Electronic Telegram No. 3174
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 2012dn IN PGC 64605 = PSN J20233626-2816434
     Greg Bock, Windaroo, Queensland, Australia, reports the discovery of an
apparent supernova (red mag 16.3) by Stuart Parker (Oxford, Canterbury, New
Zealand) on a 30-s unfiltered CCD exposure taken on July 8.52 UT with a 28-cm
Celestron C11 reflector (+ ST10 camera).  The new object is located at R.A. =
20h23m36s.26, Decl. = -28d16'43".4 (equinox 2000.0; measured by Bock using the
USNO-B and UCAC3 catalogues for reference stars), which is 35" west and 3"
south of the nucleus of the galaxy ESO 462-16 = PGC 64605.  Nothing is visible
at this position on red and infrared images from the Digitized Sky Survey
(limiting red magnitude > 19) or on an unfiltered 30-s image of ESO 462-16
taken by Stuart on 2011 Apr. 1 (limiting red magnitude > 18.0).

     J. T. Parrent, Las Cumbres Observatory Global Telescope (LCOGT) and
Dartmouth College; and D. A. Howell, LCOGT and University of California at
Santa Barbara, report that an optical spectrum (range 350-970 nm) of PSN
J20233626-2816434 = SN 2012dn was obtained on July 10.2 UT with the Gemini
Multi-Object Spectrograph (GMOS) on the 8-m Gemini South telescope.  Cross-
comparisons with a library of supernovae spectra via "Superfit" (Howell et al.
2005, Ap.J. 634, 1190) suggest that 2012dn is a type-Ia supernova
approximately a week before maximum light.  After removal of a host-galaxy
recession velocity of 2958 km/s for PGC 64605, the Si II 635.5-nm absorption
minimum is seen to be blueshifted by 12000 km/s.  In addition, the detection
of a strong C II 657.8-nm absorption feature (blueshifted by 12200 km/s) and
comparisons to pre-maximum spectra of SN 2006gz (Hicken et al. 2007, Ap.J.
669, L17), SN 2007if (Scalzo et al. 2010, Ap.J. 713, L1073), and SN 2009dc
(Yamanaka et al. 2009, Ap.J. 707, L118) suggest that 2012dn is a super-Chandra
event.


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      superseded by text appearing later in the printed IAU Circulars.

                         (C) Copyright 2012 CBAT
2012 July 12                     (CBET 3174)              Daniel W. E. Green