Central Bureau for Astronomical Telegrams
IAUC 7656: C/2001 A2
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Circular No. 7656
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)
CBAT@CFA.HARVARD.EDU (science)
URL http://cfa-www.harvard.edu/iau/cbat.html ISSN 0081-0304
Phone 617-495-7440/7244/7444 (for emergency use only)
COMET C/2001 A2 (LINEAR)
O. Schuetz, E. Jehin, X. Bonfils, H. Boehnhardt, K. Brooks, A.
Delsanti, O. Hainaut, E. Jourdeuil, P. Leisy, M. Sterzik, and E.
Wenderoth, European Southern Observatory (ESO); J. Helbert, DLR,
Berlin; G. Garradd, Loomberah, N.S.W.; F. Marchis, University of
California at Berkeley; B. Stecklum, TLS-Tautenburg; and G. Tozzi,
Osservatorio Astrofisico di Arcetri, report that an intensive
high-resolution monitoring of the inner coma on June 16-21
indicates that the comet continues to fragment. The images
obtained at ESO (La Silla) in the thermal infrared with the 3.6-m
telescope (+ TIMMI2, N band), and in the optical region with the
3.5-m New Technology Telescope (+ EMMI, R filter) and the ESO/MPG
2.2-m telescope (+ WFI, R filter), show faint companions drifting
away from the principal nucleus (B) in an approximately antisolar
direction. Analysis by Z. Sekanina, Jet Propulsion Laboratory,
shows that all the observations can be satisfied by three
fragments, D, E, and F. The observed offsets (separation from B
and position angle), the fragment identification, and the
instruments used are as follows: June 16.422 UT, 2".8, 212 deg,
D+E+F (TIMMI2); 17.447, 4".6, 215 deg, E+F (TIMMI2); 18.409, 6".7,
222 deg, F (WFI); 18.449, 6".5, 219 deg, F (TIMMI2); 18.456, 6".6,
222 deg, F (EMMI); 19.433, 4".7, 222 deg, D (WFI); 19.433, 7".2,
222 deg, E and/or F (WFI); 19.449, 5".0, 223 deg, D (EMMI); 19.449,
8".5, 223 deg, E and/or F (EMMI); 20.433, 6".1, 231 deg, D (WFI);
20.433, 8".3, 222 deg, E (WFI); 21.437, 11".0, 223 deg, E (TIMMI2);
21.442, 7".2, 231 deg, D (EMMI); and 21.442, 10".6, 222 deg, E
(EMMI). The analysis implies that fragment D separated from B on
June 3.5 +/- 1.8 with a differential nongravitational deceleration
of 17 units (of 10**-5 the solar attraction) and with an initial
velocity of 1.0 +/- 0.1 m/s (approximately normal to the orbit
plane); fragment E on June 9.5 +/- 0.7 with a deceleration of 53
units and a velocity of 0.3 +/- 0.1 m/s; and fragment F on June
11.3 +/- 0.5 with a deceleration of 102 units and a velocity of 0.8
+/- 0.2 m/s. These breakup events apparently triggered another
major outburst (cf. IAUC 7630), reported by visual observers to
have peaked on June 12.
Total-visual-magnitude and coma-diameter estimates: July 1.05
UT, 4.4, 20' (R. Haver, Frasso Sabino, Italy, 10x50 binoculars);
1.71, 4.5, 16' (S. Yoshida, Ibaraki, Japan, 10x24 binoculars);
2.69, 4.7, 10' (M. Mattiazzo, Wallaroo, S. Australia, 7x50
binoculars; moonlight); 3.08, 5.0, 18' (A. Giambersio, Potenza,
Italy, 16x70 binoculars); 3.95, 4.5, 12' (D. V. Fedotov, Kharkov,
Ukraine, 7x50 binoculars); 4.75, 4.8, 20' (Y. Nagai, Yamanashi,
Japan, 12x50 binoculars; moonlight).
(C) Copyright 2001 CBAT
2001 July 5 (7656) Daniel W. E. Green
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