Electronic Telegram No. 2200
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
CBAT Director:  Daniel W. E. Green; Room 209; Dept. of Earth and Planetary
 Sciences; Harvard University; 20 Oxford St.; Cambridge, MA  02138; U.S.A.
e-mail:  cbat@iau.org; cbatiau@eps.harvard.edu
URL http://www.cfa.harvard.edu/iau/cbat.html


SUPERNOVA 2010ai
     S. Nakano, Sumoto, Japan, reports the discovery by Koichi Itagaki
(Teppo-cho, Yamagata, Japan) of an apparent supernova (mag 16.9) on numerous
unfiltered 15-2 CCD frames (limiting mag 19.5) exposed on Mar. 11.755 UT
using a 0.60-m f/5.7 reflector (+ Bitran BT-214E camera).  The new object is
located at R.A. = 12h59m24s.03, Decl. = +27o59'47".1 (equinox 2000.0), which
is 12" west and 1" south of the center of the apparent host galaxy.
Nothing is visible at this position on his many past frames (including one
taken on Feb. 24.762 with limiting mag 18.5) and on the Digitized Sky Survey.
Itagaki has posted his discovery image at the following website URL:
http://www.k-itagaki.jp/images/psn-anon.jpg.  The following report was
received several hours after tabulated data from Itagaki's report was posted
on the Central Bureau's unconfirmed-objects webpage.

     W. Zheng, University of Michigan; E. Chatzopoulos, University of Texas;
J. Vinko, University of Szeged; R. Quimby, California Institute of
Technology; F. Yuan, D. Chamarro, M. D. Sisson, N. Whallon, C. Akerlof,
and S. B. Pandey, University of Michigan; J. C. Wheeler, University of
Texas; and G. H. Marion, Texas A&M University and University of Texas,
on behalf of the ROTSE collaboration, report the independent discovery of
2010ai at mag about 16.9 in unfiltered images taken on Mar. 8.43 UT
with the 0.45-m ROTSE-IIIb telescope at McDonald Observatory.  The new
object, which was observed again on Mar. 9.49 (at mag about 16.3), 10.34
(mag about 15.9), and 11.19 (mag about 15.6), is located at R.A. =
12h59m24s.00, Decl. = +27o59'47".5 (equinox 2000.0; uncertainty about 1"),
which is 13".8 west and 0".7 south of the center of the nearest galaxy,
SDSS J125925.04+275948.2 in the Coma cluster; a finding chart for the
object can be found at the following website URL:
http://www.rotse.net/rsvp/j125924.0+275948/j125924.0+275948.jpg.
     A spectrum, obtained on Mar. 11.24 with the 9.2-m Hobby-Eberly Telescope
(+ Marcario Low-Resolution Spectrograph) by J. Caldwell, shows 2010ai to be a
normal type-Ia supernova a few days before maximum.  According to SNID
(Blondin and Tonry 2007, Ap.J. 666, 1024), the spectrum of 2010ai best
resembles that of SN 1994D at two days before maximum brightness.  The best
estimation of redshift from SNID is z = 0.014, which is consistent with the
redshift of the nearest galaxy (z = 0.018) in the Coma cluster.  The
photometric measurements are also consistent with a normal type-Ia supernova
a few days before maximum at this redshift.  The rest-frame photospheric
velocity, estimated from the minimum of the Si II 635.5-nm feature, is about
13500 km/s.


NOTE: These 'Central Bureau Electronic Telegrams' are sometimes
      superseded by text appearing later in the printed IAU Circulars.

                         (C) Copyright 2010 CBAT
2010 March 12                    (CBET 2200)              Daniel W. E. Green