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IAUC 8872: P/2007 R5 = 1999 R1 = 2003 R5 (SOHO); C/2007 O1

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IAUC number

                                                  Circular No. 8872
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://www.cfa.harvard.edu/iau/cbat.html  ISSN 0081-0304
Phone 617-495-7440/7244/7444 (for emergency use only)

P/2007 R5 = 1999 R1 = 2003 R5 (SOHO)
     Continuing the remarks on IAUC 8871, regarding the past
uncritical assumption that this object is a comet, the 'Kracht II'
group has no known association with any comet or meteor streams,
nor has there been any obvious tail or coma observed at any of the
apparitions of this much smaller group of objects -- unlike the
cases involving the Marsden and 'Kracht I' groups of SOHO objects,
which have been linked to comet 96P and at least two meteor streams
(e.g., Sekanina and Chodas 2005, Ap.J. Suppl. 161, 551), and the
Kreutz sungrazers.  An analysis of the images of 1999 R1, 2003 R5,
and 2007 R5 by M. Knight (University of Maryland) suggests that the
expansion of the C2 images (which have a scale of 11".8/pixel) as
it brightens may be an indication of coma material (the object
remains pointlike in C3 images, with a scale of 56"/pixel), and his
analysis of the light curves for each apparition is suggestive more
of a cometary light curve than an asteroidal light curve (though
asteroidal photometric behavior at such high phase angles and small
solar elongations has not been observed previously); peaks in
brightness occurred a few hours after perihelion each time:  near
mag 6 on 1999 Sept. 5.1 and 2003 Sept. 8.4, and near mag 5.5 on
Sept. 11.0 UT (and the magnitude tabulated on IAUC 8871 is from
Knight).  The images of 2007 R5 show it fading rapidly and
disappearing around Sept. 12.3 as it made its turn to move toward
superior conjunction with the sun after perihelion.  According to K.
Battams, both the 1999 and 2003 objects appeared from behind the C2
occulter and "started pretty much as point sources" (perhaps 2
pixels in diameter):  as they crossed the C2 field-of-view, the
objects each "grew in size and brightness at a very steady rate,
but always retaining a well-defined edge (i.e., not diffuse)"; at
the right-hand edge of the C2 field-of-view, the object images
"were probably 4-5 pixels across and 5-6 pixels 'tall' and
generally 'rounded'".

     S. Nakano, Sumoto, Japan, has identified this comet (cf. IAUC
8858) with an asteroidal object designated 2006 GA_38 and observed
on 2006 Apr. 2 by the LONEOS project and on Apr. 9 by the Catalina
Sky Survey; revised hyperbolic osculating orbital elements appear
on MPC 60282.

                      (C) Copyright 2007 CBAT
2007 September 18              (8872)            Daniel W. E. Green

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