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IAUC 8545: C/2004 PY_42; C/2005 K2

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                                                  Circular No. 8545
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://cfa-www.harvard.edu/iau/cbat.html  ISSN 0081-0304
Phone 617-495-7440/7244/7444 (for emergency use only)

     W. Romanishin, University of Oklahoma; and S. C. Tegler,
Northern Arizona University, report that the centaur-type minor
planet 2004 PY_42 (cf. MPEC 2004-P48, 2004-Q30; MPS 111230), which
was reported as asteroidal when discovered on CCD images taken in
the course of the "Campo Imperatore Near Earth Objects Survey" (A.
Boattini, F. De Luise, and A. Di Paola, 0.60-m f/3 Schmidt
telescope; discovery observation given below), shows a faint
asymmetric coma (R about 21.5), extending 4" to the northwest, in
six co-added 5-min R-band exposures obtained around June 7.4 UT and
in eleven co-added 5-min exposures obtained around June 8.4 with
the 1.8-m Vatican Advanced Technology Telescope.  The additional
astrometry, revised orbital elements (T = 2001 Apr. 24, q = 11.79
AU, e = 0.27, Peri. = 344 deg, Node = 296 deg, i = 19 deg, equinox
2000.0; P = 64.8 yr), and an ephemeris appear on MPEC 2005-M12.

     2004 UT             R.A. (2000) Decl.       Mag.
     Aug. 10.87443   20 46 08.00   -12 00 02.7   19.8

     Z. Sekanina, Jet Propulsion Laboratory, writes:  "Applying a
two-parameter version of my comet fragmentation model to 20
astrometric observations from 2005 June 10-16 (MPEC 2005-M11), I
find the companion nucleus to have separated from the parent comet
on 2005 Apr. 22 +/- 2 and been subjected to a differential
deceleration of 42 +/- 2 units of 10**-5 solar attraction.  Solving
in addition for a transverse or normal component of the separation
velocity yields nearly the same time of breakup and the separation
velocity much lower than 1 m/s.  The companion is a fragment with a
limited lifespan, possibly less than 100 days.  The splitting may
be responsible for the steep light curve and may have facilitated
the comet's discovery on May 19.  However, the apparent flare-up in
early June (IAUC 8540) is not directly related to the described
fragmentation event, a conclusion reached independently by J. A.
Farrell (personal communication).  Searches for the companion in
existing images from late May and early June are encouraged, as
additional data should assist in refining the fragmentation model.
The predicted separation distances and position angles of the
companion relative to the primary (0h TT, equinox 2000.0):  May 20,
4", 266 deg; 25, 7", 276 deg; 30, 11", 9 deg; June 4, 18", 42 deg;
9, 28", 46 deg; 14, 39", 48 deg; 19, 49", 52 deg; 24, 57", 59 deg;
29, 63", 68 deg."

                      (C) Copyright 2005 CBAT
2005 June 17                   (8545)            Daniel W. E. Green

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