[IAUC] CBET 899: 20070320 : SUPERNOVAE 2007as AND 2007at

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                                                  Electronic Telegram No. 899
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
M.S. 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
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SUPERNOVAE 2007as AND 2007at
     N. Morrell and G. Folatelli, on behalf of the Carnegie Supernova
Project, report spectroscopic observations (range 343-963 nm) of 2007as
and 2007at obtained on Mar. 19.04 and 19.28 UT, respectively, with the
2.5-m du Pont telescope (+ Boller & Chivens spectrograph) at Las
Campanas Observatory.  The spectrum of 2007as (cf. CBET 888) shows this
to be a type-Ia supernova at a few days before maximum light.  Assuming
the NED recession velocity of 5268 km/s for the host galaxy (Fairall and
Woudt 2006, MNRAS 366, 267), the absorption minimum of the Si II 635.5-nm
doublet indicates an expansion velocity of 13300 km/s, while that of the
Ca II H-and-K doublet corresponds to 23300 km/s, which suggests a young
age for the supernova.
     SN 2007at (cf. CBETs 893, 898) is a type-Ia supernova at about 10
days after maximum light.  Adopting the NED recession velocity of 16262
km/s for the host galaxy (Lauberts and Valentijn 1989, "The Surface
Photometry Catalogue of the ESO-Uppsala Galaxies") the 'superfit'
spectrum-comparison code (Howell et al. 2005, Ap.J. 634, 1190) provides
a good match to the spectrum of SN 1992A at 9 days after maximum light.
The aborption minimum of the Si II 635.5-nm doublet indicates an
expansion velocity of 10700 km/s, and that of the Ca II H-and-K doublet
corresponds to 13000 km/s.


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                         (C) Copyright 2007 CBAT
2007 March 20                    (CBET 899)               Daniel W. E. Green