H-K_s=0.454\\pm0.150$, and $J-K_s=0.693\\pm0.202$ mag. Spectra give $J-H=0.24$ mag on 2025 September 5--6 and $J-H=0.27$--0.28 and $J-K_s=0.21$--0.22 mag on 2025 December 1--2 over the retained passband intervals. Model-calibrated imaging on 2026 February 6 gives near-solar $J-K_s=0.303\\pm0.051$ mag. No water-ice absorption is robust to the tested continuum and calibration choices in the NIR spectra. These observations provide a lasting record of the comet's evolution through the Solar System and a benchmark for studying and monitoring future interstellar objects.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2610.32972",
  "author_total": 46,
  "authors": [
    {
      "name": "Bryce T. Bolin"
    },
    {
      "name": "Jeffrey Cooke"
    },
    {
      "name": "Brian C. Lemaux"
    },
    {
      "name": "Marco Micheli"
    },
    {
      "name": "Davide Farnocchia"
    },
    {
      "name": "Laura-May Abron"
    },
    {
      "name": "Leo Y. Alcorn"
    },
    {
      "name": "Michael W. Coughlin"
    },
    {
      "name": "Christoffer Fremling"
    },
    {
      "name": "Josef Hanuš"
    },
    {
      "name": "Willem B. Hoogendam"
    },
    {
      "name": "Carl Ingebretsen"
    },
    {
      "name": "Oleksandra Ivanova"
    },
    {
      "name": "David O. Jones"
    },
    {
      "name": "Piera King"
    },
    {
      "name": "Ludmilla Kolokolova"
    },
    {
      "name": "Keith S. Noll"
    },
    {
      "name": "Filipp D. Romanov"
    },
    {
      "name": "Benjamin J. Shappee"
    },
    {
      "name": "Karleyne Silva"
    },
    {
      "name": "Matt Wahl"
    },
    {
      "name": "Pablo Candia"
    },
    {
      "name": "Kristin Chiboucas"
    },
    {
      "name": "Eleazar R. Carrasco"
    },
    {
      "name": "Veronica Firpo"
    },
    {
      "name": "Jeong-Eun Heo"
    },
    {
      "name": "Jameeka Marshall"
    },
    {
      "name": "Emily Peavy"
    },
    {
      "name": "Erin Figura"
    },
    {
      "name": "Denise Hung"
    },
    {
      "name": "Ariel Graykowski"
    },
    {
      "name": "Teo Močnik"
    },
    {
      "name": "Matias Rodriguez"
    },
    {
      "name": "David J. Tholen"
    },
    {
      "name": "Peter Vereš"
    },
    {
      "name": "Leila Alamos"
    },
    {
      "name": "Eunchong Kim"
    },
    {
      "name": "Jen Miller"
    },
    {
      "name": "Percy Gomez"
    },
    {
      "name": "Heather Hershley"
    },
    {
      "name": "Michael Lundquist"
    },
    {
      "name": "Rita Morris"
    },
    {
      "name": "Hyewon Suh"
    },
    {
      "name": "Emanuele Paolo Farina"
    },
    {
      "name": "Ryan Ridden"
    },
    {
      "name": "Mark Suhr"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/8a6924j3xv1j1.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2610.32972",
  "fulltext_url": null,
  "id": "8a6924j3xv1j1",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2610.32972",
  "language": null,
  "licence": "CC0-1.0",
  "licence_label": "CC0",
  "licence_source": "article",
  "licence_url": "http://creativecommons.org/publicdomain/zero/1.0/",
  "metadata_licence": "CC0-1.0",
  "native_subjects": [
    [
      "arxiv",
      "astro-ph.EP"
    ],
    [
      "arxiv",
      "astro-ph.GA"
    ],
    [
      "openalex",
      "3103|Astro and Planetary Science"
    ]
  ],
  "openalex": "W7223678924",
  "pdf_url": "https://arxiv.org/pdf/2610.32972",
  "pmcid": null,
  "pmid": null,
  "published": "2026-10-23",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/8a6924j3xv1j1.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:35:15Z",
      "native_id": "2610.32972",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2610.32972"
    }
  ],
  "subjects": [
    {
      "field": "astronomy",
      "origin": "arxiv:astro-ph.GA",
      "subfield": "galaxies"
    },
    {
      "field": "astronomy",
      "origin": "arxiv:astro-ph.EP",
      "subfield": "planetary"
    }
  ],
  "title": "Comprehensive Visible and Near-infrared Keck and Gemini Monitoring and Characterization of Interstellar Comet 3I/ATLAS during its Encounter with the Solar System",
  "title_text": "Comprehensive Visible and Near-infrared Keck and Gemini Monitoring and Characterization of Interstellar Comet 3I/ATLAS during its Encounter with the Solar System",
  "type": "preprint",
  "updated_at": "2026-10-30T12:35:15Z",
  "url": "https://research.draconitic.com/paper/8a6924j3xv1j1",
  "venue": "arXiv",
  "versions": []
}