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IAUC 6364: C/1996 B2

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                                                  Circular No. 6364
Central Bureau for Astronomical Telegrams
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)
Phone 617-495-7244/7440/7444 (for emergency use only)

     A. Dutrey, Institut de Radio Astronomie Millimetrique (IRAM);
D. Despois, Observatoire de Bordeaux; D. Bockelee-Morvan, P. Colom,
N. Biver, J. Crovisier, E. Gerard, and H. Rauer, Observatoire de
Paris; M. Grewing, S. Guilloteau, R. Lucas, R. Neri and J. Wink,
IRAM, report the detection of CH3CN in comet C/1996 B2 on Mar. 26.4
UT at the IRAM Plateau de Bure Interferometer using its four
antennas in a single-dish mode:  "The CH3CN 5(1)-4(1) 91.9853-GHz
and 5(0)-4(0) 91.9871-GHz lines were detected with integrated line
area on a TA* scale of 0.028 +/- 0.004 and 0.025 +/-0.004 K km/s,
respectively.  Assuming a rotation temperature of 80 K, we derive a
CH3CN-production rate of 1.8 x 10E25 mol/s.  For a water-
production rate of 3.5 x 10E29 mol/s (IAUC 6355), the inferred
CH3CN abundance is 5 x 10E-5."
     H. Bohnhardt, Institute for Astronomy and Astrophysics,
University of Munich, reports on CCD observations by O. Barnbandner
and himself made during Mar. 23.90-24.18 UT with the 0.80-m
telescope (+ broadband B, V, and R filters) at the Mt. Wendelstein
Observatory: "After image analysis using adaptive Laplace filtering,
we detected time-variable jets close to the nucleus and shell-like
structures in the sunward coma hemisphere.  The shell structures
are apparently identical with the remnants of old jets from
previous revolutions of the nucleus.  We can identify up to three
generations of signatures from on-going and previous jet activities
in our 3'.6 x 4'.5 field of view:  the actual (0) level with jets
close to the nucleus (up to 2-4 jets at a time, typical extension
of some 10"-40" from the nucleus; curvature mostly counterclockwise,
occasionally also straight, but confined to the sunward coma
hemisphere); another shell level about 1' away from the nucleus in
the coma hemisphere; and a third, weaker shell about 2' away from
the center.  The features described are most likely produced by
dust.  The projected shell expansion velocity was estimated to be
of the order of 250 m/s.  Examples of the coma jets and shells can
be found under http://www.eso.org/educnpubrelns/phot-hya-mar25-hb.html."
     Further selected naked-eye m1, coma-diameter, and tail-length
estimates:  Mar. 27.10 UT, 0.4, about 60', 45 deg (H. Mikuz,
Ljubljana, Slovenia); 27.43, 1.0, 1.0 deg, 70 deg (A. Hale,
Cloudcroft, NM); 28.15, 0.7, -, > 50 deg (M. Tichy, Klet, Czech
Republic); 28.90, 0.5, 45', - (J.-C. Merlin, Le Creusot, France);
29.18, 1.5, 40', 10 deg (C. E. Spratt, Victoria, BC; strong
moonlight); 29.81, 1.3, 40', 20 deg (K. Hornoch, Lelekovice, Czech

                      (C) Copyright 1996 CBAT
1996 March 29                  (6364)            Daniel W. E. Green

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