[IAUC] CBET 818: 20070123 : SUPERNOVAE 2007N AND 2007O

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                                                  Electronic Telegram No. 818
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 2007N AND 2007O
     Further to IAUC 8798, N. Lee and W. Li report the LOSS/KAIT discovery
of an apparent supernova (mag 17.3) on an unfiltered KAIT image obtained
on Jan. 21.52 UT:  SN 2007N is located at R.A. = 12h49m01s.25, Decl. =
-9o27'10".2 (equinox 2000.0), which is 4".3 west and 14".3 north of the
center of MCG -01-33-12.  Nothing was visible at this location on a KAIT
image taken on 2006 Dec. 30.54 (limiting mag 19.0).
     Lee and Li also report the LOSS/KAIT discovery of another apparent
supernova (mag 16.8) on an unfiltered KAIT image obtained on Jan. 21.60
UT:  SN 2007O is located at R.A. = 14h56m05s.18, Decl. = +45o24'16".9
(equinox 2000.0), which is 8".2 east and 1".5 south of the center of UGC
9612.  Nothing was visible at this location on a KAIT image taken on 2006
July 5.23 (limiting mag 19.5).
     J. M. Silverman, R. J. Foley, and A. V. Filippenko, University of
California, Berkeley, report that inspection of CCD spectra (range 440-900
nm), obtained on Jan. 22 UT with the Keck II 10-m telescope (+ DEIMOS),
shows that 2007N and 2007O are type-Ia supernovae.  SN 2007N appears
similar to SN 1991bg (Filippenko et al. 1992, A.J. 104, 1543) at one day
after maximum brightness, although the spectrum does not go to
sufficiently short wavelengths to see the Ti II trough that is
characteristic of 1991bg-like supernovae.  SN 2007O has a spectral-feature
age (Riess et al. 1997, A.J. 114, 722) of 1 +/- 2 days past maximum
brightness.  Removing the recession velocities of 3750 km/s (from narrow
absorption lines) and 10900 km/s (from narrow emission lines), the minimum
of the Si II 635.5-nm feature is found to be blueshifted by 11200 and
10000 km/s, respectively.
     A. Harutyunyan, S. Benetti, I. Agnoletto, M. Turatto, and E.
Cappellaro, Istituto Nazionale di Astrofisica, Osservatorio Astronomico di
Padova; F. Ghinassi, Telescopio Nazionale Galileo (TNG); and S.
Taubenberger, Max-Planck Institut fuer Astrophysik, Garching, report that
a spectrum of 2007O, obtained on Jan. 23.21 UT with the 3.5-m TNG (+
DOLORES; range 328-800 nm, resolution 1.2 nm), shows it to be a type-Ia
supernova near maximum light.  The spectrum closely resembles that of
2003du (Stanishev et al. 2007, A.Ap., submitted) at 1 day before maximum
light.  Adopting a recession velocity of 10856 km/s (Sloan Digital Sky
Survey "Data Release 4" obtained on 2005 August 17, via NED), the
expansion velocity derived from the Si II line (635.5 nm) is about 9900
km/s.
     V. Stanishev, Physics Department, Stockholm University; and A.
Harutyunyan and S. Benetti, Istituto Nazionale di Astrofisica,
Osservatorio Astronomico di Padova, report that a spectrum of 2007N,
obtained on Jan. 23.21 UT with the Nordic Optical Telescope (+ ALFOSC;
range 350-910 nm) by T. Pursimo and H. Uthas, shows it to be a
1991bg-like type-Ia supernova around maximum light.  The spectrum is
similar to that of SN 1991bg around maximum (Gomez et al. 1996, A.J.
112, 2094) and can be seen at the following World Wide Web URL:
http://www.physto.se/~vall/sne_classified.html.  Notably, SN 2007N
has much stronger and a significantly-more-blueshifted Ca II infrared
triplet line than did 1991bg.  The O I 777-nm absorption is also
stronger.  A narrow interstellar Na I 589.3-nm absorption is detected
at the redshift of the host galaxy (v = 3861 km/s; Theureau et al.
2005, A.Ap. 430, 373) with an equivalent width of about 0.11 nm.  The
blueshift of the Si II line (635.5 nm) minimum is about 10800 km/s.


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                         (C) Copyright 2007 CBAT
2007 January 23                  (CBET 818)               Daniel W. E. Green