Electronic Telegram No. 5628
Central Bureau for Astronomical Telegrams
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COMET 3I/ATLAS
     Y.-J. Kuan, National Taiwan Normal University (NTNU); Y.-L. Chuang,
Academia Sinica Institute of Astronomy and Astrophysics (ASIAA); I. M.
Coulson, East Asian Observatory; M. A. Cordiner, Goddard Space Flight Center
(GSFC), NASA, and Catholic University; S. B. Charnley and S. N. Milam, GSFC;
N. X. Roth, GSFC and American University; M.-K. Lin, ASIAA; Y.-N. Lee, NTNU;
and B. Pimpanuwat, National Astronomical Research Institute of Thailand,
report the detection of multiple emission lines of CH_3OH at about 241.8 GHz
from comet 3I/ATLAS at heliocentric distance r = 1.39 AU.  Observations were
made on Oct. 20 UT with the James Clerk Maxwell Telescope on Mauna Kea, using
the 'U'u (A-band) heterodyne receiver and the ACSIS spectroscopic backend.
Analysis using the SUBLIME code (Cordiner et al. 2022, Ap.J. 929, 38), and
adopting Q(H_2O) = 6 x 10**28 molecules/s (Crovisier et al., CBET 5625) yields
an expansion velocity in the coma of 0.41 (+/- 0.14) km/s (similar to their
measure from HCN:3-2 spectra, as reported on CBET 5608); a production rate of
CH_3OH molecules, Q(CH_3OH), of 4.2 (+/- 0.6) x 10**27 molecules/s; and a
kinetic temperature for the gas, T_kin, of 66 (+/- 12) K.  The authors derive,
then, a relative abundance of methanol-to-water of 0.070 (+/- 0.011).


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                         (C) Copyright 2025 CBAT
2025 October 30                  (CBET 5628)              Daniel W. E. Green