[Iaude] CBET 4551: 20180829 : COMET 21P/GIACOBINI-ZINNER

quai at eps.harvard.edu quai at eps.harvard.edu
Wed Aug 29 09:57:17 EDT 2018

                                                  Electronic Telegram No. 4551
Central Bureau for Astronomical Telegrams
Mailing address:  Hoffman Lab 209; Harvard University;
 20 Oxford St.; Cambridge, MA  02138; U.S.A.
e-mail:  cbatiau at eps.harvard.edu (alternate cbat at iau.org)
URL http://www.cbat.eps.harvard.edu/index.html
Prepared using the Tamkin Foundation Computer Network

     N. Roth, E. Gibb, and M. Saki, University of Missouri at St. Louis; M.
DiSanti, Goddard Space Flight Center, NASA; N. Dello Russo and R. Vervack,
Applied Physics Laboratory, Johns Hopkins University; B. Bonev, American
University; A. McKay, Universities Space Research Association and Goddard
Space Flight Center; and H. Kawakita, Kyoto Sangyo University, report
preliminary water-production rates, and also production-rate ratios relative
to H_2O, for nine trace volatiles in the Jupiter-family comet 21P, from
observations using the NASA Infrared Telescope Facility Spectrograph,
iSHELL, during July 25-31 UT (r = 1.20-1.16 AU, Delta = 0.64-0.59 AU).
Over the course of the observations, the measured water-production rate was
approximately 3.6 x 10E28 molecules/s and was consistent with a rotational
temperature of 50 K.  Measured abundance ratios (preliminary results)
relative to H_2O (in percent) are as follows:  CO, 1.8; OCS, < 0.1 (3-sigma
upper limit); H_2CO, < 0.15 (3-sigma); C_2H_6, 0.28; CH_3OH, 1.3; CH_4,
0.38; HCN, 0.23; C_2H_2, < 0.15 (3-sigma); NH_3, < 0.74 (3-sigma).  The
secure detections of CO and especially CH_4 are particularly important, as
these two molecules have long been significantly understudied in Jupiter-
family comets.  CO was measured simultaneously with H_2O on four dates,
thereby permitting a search for potential day-to-day changes in its

NOTE: These 'Central Bureau Electronic Telegrams' are sometimes
      superseded by text appearing later in the printed IAU Circulars.

                         (C) Copyright 2018 CBAT
2018 August 29                   (CBET 4551)              Daniel W. E. Green

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