Electronic Telegram No. 3087
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@eps.harvard.edu (alternate cbat@iau.org)
URL http://www.cbat.eps.harvard.edu/index.html
Prepared using the Tamkin Foundation Computer Network


SUPERNOVA 2012bt IN IC 4674 = PSN J18081305-6223542
     G. Pignata, M. Cifuentes, Y. Apostolovski, and M. Vidal, Universidad
Andres Bello; J. Maza, M. Hamuy, R. Antezana, L. Gonzalez, F. Carrasco, R.
Cartier, F. Forster, S. Silva, P. Sanchez, C. Hervias, and R. Ramirez,
Universidad de Chile; F. Aros, Pontificia Universidad Catolica de Chile; B.
Conuel, Wesleyan University; G. Folatelli, IPMU, University of Tokyo; and D.
Reichart, K. Ivarsen, J. Haislip, A. Crain, D. Foster, M. Nysewander, and A.
LaCluyze, University of North Carolina at Chapel Hill, on behalf of the CHASE
project (which is part of the Millennium Center for Supernova Science
collaboration), report the discovery of an apparent supernova (magnitude
approximately 16.5) on an unfiltered image taken on Mar. 7.30 UT with the
0.41-m 'PROMPT 1' telescope located at Cerro Tololo.  The new object is
located at R.A. = 18h08m13s.05 +/- 0".2, Decl. = -62o23'54".2 +/- 0".2
(equinox 2000.0), which is about 0".2 east and 10".8 south of the center of
the galaxy IC 4674.  Nothing is visible at this position on an image from
the SuperCOSMOS Sky Survey taken in 1976 (limiting mag 22).  The variable was
designated PSN J18081305-6223542 when it was posted at the Central Bureau's
TOCP webpage and is here designated SN 2012bt based on the spectroscopic
confirmation reported below.  Additional magnitudes for 2012bt (assumed
unfiltered CCD unless noted otherwise):  Feb. 12.36, [18.5 (CHASE); Mar.
10.26, 16.2 (CHASE); 24.699, 17.3 (Joseph Brimacombe, Cairns, Australia;
41-cm RCOS telescope + STL6K camera + infrared filter, wavelength range >
700 nm; position end figures 13s.10, 53".8; image posted at website URL
http://www.flickr.com/photos/43846774@N02/7012499211/); Apr. 1.786, 19.7
(Brimacombe; position end figures 13s.12, 53".8; red magnitude specified);
2.738, 18.7 (Brimacombe; infrared filter; position end figures 13s.15, 53".5).

     N. Morrell, Las Campanas Observatory; P. Lopez and P. Lira, Universidad
de Chile; G. Pignata and F. Bufano, Universidad Andres Bello, report that an
optical spectrogram (range 370-910 nm) of PSN J18081305-6223542 = SN 2012bt,
obtained on Mar. 29.37 UT with the du Pont 2.5-m telescope (+ WFCCD) at Las
Campanas Observatory, shows it to be a type-Ic supernova.  Using a recession
velocity of 4314 km/s for IC 4674 (Mathewson et al. 1992, Ap.J. Suppl. 81,
413; via NED), GELATO (Harutyunyan et al. 2008, A.Ap. 488, 383; publicly
available at https://gelato.tng.iac.es) indicates that the best matches for
this spectrum are with spectra of the type-Ic supernova 2004aw (Taubenberger
et al. 2006, MNRAS 371, 1459) at one month after the maximum light.


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

                         (C) Copyright 2012 CBAT
2012 April 19                    (CBET 3087)              Daniel W. E. Green