Time-Domain Photometry and Activity Evolution of Interstellar Comet 3I/ATLAS with BHTOM
Time-domain photometric monitoring is essential for characterizing cometary evolution, particularly for rare interstellar objects with limited observing opportunities.
We aimed to characterize the pre-perihelion photometric behavior and dust activity of the interstellar comet 3I/ATLAS, and to test the capability of the Black Hole Target and Observation Manager (BHTOM) platform and telescope network for coordinated high-cadence non-sidereal observations.
We obtained 70 days of time-series photometry of 3I/ATLAS from 2025 July 4 – September 11 using 16 telescopes and 1554 images. The data were processed and calibrated with the BHTOM pipeline. High-cadence, multi-band imaging was used to measure the rotation period and color evolution, while the dust activity was quantified via Afp measurements. We present a pre-perihelion light curve of 3I/ATLAS from Rh = 3.18 – 2.19 au, which exhibited a steady increase of ~3 magnitudes with no evidence of anomalous behavior.
We measured a rotation period of P_rot = 15.98 +/- 0.08 h. The relative dust production increased from A(0)fp ~600 – 1100 cm, and the upper limit on the dust mass-loss rate increased from \leq 217 kg/s to \leq 328 kg/s.
We measured an activity index of n = -1.24 +/- 0.02, consistent with a well-developed dust coma. The colors were statistically non-changing, with only a weak, non-significant tendency for 3I/ATLAS to become bluer at 3.5 > Rh > 2.2 au.
A. Fraser Gillan, Łukasz Wyrzykowski, Przemysław J. Mikołajczyk, Krzysztof Kotysz, Erica Bufanda, Colin O. Chandler, Süleyman Fişek, Henry H. Hsieh, Michael S. P. Kelley, Priscila J. Pessi, James E. Robinson, Sinan Aliş, Wieńczysław Bykowski, Richard E. Cannon, Martin Dominik, Barbara Handzlik, Mehmet İçen, Sebastian Kurowski, Ahmet Cem Kutluay, Joysankar Majumdar, Çağlayan Nehir, David O’Neill, Sibel Ötken, Kangming Pu, Özlem Şimşir, Colin Snodgrass, Cihan Tuğrul Tezcan, Fatma Tezcan, Mauritz Wicker, Fuat Korhan Yelkenci, Michał Żejmo, Kendall Ackley, M. Andersen, C. Ávalos-Vega, Sergey Belkin, V. Bozza, Rene P. Breton, M. J. Burgdorf, Jorge Casares, Vik Dhillon, A. Donaldson, Martin J. Dyer, R. Figuera Jaimes, Duncan K. Galloway, T. C. Hinse, M. Hundertmark, E. Khalouei, Thomas Killestein, Rubina Kotak, Amit Kumar, Feng-Yuan Frey Liu, P. Longa-Peña, Joe Lyman, Luigi Mancini, A. Moharana, V. Molina, Kanthanakorn Noysena, Laura Kate Nuttall, Paul O’Brien, V. Okoth, C. Opitom, Don Pollacco, M. Rabus, Gavin Ramsay, S. Sajadian, A. Salinas San Martin, J. Skottfelt, J. Southworth, Danny Steeghs, J. Tregloan-Reed, Krzysztof Ulaczyk, R. Vieliute
Comments: Comments welcome! To be submitted to Astronomy & Astrophysics
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Astrophysics of Galaxies (astro-ph.GA); Instrumentation and Methods for Astrophysics (astro-ph.IM)
Cite as: arXiv:2603.01383 [astro-ph.EP](or arXiv:2603.01383v1 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2603.01383
Focus to learn more
Submission history
From: Fraser Gillan
[v1] Mon, 2 Mar 2026 02:26:08 UTC (17,117 KB)
https://arxiv.org/abs/2603.01383
Astrobiology,
