[IAUC] CBET 1901: 20090810 : SUPERNOVA 2009ia

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                                                  Electronic Telegram No. 1901
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
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SUPERNOVA 2009ia
     J. Vinko, University of Texas; F. Yuan, University of Michigan; H.
Marion, University of Texas and Texas A&M University; R. Quimby, California
Institute of Technology; D. Chamarro, M. D. Sisson, and C. Akerlof,
University of Michigan; and J. C. Wheeler and E. Chatzopoulos, University of
Texas, on behalf of the ROTSE collaboration, report the discovery of a
type-Ia supernova (mag about 17.5) in unfiltered CCD images taken on July
22.25 UT with the 0.45-m ROTSE-IIIb telescope at McDonald Observatory.  The
transient, located at R.A. = 17h26m11s.25, Decl. = +59o18'31".3 (equinox
2000.0; uncertainty < 1"), is 0".2 east and 0".2 north of the center of the
galaxy SDSS J172611.22+591831.1 (z = 0.027, as measured by Sloan Digital Sky
Survey).  SN 2009ia was discovered by subtracting a reference image built
from images taken in August 2007.  A finding chart of 2009ia is posted at
URL http://www.rotse.net/rsvp/j172611.3+591831/j172611.3+591831.jpg.
An optical spectrum, obtained on Aug. 1.22 at McDonald Observatory with the
9.2-m Hobby-Eberly Telescope (+ Marcario Low-Resolution Spectrograph) by
M. Shetrone, shows that 2009ia is a type-Ia supernova, but the spectrum looks
peculiar.  There is a strong, narrow H-alpha emission line superimposed on
the supernova spectrum, which is consistent with the host galaxy, being a
strong H-alpha emitter.  The SiI I 635.5-nm and 580.0-nm features are both
weak, suggesting a pre-maximum phase; their ratio is R(Si II) = 0.4, which
is higher than the usual value of 0.1-0.3 for normal type-Ia events close
to maximum light (Benetti et al. 2004, MNRAS 348, 261).  The O I 777-nm
feature is not detected.  The Ca II infrared triplet is present but weak.
According to the SuperNova IDentification (SNID) code, the spectrum most
resembles those of SNe 2003du and 2002er at roughly 10 days before maximum,
assuming a redshift of z = 0.03, which is consistent with that of the host
galaxy.  The ROTSE unfiltered light curve, however, does not show significant
brightening after Aug. 1, thus, it does not support the spectroscopic age
determination.  The expansion velocity, calculated from the absorption
minimum of the Si II 635.5-nm line, after correcting for host-galaxy
redshift, is 11000 km/s.


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                         (C) Copyright 2009 CBAT
2009 August 10                   (CBET 1901)              Daniel W. E. Green