Electronic Telegram No. 237
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)
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COMET 73P/SCHWASSMANN-WACHMANN
     Z. Sekanina, Jet Propulsion Laboratory, provides search
ephemerides for companion nuclei potentially surviving since 1995.
The predictions are based on his new model for the comet's
fragmentation sequence and hierarchy.  Fragment E, observed in
Aug.-Dec. 1996 (referred to as component B in MPC 28339 and 28917)
and Nov.-Dec. 2000 (IAUC 7534; MPC 41633 and 41824), separated
from the parent nucleus at the time of onset of the major outburst
around 1995 Sept. 6-7, or 16 days before perihelion.  Fragment F,
observed in Nov.-Dec. 2000 (denoted component B in MPC 41633 and
41824) and July-Dec. 2001 (denoted component B in MPC 43446-43447
and in Boehnhardt et al. 2002, Earth, Moon, Planets 90, 131),
separated from a precursor to the primary fragment C at the time
of onset of the follow-up outburst, around 1995 Nov. 2-3, or 41
days after perihelion.  A third potentially surviving fragment, B,
was apparently observed only in 1995-96 (MPC 26211, 26444-26445,
26599, and 26610-26611).  Its separation from component C in
2005-2006 is expected to be only a little greater than that of
fragment F from C.  Observing conditions will gradually improve
until mid-May 2006, when inert fragments down to 80 m across
should be detectable (with the comet passing only about 0.05 AU
from the earth) and the separation from component C will reach
about 25 degrees for component E and about 8 degrees for component
F.  For more details and extended ephemerides, the reader is
referred to a paper in the forthcoming October issue of the
International Comet Quarterly (Sekanina 2005, Int. Comet Q. 27,
224).  An ephemeris for component C was published in the 2005
Comet Handbook.  The predicted separation distances, S (in
minutes of arc), from component C and position angles, P (in
degrees), in the coming weeks are shown below for equinox J2000.0.

             Fragment E      Fragment F
2005 TT      S       P       S       P
              ,       o       ,       o
Sep. 27     11.8   290.8     4.6   290.7
Oct.  7     12.9   291.9     5.0   291.8
     17     14.3   292.9     5.5   292.8
     27     15.8   293.8     6.1   293.8
Nov.  6     17.6   294.6     6.7   294.6
     16     19.7   295.4     7.5   295.4
     26     22.1   296.0     8.4   296.1
Dec.  6     25.1   296.6     9.5   296.6
     16     28.6   297.0    10.7   297.1
     26     32.9   297.4    12.3   297.5


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

                         (C) Copyright 2005 CBAT
2005 September 30                (CBET 237)               Daniel W. E. Green