Central Bureau for Astronomical Telegrams
IAUC 8685: 73P
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Circular No. 8685
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)
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Phone 617-495-7440/7244/7444 (for emergency use only)
COMET 73P/SCHWASSMANN-WACHMANN
E. J. Christensen, Lunar and Planetary Laboratory, writes that
four co-added unfiltered 150-s images obtained with the Mt. Lemmon
1.5-m reflector on Mar. 5.4 UT by R. E. Hill -- who was following
up a new fragment of comet 73P found by R. Kowalski from Mar. 4.4
images -- show four additional fragments, all lying along an
extension of the arc from component 'B' to component 'G' (p.a.
approximately 300 deg), and bringing the number of currently
observed components to seven (cf. IAUC 8679). Kowalski's fragment,
designated component 'H', has mag 20.0 and trails fragment 'G' by
approximately 875" (corresponding to T = 2006 June 8.29 TT); it
displays a diffuse 4" coma with no central condensation, slightly
elongated toward p.a. 275 deg. Component 'J', which had been noted
by Hill as cometary, trails component 'G' by approximately 170" (T
= June 8.14), and displays a diffuse 8" coma of mag 19.8 with a
very slight central condensation and a 10" tail toward p.a. 275 deg;
90-s images taken by Christensen on Feb. 24 showed nothing at the
presumed location of 'J'. Component 'K' (at mag 21.7) lies
approximately 611" from fragment 'G' (T = June 8.24) and shows a
diffuse 4" coma with neither central condensation nor tail.
Component 'L' lies approximately 1145" from fragment 'G' (T = June
8.35) and displays a slightly condensed 5" coma of mag 19.8 with a
7" tail toward p.a. 275 deg. For comparison, components 'B' and 'G'
were of mag 14.5 and 17.3, respectively, on Mar. 5.4 (all the Mt.
Lemmon magnitudes being calibrated to V). Christensen searched the
line of variation on the Mar. 5 images, out to 3500" from fragment
'G', but could find no other fragments (limiting mag V
approximately 22.0). Inspection of Kowalski's 120-s images from
Mar. 4 yields no trace of fragments 'J', 'K', and 'L' -- although
the area that should contain these fragments was unfortunately
affected by reflections from a nearby bright star. Four 150-s
unfiltered images taken on Mar. 6.5 show no significant changes in
the morphologies of any of the fragments since the previous night,
and no additional fragments were detected along the line of
variation out to approximately 2880" west-northwest of component 'B'
and to approximately 1580" east-southeast of component 'B'
(limiting mag V approximately 22.0). The new astrometry is
published on MPEC 2006-E32.
Visual total-magnitude estimates of component 'C': Feb. 27.68
UT, 12.3 (S. Yoshida, Ibaraki, Japan, 0.40-m reflector); 28.19,
12.8 (J. J. Gonzalez, Leon, Spain, 0.20-m reflector); Mar. 2.90,
11.7 (A. Baransky, Pylypovychi, Ukraine, 0.36-m reflector); 5.61,
12.1 (Yoshida); 6.32, 11.3 (W. Robledo, Cordoba, Argentina, 0.20-m
reflector); 8.19, 11.9 (Gonzalez). Visual total-magnitude
estimates of component 'B': Feb. 27.68, 14.4 (Yoshida); Mar. 8.20,
13.7 (Gonzalez).
(C) Copyright 2006 CBAT
2006 March 8 (8685) Daniel W. E. Green
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