Central Bureau for Astronomical Telegrams
IAUC 6353: C/1996 B2
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Circular No. 6353
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)
H. E. Matthews, Herzberg Institute of Astrophysics, Ottawa,
and Joint Astronomy Centre (JAC), Hilo; N. Biver, Meudon Observatory
(MO); M. Senay, University of Hawaii, UH; J. K. Davies and W. R. F.
Dent, JAC; D. Bockelee-Morvan, MO; D. Jewitt and T. Owen, UH; and
J. Crovisier, H. Rauer, and D. Gautier, MO, report observations of
CO, HCN, H2CO, and CH3OH and the first detections of HNC and (at
sub-mm wavelengths) of CS in comet C/1996 B2 with the James Clerk
Maxwell Telescope at Mauna Kea on Mar. 15.6 and 16.6 UT: "The
integrated line intensities on the antenna temperature scale
(K km/s) were: 0.93 +/- 0.04 [CO J(3-2) at 345 GHz], 3.13 +/- 0.04
[HCN J(4-3) at 354 GHz], 0.54 +/- 0.04 [H2CO 515-414 at 352 GHz],
0.27 +/- 0.03 [H2CO 505-404 at 363 GHz], 0.54 +/- 0.02 [CH3OH
(2,1)-(2,0)A at 304 GHz], 0.73 +/- 0.02 [CH3OH (4,1)-(4,0)A at 307
GHz], 0.23 +/- 0.03 [HNC J(4-3) at 363 GHz], and 0.32 +/- 0.04 [CS
J(7-6) at 343 GHz]. The relative intensities of the methanol
lines suggest a kinetic temperature of 55 +/- 8 K. On Feb. 27.7
and Mar. 11.5, observations of the same lines gave temperatures of
19 and 46 K, respectively. For Mar. 15/16, we derive Q(CO) = 3.2 x
10E28 mol/s, Q(HCN) = 1.6 x 10E26 mol/s, Q(H2CO) = 0.2 x 10E27
mol/s (parent molecule distribution), Q(H2CO) = 1.2 x 10E27 mol/s
(daughter distribution with 10 000-km scale length), Q(CH3OH) = 2.3
x 10E27 mol/s, Q(HNC) = 1.1 x 10E25 mol/s, and Q(CS) = 1.0 x 10E26
mol/s (parent). Assuming a water-production rate of 1 x 10E29 mol/s,
the inferred abundances are 0.32, 0.0016, 0.002 (0.012), 0.023 for
CO, HCN, H2CO parent (daughter), and CH3OH, respectively. The
detection of the unstable species HNC with an abundance ratio
HNC/HCN = 0.07 in the range of that observed in the interstellar
medium (0.004 to 1) should have strong cosmogonical implications."
J. Sarmecanic, University of California at San Diego (UCSD);
T. Lavezzi, University of Minnesota; and M. Fomenkova and B. Jones,
UCSD, report imaging of this comet using the 1.5-m telescope (+
UCSD mid-infrared camera) at Mt. Lemmon. Photometric magnitudes
in a 10" circular aperture (uncertainties 0.1-0.15 mag): Mar.
18.5 UT, [8.7 microns] = -1.1, [11.7 microns] = -2.2, [12.5
microns] = -2.2; Mar. 19.5, [8.7 microns] = -1.3, [11.7 microns] =
-2.5, [12.5 microns] = -2.3, [19.5 microns] = -3.5; Mar. 20.5,
[8.7 microns] = -2.2, [11.7 microns] = -3.3, [12.5 microns] = -3.4,
[19.5 microns] = -4.8. Two dust features are present in all
images: one directed to the west, and the other being a broad
enhancement toward the southeast.
(C) Copyright 1996 CBAT
1996 March 25 (6353) Daniel W. E. Green
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