Comprehensive Visible and Near-infrared Keck and Gemini Monitoring and Characterization of Interstellar Comet 3I/ATLAS during its Encounter with the Solar System

@misc{bolin2026comprehensive,
  title = {{Comprehensive Visible and Near-infrared Keck and Gemini Monitoring and Characterization of Interstellar Comet 3I/ATLAS during its Encounter with the Solar System}},
  author = {Bryce T. Bolin and Jeffrey Cooke and Brian C. Lemaux and Marco Micheli and Davide Farnocchia and Laura-May Abron and Leo Y. Alcorn and Michael W. Coughlin and Christoffer Fremling and Josef Hanuš and Willem B. Hoogendam and Carl Ingebretsen and Oleksandra Ivanova and David O. Jones and Piera King and Ludmilla Kolokolova and Keith S. Noll and Filipp D. Romanov and Benjamin J. Shappee and Karleyne Silva and Matt Wahl and Pablo Candia and Kristin Chiboucas and Eleazar R. Carrasco and Veronica Firpo and Jeong-Eun Heo and Jameeka Marshall and Emily Peavy and Erin Figura and Denise Hung and Ariel Graykowski and Teo Močnik and Matias Rodriguez and David J. Tholen and Peter Vereš and Leila Alamos and Eunchong Kim and Jen Miller and Percy Gomez and Heather Hershley and Michael Lundquist and Rita Morris and Hyewon Suh and Emanuele Paolo Farina and Ryan Ridden and Mark Suhr},
  howpublished = {arXiv},
  year = {2026},
  month = oct,
  doi = {10.48550/arxiv.2610.32972},
  eprint = {2610.32972},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2610.32972},
  note = {CC0},
}

TY  - UNPB
TI  - Comprehensive Visible and Near-infrared Keck and Gemini Monitoring and Characterization of Interstellar Comet 3I/ATLAS during its Encounter with the Solar System
AU  - Bryce T. Bolin
AU  - Jeffrey Cooke
AU  - Brian C. Lemaux
AU  - Marco Micheli
AU  - Davide Farnocchia
AU  - Laura-May Abron
AU  - Leo Y. Alcorn
AU  - Michael W. Coughlin
AU  - Christoffer Fremling
AU  - Josef Hanuš
AU  - Willem B. Hoogendam
AU  - Carl Ingebretsen
AU  - Oleksandra Ivanova
AU  - David O. Jones
AU  - Piera King
AU  - Ludmilla Kolokolova
AU  - Keith S. Noll
AU  - Filipp D. Romanov
AU  - Benjamin J. Shappee
AU  - Karleyne Silva
AU  - Matt Wahl
AU  - Pablo Candia
AU  - Kristin Chiboucas
AU  - Eleazar R. Carrasco
AU  - Veronica Firpo
AU  - Jeong-Eun Heo
AU  - Jameeka Marshall
AU  - Emily Peavy
AU  - Erin Figura
AU  - Denise Hung
AU  - Ariel Graykowski
AU  - Teo Močnik
AU  - Matias Rodriguez
AU  - David J. Tholen
AU  - Peter Vereš
AU  - Leila Alamos
AU  - Eunchong Kim
AU  - Jen Miller
AU  - Percy Gomez
AU  - Heather Hershley
AU  - Michael Lundquist
AU  - Rita Morris
AU  - Hyewon Suh
AU  - Emanuele Paolo Farina
AU  - Ryan Ridden
AU  - Mark Suhr
PY  - 2026
DA  - 2026/10/23
PB  - arXiv
DO  - 10.48550/arxiv.2610.32972
UR  - https://arxiv.org/abs/2610.32972
AB  - 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±0.029, r−i=0.237±0.025, and i−z=0.109±0.022 mag show no significant change across perihelion. Phase-corrected red-band activity follows Afρ∝ r_h^−2.10±0.14 inbound and r_h^−3.34±0.43 outbound. Transverse-width and sunward-plume speeds imply dust losses of 2.7×10^9 and 1.0×10^10 kg over 2025 July 3--2026 May 15 for 1-μm--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±0.014 on 2025 September 14--15 to 0.481±0.080 on 2025 November 26, while C_3/CN fell from 0.327±0.024 on 2025 August 28 to 0.214±0.009 on 2025 September 14--15. MOSFIRE NIR imaging on 2025 July 11 gives Y−J=0.466±0.143, J−H=0.239±0.052, H−K_s=0.454±0.150, and J−K_s=0.693±0.202 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±0.051 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.
ER  -