[IAUC] CBET 810: 20070117 : SUPERNOVA 2004et IN NGC 6946

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                                                  Electronic Telegram No. 810
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
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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.


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                         (C) Copyright 2007 CBAT
2007 January 17                  (CBET 810)               Daniel W. E. Green