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IAUC 8921: (153591) 2001 SN_263; C/2007 Y3-Y9

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                                                  Circular No. 8921
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://www.cfa.harvard.edu/iau/cbat.html  ISSN 0081-0304
Phone 617-495-7440/7244/7444 (for emergency use only)


(153591) 2001 SN_263
     M. C. Nolan and E. S. Howell, Arecibo Observatory; L. A. M.
Benner, S. J. Ostro, and J. D. Giorgini, Jet Propulsion Laboratory;
M. W. Busch, California Institute of Technology; L. M. Carter and
R. F. Anderson, Smithsonian Institution; C. Magri, University of
Maine at Farmington; D. B. Campbell and J. L. Margot, Cornell
University; R. J. Vervack, Jr., Applied Physics Laboratory, Johns
Hopkins University; and M. K. Shepard, Bloomsburg University,
report that Arecibo radar delay-Doppler images (2380 MHz, 12.6 cm),
obtained on 2008 Feb. 12 and 13, show that minor planet (153591) is
a triple system.  Based on range extents at 75-m resolution,
preliminary estimates of average diameters are 2 km, 1 km, and 400
m for the three components.  The orbital separation for the larger
two components is at least 10 km.


COMETS C/2007 Y3-Y9 (SOHO)
     Further to IAUC 8920, additional near-sun comets have been
found on SOHO website images; all were Kreutz sungrazers except for
Marsden-group member C/2007 Y4 and Meyer-group member C/2007 Y8 --
both of which were small and stellar in appearance, reaching mag
about 6.5 (though the latter object brightened extremely fast in
the first hour or two of visibility and became noticeably larger in
that time -- atypical for Meyer-group objects).  K. Battams
suggested the identity of C/2007 Y4 with C/2002 R4 (cf. MPEC 2002-
S35; IAUC 7984), and B. G. Marsden published a linked orbit on MPEC
2008-B49 that suggests an approach to within 0.063 AU of the earth
on 1997 June 14.7 (T = 1997 May 15.2).  C/2007 Y3 was quite diffuse
and small (mag about 7.5).  C/2007 Y5 was quite bright (mag about
5.5) and teardrop-shaped (with a hint of a stubby tail).  C/2007 Y6
was very diffuse (mag about 8) with a hint of a tail.  C/2007 Y7
was tiny and a little diffuse (mag about 8.5).  C/2007 Y9 was quite
diffuse, only reaching mag 7.5.

 Comet        2007 UT       R.A.(2000)Decl.   Inst.  F    MPEC
 C/2007 Y3    Dec. 21.104   17 58.9  -25 14   C2     SY   2008-B49
 C/2007 Y4         21.754   18 03.4  -24 07   C2     RK   2008-B49
 C/2007 Y5         22.571   18 13.9  -28 25   C3     AK   2008-B49
 C/2007 Y6         26.338   18 23.2  -25 00   C2     SY   2008-B49
 C/2007 Y7         26.688   18 25.0  -24 47   C2     HS   2008-B49
 C/2007 Y8         28.079   18 25.6  -22 10   C2     RK   2008-B61
 C/2007 Y9         28.638   18 37.4  -26 06   C3     RM   2008-B61

                      (C) Copyright 2008 CBAT
2008 February 13               (8921)            Daniel W. E. Green

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