Water Production of Interstellar Comet 3I/ATLAS from SOHO/SWAN Observations after Perihelion

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Auteurs principaux: Combi, M. R., Mâkinen, T., Bertaux, J. -L., Quemerais, E., Ferron, S., Lallement, R., Schmidt, W.
Format: Preprint
Publié: 2025
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author Combi, M. R.
Mâkinen, T.
Bertaux, J. -L.
Quemerais, E.
Ferron, S.
Lallement, R.
Schmidt, W.
author_facet Combi, M. R.
Mâkinen, T.
Bertaux, J. -L.
Quemerais, E.
Ferron, S.
Lallement, R.
Schmidt, W.
contents The Solar Wind ANisotropies (SWAN) all-sky hydrogen Lyman-alpha camera on the Solar and Heliosphere Observatory (SOHO) observed the hydrogen coma of interstellar comet 3I/ATLAS, also called C/2025 N1 (ATLAS), beginning on November 6, 2025, 9 days after perihelion. Water production rates were calculated from each image of 3I/ATLAS using the methodology of Makinen & Combi (2005, Icarus 177, 217) and fluorescence rates, g-factors, calculated using the daily solar Lyman-alpha fluxes from the LASP database (https://lasp.colorado.edu/lisird/data) corrected for solar rotation and for the comet heliocentric velocity. The method has been used for over 90 comet apparitions (Combi 2022; Combi et al. 2019). A water production rate of 3.17 x 10^29 s^-1 was found on November 6 when the comet was at a heliocentric distance of 1.40 au and at a sufficient solar elongation angle. It decreased over time after that, down to 1-2 x 10^28 s^-1 around 40 days post-perihelion (December 9).
format Preprint
id arxiv_https___arxiv_org_abs_2512_22354
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Water Production of Interstellar Comet 3I/ATLAS from SOHO/SWAN Observations after Perihelion
Combi, M. R.
Mâkinen, T.
Bertaux, J. -L.
Quemerais, E.
Ferron, S.
Lallement, R.
Schmidt, W.
Earth and Planetary Astrophysics
Astrophysics of Galaxies
The Solar Wind ANisotropies (SWAN) all-sky hydrogen Lyman-alpha camera on the Solar and Heliosphere Observatory (SOHO) observed the hydrogen coma of interstellar comet 3I/ATLAS, also called C/2025 N1 (ATLAS), beginning on November 6, 2025, 9 days after perihelion. Water production rates were calculated from each image of 3I/ATLAS using the methodology of Makinen & Combi (2005, Icarus 177, 217) and fluorescence rates, g-factors, calculated using the daily solar Lyman-alpha fluxes from the LASP database (https://lasp.colorado.edu/lisird/data) corrected for solar rotation and for the comet heliocentric velocity. The method has been used for over 90 comet apparitions (Combi 2022; Combi et al. 2019). A water production rate of 3.17 x 10^29 s^-1 was found on November 6 when the comet was at a heliocentric distance of 1.40 au and at a sufficient solar elongation angle. It decreased over time after that, down to 1-2 x 10^28 s^-1 around 40 days post-perihelion (December 9).
title Water Production of Interstellar Comet 3I/ATLAS from SOHO/SWAN Observations after Perihelion
topic Earth and Planetary Astrophysics
Astrophysics of Galaxies
url https://arxiv.org/abs/2512.22354