Copyright © 2009 / 2012 - Alfons Diepvens - all rights reserved.

Back 
http://www.cbat.eps.harvard.edu/iau/cbet/000700/CBET000738.txt


                                        Electronic Telegram No. 738



Central Bureau for Astronomical Telegrams INTERNATIONAL
ASTRONOMICAL UNION M.S. 18, Smithsonian Astrophysical Observatory,
Cambridge, MA 02138, U.S.A. IAUSUBS@CFA.HARVARD.EDU or FAX 617-495-7231
(subscriptions) CBAT@CFA.HARVARD.EDU (science) URL
http://cfa-www.harvard.edu/iau/cbat.html 

COMET C/2006 M4 (SWAN)
Z. Sekanina, Jet Propulsion Laboratory, California Institute of
Technology, writes that a preliminary inspection of the astrometric
observation of C. E. Woodward et al. from Nov. 7 of a detached-coma
feature (cf. IAUC 8772), suggests that this is a compact cluster of
sizable nucleus fragments, released from the primary at the time of a
recent outburst (IAUC 8766). The cluster, rather than a single
fragment, is implied by the feature's reported elongation along the
offset vector, reminiscent of similar episodes experienced recently by
comet 73P's nuclei B, G, and others. Assuming, tentatively, 2006 Oct.
23.9 UT for this event's onset time, the observed offset fits the
modeled separation distance perfectly and leaves a residual of 3 degrees
in the position angle, well within observational errors. The derived
effective differential nongravitational deceleration, (69 +/- 4) x
10**-5 units of the sun's gravitational acceleration, implies that the
cluster is a short-lived phenomenon, observable for a few weeks at the
most. The cluster's predicted separation distances and position angles,
relative to the primary nucleus (0h TT, equinox 2000.0), are: 2006 Nov.
11, 5", 39 deg; Nov. 21, 9", 35 deg; Dec. 1, 13", 31 deg; Dec. 11, 17",
27 degrees.
Visual total-magnitude and coma-diameter estimates (cf. IAUC 8766):
Oct. 25.72 UT, 4.2, -- (M. Meyer, Frauenstein, Germany, naked eye);
26.77, 4.2, 15' (M. Lehky, Pasinovice, Czech Republic, naked eye);
28.76, 4.5, 10' (V. Gonano, Udine, Italy, 10x50 binoculars); 30.75, 5.4,
20' (K. Hornoch, Vohancice, Czech Republic, naked eye); Nov. 1.73, 5.6,
10' (A. Diepvens, Balen, Belgium, 20x50 binoculars); 6.63, 5.8, 5' (V.
Ivanov, Saratov, Russia, 0.11-m reflector); 8.79, 6.4, 6' (J. J.
Gonzalez, Asturias, Spain, 7x50 binoculars); 11.86, 6.5, 9' (J.
Carvajal, Madrid, Spain, 6x30 binoculars); 12.78, 6.3, 10' (Gonano).



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superseded by text appearing later in the printed IAU Circulars.


(C) Copyright 2006 CBAT
2006 November 13 (CBET 738) Daniel W. E. Green