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IAUC 8562: 2005cu; Mkn 501; C/2005 A1

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                                                  Circular No. 8562
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)

SUPERNOVA 2005cu IN NGC 6754
     L. A. G. Monard, Pretoria, South Africa, reports the discovery
of an apparent supernova (mag about 16.1 +/- 0.2) on unfiltered CCD
images taken July 10.760 UT (and confirmed on July 11.720 at mag
about 15.9 +/- 0.2) with a 0.30-m Schmidt-Cassegrain reflector.
SN 2005cu is located at R.A. = 19h11m24s.51, Decl. = -50o38'28".8
(equinox 2000.0), which is 12" west and 3" north of the nucleus of
NGC 6754.  Nothing is visible at this location on the Digitized Sky
Survey (limiting red mag 20.5) on an image taken on 2005 June
18.100 by Monard (limiting red mag 18.0).

     F. Goebel, Max-Planck-Institut fuer Physik, Munich, on behalf
of the MAGIC collaboration, writes that the 'Imaging Air Cherenkov'
telescope MAGIC at La Palma has observed a gamma-ray flare of the
BL Lac-type active galactic nucleus Markarian 501 during June
30.907-30.950 UT.  The measured integrated flux above 200 GeV
corresponds to approximately 3-4 times the Crab flux.  The observed
energy spectrum extends up to 5 TeV and above.  Follow-up
observations around July 3.92 and 6.92 yielded lower flux levels of
about 1 and 0.5 Crab units, respectively.  Further observations are
scheduled (see http://magic.mppmu.mpg.de/physics/mkn501flare05/),
and simultaneous observations at other wavelengths are encouraged.

     Z. Sekanina, Jet Propulsion Laboratory, reports that
application of a two-parameter version of his comet fragmentation
model to 24 astrometric observations from June 25 to July 9 (MPEC
2005-N18, 2005-N21, and 2005-N55) has shown the companion nucleus
to have separated from the parent comet on 2005 Apr. 23.4 +/- 0.8
TT, being subjected to a differential deceleration of 16.2 +/- 0.6
units of 10**-5 solar attraction.  Solving in addition for a
transverse or normal component of the separation velocity has shown
that it did not exceed 0.1 m/s, while the time of breakup and
deceleration remained nearly the same.  The companion may be
observable for many months, depending on its brightness variations.
The predicted separation distances and position angles of the
companion relative to the primary nucleus (0h TT, equinox 2000.0):
2005 July 9, 12", 203 deg; 29, 20", 200 deg; Aug. 18, 27", 192 deg;
Sept. 7, 33", 179 deg; 27, 36", 165 deg; Oct. 17, 35", 155 deg;
Nov. 6, 33", 150 deg; 26, 31", 148 deg.

                      (C) Copyright 2005 CBAT
2005 July 11                   (8562)            Daniel W. E. Green

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