Central Bureau for Astronomical Telegrams
IAUC 6591: C/1995 O1
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Circular No. 6591
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Mailstop 18, 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)
URL http://cfa-www.harvard.edu/cfa/ps/cbat.html
Phone 617-495-7244/7440/7444 (for emergency use only)
COMET C/1995 O1 (HALE-BOPP)
G. Narayanan, Steward Observatory; H. M. Butner, Submillimeter
Telescope Observatory (SMTO); J. McMullin, National Radio
Astronomical Observatories; and D. Muders, SMTO, report
observations of HCO+ and CO with the 10-m Heinrich Hertz Telescope
on Mar. 5 and 9: "The J(3-2) line of HCO+ at 267.6 GHz was detected
on Mar. 5 with a main-beam temperature of 0.94 +/- 0.044 K, and a
line area of 3.52 +/- 0.08 K km sE-1. The HCO+(3-2) spectrum shows
a slight asymmetry with a red wing. The J(4-3) line of HCO+ at
356.7 GHz was observed on Mar. 9 with a main-beam temperature of
1.18 +/- 0.057 K and a line area of 3.52 +/- 0.15 K km sE-1. The
HCO+(4-3) spectrum shows a redward wing that is offset by 3.6 km/s
relative to the main line. The intensity of the red wing is 0.17
+/- 0.057 K. The linewidths (FWHM) of the two components are 2.84
+/- 0.14 km/s (main line) and 3.17 +/- 0.89 km/s (red wing). The
CO J(2-1) line at 230.5 GHz was detected on Mar. 5 with a main-beam
temperature of 0.27 +/- 0.021 K and a line area of 0.67 +/- 0.053 K
km sE-1. The column densities of CO and HCO+ are estimated to be
6.1 x 10E14 cmE-2 and 2.7 x 10E12 cmE-2 (assuming a line-excitation
temperature of 40 K and optically thin conditions for the region of
emission of CO and HCO+). We calculate the following production
rates: CO, 1.7 x 10E29 molecules/s; HCO+, 7.0 x 10E26 molecules/s."
J. E. Wink, Institut de Radio Astronomie Millimetrique (IRAM),
Grenoble; D. Bockelee-Morvan, N. Biver, P. Colom, J. Crovisier, E.
Gerard, and H. Rauer, Observatoire de Paris; D. Despois,
Observatoire de Bordeaux; R. Moreno and G. Paubert, IRAM, Granada;
and J. K. Davies and W. R. F. Dent, Joint Astronomy Centre, Hilo,
report the detection of SO2 in comet C/1995 O1 on Mar. 18.3 UT at
the IRAM Plateau de Bure interferometer, using its five antennae in
a single-dish mode: "The SO2 11(1,11)-10(0,10) rotational line at
221.965 GHz was detected with an integrated line area on a TA*
scale of 0.08 +/- 0.01 K km sE-1. Assuming thermal excitation at
80 K, the derived SO2 production rate is about 6 x 10E27
molecules/s. The production rate might be larger if the excitation
of the rotational lines of SO2 is dominated by radiative excitation
of the electronic bands in the ultraviolet. This is the first
detection of SO2 in a comet, one of the sources of SO (Lis et al.,
IAUC 6573). Comparison of observations of SO 6(5)-5(4) 219.949-GHz
and H2S 2(2,0)-2(1,1) 216.710-GHz lines, made simultaneously in
both single-dish and interferometric modes at IRAM on Mar. 13.3,
show that the bulk of SO does not come directly from the nucleus,
in contrast to H2S."
(C) Copyright 1997 CBAT
1997 March 19 (6591) Daniel W. E. Green
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