Central Bureau for Astronomical Telegrams
IAUC 6362: C/1996 B2
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Circular No. 6362
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Postal Address: Central Bureau for Astronomical Telegrams
Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
IAUSUBS@CFA.HARVARD.EDU or FAX 617-495-7231 (subscriptions)
BMARSDEN@CFA.HARVARD.EDU or DGREEN@CFA.HARVARD.EDU (science)
Phone 617-495-7244/7440/7444 (for emergency use only)
COMET C/1996 B2 (HYAKUTAKE)
D. Lis, J. Keene, K. Young, and T. Phillips, California
Institute of Technology Submillimeter Observatory; E. Bergin,
Smithsonian Astrophysical Observatory; P. Goldsmith, Cornell
University; D. Bockelee-Morvan, J. Crovisier, and D. Gautier,
Observatoire de Paris-Meudon; A. Wootten, National Radio Astronomy
Observatory; D. Despois, Observatoire de Bordeaux; and T. Owen,
University of Hawaii, report the detection of the 110-000
rotational line of HDO at 464.9 GHz in comet C/1996 B2, using the
Caltech Submillimeter Observatory on Mar. 23.5 and 24.5 UT. The
integrated line intensity on the antenna temperature scale is 0.34
+/- 0.05 K km/s. Assuming local thermal equilibrium at 80 K, we
derive Q(HDO)= 1.0 x 10E26 mol/s. This corresponds to a
[HDO]/[H2O] ratio of 2.8 x 10E-4, using the water-production rate
measured from OH observations with IUE (IAUC 6355). These
preliminary results suggest a [D]/[H] ratio of 1.4 x 10E-4, which
is by a factor of two lower than that measured by mass
spectroscopy in water in comet 1P/Halley (Balsiger et al. 1995, J.
Geophys. Res. 100, 5827; Eberhardt et al. 1995, A.Ap. 302, 301)
and very close to the standard mean ocean water value of 1.6 x
10E-4."
A. Wootten and B. Butler, National Radio Astronomy Observatory
(NRAO); D. Bockelee-Morvan and J. Crovisier, Observatoire de Paris-
Meudon; P. Palmer, University of Chicago; D. Despois, Observatoire
de Bordeaux; and D. Yeomans, Jet Propulsion Laboratory, report the
detection of the (J,K) = (1,1) and (3,3) inversion-rotation lines
of ammonia at 1.3 cm on Mar. 24.5 UT, using the NRAO 43-m telescope
at Green Bank: "We measure an integrated intensity in the (3,3)
line of 0.22 +/- 0.013 and 0.13 +/- 0.015 K km sE-1 in the main
component and inner hyperfine components of the (1,1) line. From
these four lines, we derive the rotational temperature of the
ammonia molecules to be 60 K, assuming an abundance ratio of ortho-
to para-ammonia of 3. Ammonia appears to be produced at a rate
Q(NH3) = 1 x 10E27 mol/s, or only 0.25 percent that of water
molecules, as reported on IAUC 6355 and derived from IUE
observations of OH. Such an abundance lies at the extreme lower
range of values deduced from 1P/Halley observations of NH and NH2
radicals, and much below those measured for 1P/Halley from Giotto
mass spectroscopy."
(C) Copyright 1996 CBAT
1996 March 28 (6362) Daniel W. E. Green
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