Electronic Telegram No. 3075
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 2012bk = PSN J13545169-2630464
     [Editor's note:  this text replaces that on CBET 3074 (correction to
designation in title).]
     J. Maza, M. Hamuy, R. Antezana, L. Gonzalez, R. Cartier, F. Forster, S.
Silva, F. Carrasco, P. Sanchez, C. Hervias, and R. Ramirez, Universidad de
Chile; G. Pignata, M. Cifuentes, Y. Apostolovski, and M. Vidal, Universidad
Andres Bello; 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 (mag approximately 16.8) on an
unfiltered image taken on Mar. 25.34 UT with the 0.41-m 'PROMPT 5' telescope
located at Cerro Tololo.  The new object is located at R.A. = 13h54m51s.69
+/- 0".2, Decl. = -26o30'46".4 +/- 0".2 (equinox 2000), which is about 8".2
west and 3".6 north of the center of the presumed host galaxy.  The variable
was designated PSN J13545169-2630464 when it was posted at the Central
Bureau's TOCP webpage and is here designated SN 2012bk based on the
spectroscopic confirmation reported below.  Additional CCD magnitudes for
2012bk:  Feb. 4.29-Mar. 7.15, [19.5 (CHASE; eight stacked 40-s images);
Mar. 14.27, [18.0 (CHASE); 26.25, 16.0 (CHASE); 27.415, 17.3 (Joseph
Brimacombe, Cairns, Australia; remotely using a 51-cm RCOS telescope +
STL11K camera + luminance filter at the New Mexico Skies Observatory near
Mayhill, NM, U.S.A.; position end figures 51s.68, 46"; image posted at
website URL http://www.flickr.com/photos/43846774@N02/7023051949/).

     J. L. Prieto, Princeton University, reports that he obtained an spectrum
(range 370-930 nm) of PSN J13545169-2630464 = SN 2012bk on Mar. 27.22 UT
using the du Pont 2.5-m telescope (+ WFCCD) at Las Campanas Observatory.  The
spectrum shows a blue continuum with several broad absorption features, the
strongest ones at 578, 633, and 657 nm.  The redshift of the host galaxy is
determined from unresolved emission lines in the spectrum that are consistent
with the wavelengths of H-beta, [O III] 500.7-nm, and H-alpha at z = 0.0176.
After correcting the spectrum of the object to the rest wavelength, we find
that the absorption features are consistent with blueshifted He I lines, most
prominently the He I 587.5-nm has the absorption minimum at -10300 km/s.
These properties are consistent with a type-Ib supernova around maximum light
(e.g., Modjaz et al. 2009, Ap.J. 702, 226).


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      superseded by text appearing later in the printed IAU Circulars.

                         (C) Copyright 2012 CBAT
2012 March 29                    (CBET 3075)              Daniel W. E. Green