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IAUC 8926: COMET C/2008 A3 (SOHO); C/2008 D1, C/2008 D2, C/2008 D3, C/2008 D4

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                                                  Circular No. 8926
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)


COMET C/2008 A3 (SOHO)
     Further to IAUC 8923, an additional tiny, very faint (mag
about 7.5) comet was found on SOHO website images that is a member
of the Marsden group ("discovery" observation tabulated below);
according to K. Battams, it may have been "borderline diffuse", and
it maintained a very constant brightness level until quite near the
end, when it started to fade.  R. Kracht suggested the identity of
C/2008 A3 with C/2002 R1 (cf. IAUC 7969, MPEC 2002-R57), and B. G.
Marsden published a linked orbit on MPEC 2008-B61 that yields T =
1997 Apr. 19.0 for its previous (unobserved) perihelion passage.

 Comet        2008 UT       R.A.(2000)Decl.   Inst.  F    MPEC
 C/2008 A3    Jan. 15.588   19 52.2  -20 39   C2     RK   2008-B61


COMETS C/2008 D1, C/2008 D2, C/2008 D3, C/2008 D4 (STEREO)
     K. Battams and K. Baldwin have reported measurements, reduced
and analyzed by B. G. Marsden, for four Kreutz-sungrazing comets
found on images obtained with NASA's new "Solar-Terrestrial
Relations Observatory" (STEREO), which involves two satellites
ultimately to be located 45 deg ahead (STEREO-A) and 45 deg behind
(STEREO-B) the earth in its orbit.  The SECCHI suite of instruments
on each satellite contains two coronagraphs ('COR2' having bandpass
650-750 nm and resolution 15"/pixel) and a "Heliospheric Imager"
consisting of two telescopes ('HI1' having bandpass 650-750 nm and
resolution 35"/pixel).  The tabulated "discovery" observations
below are given in the same format as used for the SOHO comets (see
above); the 'C' under instrumentation denotes the 'COR2' instrument
on both STEREO-A and -B, while the 'HI' flag denotes the 'HI1-A'
instrument only.  C/2008 D1, C/2008 D2, and C/2008 D4 were very
faint (mag about 10-11 for the first and third objects, and about 9
for the second) and diffuse.  C/2008 D3 was of mag perhaps 7 with a
thin, faint tail in HI1-A images, and brighter (mag perhaps 3) with
a thin tail in COR2 images; this is the first near-sun comet to
have an orbit determined (cf. MPEC 2008-E58) using astrometry from
two well-separated spacecraft (now 0.76 AU apart).

 Comet        2008 UT       R.A.(2000)Decl.   Inst.  F    MPEC
 C/2008 D1    Feb. 16.822   23 43.4  - 5 01   HI     AW   2008-E58
 C/2008 D2         19.461   23 55.6  - 4 05   HI     AW   2008-E58
 C/2008 D3         20.294    0 14.0  - 4 49   HI/C   AW   2008-E58
 C/2008 D4         20.933   23 58.9  - 3 23   HI     RK   2008-E58

                      (C) Copyright 2008 CBAT
2008 March 6                   (8926)            Daniel W. E. Green

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