[IAUC] CBET 2785: 20110809 : SUPERNOVA 2011ek; SUPERNOVA 2011em IN NGC 5164 = PSN J13271319+5529174

[quai en eps.harvard.edu]

                                                  Electronic Telegram No. 2785
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
CBAT Director:  Daniel W. E. Green; Hoffman Lab 209; Harvard University;
 20 Oxford St.; Cambridge, MA  02138; U.S.A.
e-mail:  cbatiau en eps.harvard.edu (alternate cbat en iau.org)
URL http://www.cbat.eps.harvard.edu/index.html
Prepared using the Tamkin Foundation Computer Network


SUPERNOVA 2011ek; SUPERNOVA 2011em IN NGC 5164 = PSN J13271319+5529174
     S. Nakano, Sumoto, Japan, reports the discovery by Masaki Tsuboi
(Kuchita-minami, Asakita-ku, Hiroshima, Japan) of an apparent supernova (mag
16.8) on unfiltered CCD frames (limiting mag 17.9) taken on Aug. 4.533 UT
using a 0.30-m f/5.3 reflector (+ ST-2000XM camera).  The new object, which
was designated PSN J13271319+5529174 when posted on the Central Bureau's
TOCP webpage and is here designated SN 2011em based on the spectroscopic
report below, is located at R.A. = 13h27m13s.19, Decl. = +55d29'17".4
(equinox 2000.0), which is 11".2 east and 3".4 north of the center of NGC
5164.  Nothing is visible at this position on the Digitized Sky Survey
(limiting red mag 19 or fainter).  Additional unfiltered CCD magnitudes for
2011em:  2011 June 28.647, [18.0 (Tsuboi); July 23.579, 17.8 (Tsuboi);
Aug. 5.45, 16.0 (Koichi Itagaki, Teppo-cho, Yamagata, Japan; 0.60-m reflector;
position end figures 13s.21, 17".4; communicated by Nakano); 6.483, 16.6
(Tsuboi); 7.133, 16.6 (Joseph Brimacombe, Cairns, Australia; position end
figures 13s.25, 16".9); 8.493, 16.7 (Tsuboi).  The discovery image was posted
at URL http://www42.tok2.com/home/hiroten/astrophoto/NGC5164110804-01.jpg.
Itagaki's image is posted at URL http://www.k-itagaki.jp/images/5164.jpg.
Brimacombe's image is at http://www.flickr.com/photos/43846774@N02/6019928389/.

     K. S. Kawabata, Hiroshima University; H. Minamoto, Fukuyama Senior High
School; and M. Yamanaka, Hiroshima University, obtained low-resolution optical
spectra of PSN J02254889+1832000 = SN 2011ek (cf. CBET 2783) and of PSN
J13271319+5529174 = SN 2011em on Aug. 6.8 and 6.5 UT, respectively, with the
1.5-m Kanata telescope at Higashi-Hiroshima Observatory.  Both spectra show
broad absorption features of Si II 597.2- and 615.5-nm lines and the 'W'-
shaped S II 546.8= and 564.0-nm lines.  The silicon lines show blueshifts
of -11500 and -15000 km/s for 2011em and 2011ek, respectively.  The shallow
Si II 597.2-nm and Ca II infrared-triplet absorptions in 2011em suggest that
it is a type-Ia supernova, a few days before or around maximum brightness.
The strong Si II 597.2-nm, O I 777.3-nm, and Ca II infrared-triplet
absorptions in 2011ek suggest that this is a supernova-1991bg-like, faint
type-Ia supernova before maximum brightness.


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

                         (C) Copyright 2011 CBAT
2011 August 9                    (CBET 2785)              Daniel W. E. Green