Time-Domain Photometry and Activity Evolution of Interstellar Comet 3I/ATLAS with BHTOM
Abstract
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.
Cite
@article{arxiv.2603.01383,
title = {Time-Domain Photometry and Activity Evolution of Interstellar Comet 3I/ATLAS with BHTOM},
author = {A. Fraser Gillan and Łukasz Wyrzykowski and Przemysław J. Mikołajczyk and Krzysztof Kotysz and Erica Bufanda and Colin O. Chandler and Süleyman Fişek and Henry H. Hsieh and Michael S. P. Kelley and Priscila J. Pessi and James E. Robinson and Sinan Aliş and Wieńczysław Bykowski and Richard E. Cannon and Martin Dominik and Barbara Handzlik and Mehmet İçen and Sebastian Kurowski and Ahmet Cem Kutluay and Joysankar Majumdar and Çağlayan Nehir and David O'Neill and Sibel Ötken and Kangming Pu and Özlem Şimşir and Colin Snodgrass and Cihan Tuğrul Tezcan and Fatma Tezcan and Mauritz Wicker and Fuat Korhan Yelkenci and Michał Żejmo and Kendall Ackley and M. Andersen and C. Ávalos-Vega and Sergey Belkin and V. Bozza and Rene P. Breton and M. J. Burgdorf and Jorge Casares and Vik Dhillon and A. Donaldson and Martin J. Dyer and R. Figuera Jaimes and Duncan K. Galloway and T. C. Hinse and M. Hundertmark and E. Khalouei and Thomas Killestein and Rubina Kotak and Amit Kumar and Feng-Yuan Frey Liu and P. Longa-Peña and Joe Lyman and Luigi Mancini and A. Moharana and V. Molina and Kanthanakorn Noysena and Laura Kate Nuttall and Paul O'Brien and V. Okoth and C. Opitom and Don Pollacco and M. Rabus and Gavin Ramsay and S. Sajadian and A. Salinas San Martin and J. Skottfelt and J. Southworth and Danny Steeghs and J. Tregloan-Reed and Krzysztof Ulaczyk and R. Vieliute},
journal= {arXiv preprint arXiv:2603.01383},
year = {2026}
}
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