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IAUC 8799: C/2007 B2; 2004et

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                                                  Circular No. 8799
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://cfa-www.harvard.edu/iau/cbat.html  ISSN 0081-0304
Phone 617-495-7440/7244/7444 (for emergency use only)


COMET C/2007 B2 (SKIFF)
     B. A. Skiff, Lowell Observatory, reports his discovery of a
comet on LONEOS CCD images obtained with the 0.59-m Schmidt
telescope (discovery observation tabulated below), the object
showing a small, slightly fuzzy, strongly condensed coma, perhaps
10" in diameter, with no tail.  Confirming CCD images were taken by
Skiff with the Lowell Perkins 1.8-m telescope, in which 3- and
5-min R-filter exposures show the coma to be strongly concentrated
and essentially circular, with a diameter of 6" (and again no tail).

     2007 UT             R.A. (2000) Decl.       Mag.
     Jan. 23.28763    9 54 55.52   +43 55 31.8   18.1

The available astrometry, the following preliminary parabolic
orbital elements, and an ephemeris appear on MPEC 2007-B39.

     T = 2008 Oct. 11.159 TT          Peri. = 216.688
                                      Node  =  12.989   2000.0
     q = 2.66771 AU                   Incl. =  28.259


SUPERNOVA 2004et IN NGC 6946
     J. Rho, California Institute of Technology, together with T. H.
Jarrett and R. Chevalier, report x-ray emission from SN 2004et (cf.
IAUC 8413) in the spiral galaxy NGC 6946.  The x-ray detection was
serendipitously found using archival Chandra X-ray Observatory data
of three separate pointings, each about 29000 s in length.  For the
location of 2004et, a total of 202, 151, and 158 photons were
detected for the observations on 2004 Oct. 22, Nov. 6, and Dec. 3,
respectively.  The spectrum of the first observation is best fitted
by a thermal model with a temperature of 1.3 keV (lower limit 0.5
keV) and a line-of-sight absorption of 1 x 10**22 cm**-2 [upper
limit 2 x 10**22 cm**-2].  The estimated extinction to the
supernova, A_v = 0.41 mag (Zwitter et al. 2004, IAUC 8413), is
consistent with a foreground atomic-hydrogen column density of 3 x
10**21 cm**-2, corresponding to the lower envelope of the present
x-ray absorption measurements.  The inferred unabsorbed luminosity
(0.4-10 keV) is about 4 x 10**38 erg/s (using a distance of 5.5 Mpc),
which falls into the luminosity range of known x-ray supernovae.
The x-ray hardness ratio declines between the first and last epoch,
consistent with a slight temperature decrease over the time period.

                      (C) Copyright 2007 CBAT
2007 January 24                (8799)            Daniel W. E. Green

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