[IAUC] CBET 1048: 20070903 : SUPERNOVA 2007hj IN NGC 7461

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                                                  Electronic Telegram No. 1048
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
M.S. 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
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SUPERNOVA 2007hj IN NGC 7461
     Further to CBET 1034, X. Parisky and W. Li report the discovery of an
apparent supernova on unfiltered KAIT images taken on Sept. 1.32 (at mag
15.9) and 2.30 UT (mag 15.7).  The new object is located at R.A. =
23h01m47s.89, Decl. = +15o35'11".4 (equinox 2000.0), which is 6".7 west
and 14".0 north of the center of NGC 7461.  A KAIT image taken on Aug.
22.34 showed nothing at this location (limiting mag 19.5).
     S. Blondin, R. Kirshner, and P. Challis, Harvard-Smithsonian Center
for Astrophysics, report that a spectrogram (range 350-740 nm) of 2007hj,
obtained by M. Calkins on Sept. 3.28 UT with the F. L. Whipple Observatory
1.5-m telescope (+ FAST), shows it to be a type-Ia supernova around
maximum light.  Cross-correlation with a library of supernova spectra
indicates that 2007hj is most similar to the type-Ia supernova 1992A
(Kirshner et al. 1993, Ap.J. 415, 589) at one day before maximum.  It is
noted, however, that 2007hj is similar to several sub-luminous type-Ia
supernovae, characterized by a strong absorption feature at 580 nm due to
Si II.  Adopting a recession velocity of 4274 km/s for the host galaxy
(from The Updated Zwicky Catalog; http://tdc-www.harvard.edu/uzc/), the
maximum absorption in the Si II line (rest 635.5 nm) is blueshifted by
roughly 12800 km/s.  Assuming that the galaxy is in the Hubble flow and
that the supernova suffers negligible extinction, the discovery magnitude
of 15.7 corresponds to an absolute magnitude of roughly -18.2, which
suggests a subluminous event.


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                         (C) Copyright 2007 CBAT
2007 September 3                 (CBET 1048)              Daniel W. E. Green