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IAUC 7946: 57P; 2002ec

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                                                  Circular No. 7946
Central Bureau for Astronomical Telegrams
Mailstop 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
IAUSUBS@CFA.HARVARD.EDU or FAX 617-495-7231 (subscriptions)
URL http://cfa-www.harvard.edu/iau/cbat.html  ISSN 0081-0304
Phone 617-495-7440/7244/7444 (for emergency use only)

     Z. Sekanina, Jet Propulsion Laboratory, writes: "Very
preliminary analysis of the relative astrometry of the two
brightest nuclei (cf. MPEC 2002-O10) has been completed,
employing a new computer code recently developed by P. W. Chodas
and myself. The parameters of the standard model for split
comets are now determined with full account of the planetary
perturbations and the nongravitational effects on the principal
nucleus. The results suggest that nucleus B could have broken
off from primary A near perihelion in 1996. If the event had
occurred exactly at perihelion, plausible values for the
nongravitational deceleration (4-8x10**-5 solar attraction, as B
is obviously a persistent companion; cf. Sekanina 1982, Comets,
ed. L. L. Wilkening, pp. 251-287) require that B separated from
A with a reasonably low velocity, whose transverse component
ranged from 0.5 to 1 m/s in the direction opposite the orbital
motion and whose normal component was some 0.4-0.5 m/s toward the
north orbital pole. These solutions are independent of the radial
component of the separation velocity. Similar solutions are also
found for separation times 100 days before and after perihelion,
except that the deceleration then correlates with both the
transverse and radial components. Because of the comet's extremely
low orbital inclination, it is doubtful that the separation
parameters can ever be determined with high accuracy. All examined
solutions yield essentially the same ephemeris, which shows that
the projected separation of B from A will diminish in the coming
weeks. The offsets and position angles are as follows (0h UT):
2002 Aug. 4, 853", 259.1 deg; 14, 814", 259.1; 24, 758", 259.0;
Sept. 3, 694", 258.7; 13, 631", 258.3; 23, 571", 257.7; Oct. 3,
516", 257.0. It is unlikely that companions C-T (cf. IAUC 7935)
are all products of the same event. In particular, C-F were probably
released from A more recently than B was. Some of nuclei M-T may be
fragments of B, but a more complex fragmentation hierarchy is
also possible. Accurate astrometry on existing images and additional
observations may allow one to make more, but not very, definite
statements in the future.''

SUPERNOVA 2002ec IN NGC 5910
     M. Salvo and P. Price, Research School of Astronomy and
Astrophysics, Australian National University (ANU), report that
a spectrum (range 340-920 nm, resolution about 0.4 nm) of
SN 2002ec (cf. IAUC 7937), taken with the ANU 2.3-m telescope
(+ double beam spectrograph) at Siding Spring Observatory on
July 31.43 UT, shows that this object is a Type Ia supernova
close to maximum light.

                      (C) Copyright 2002 CBAT
2002 August 3                  (7946)          Carl W. Hergenrother

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