Electronic Telegram No. 3635
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 2013ex IN NGC 1954
     J. Brimacombe, Coral Towers Observatory, Cairns, Australia; J. L. Prieto,
Princeton University; K. Z. Stanek, B. J. Shappee, C. S. Kochanek, T. W.-S.
Holoien, J. Jencson, U. Basu, and J. F. Beacom, Ohio State University; D.
Szczygiel and G. Pojmanski, Warsaw University Observatory; and M. Dubberley,
M. Elphick, S. Foale, E. Hawkins, D. Mullens, W. Rosing, R. Ross, and Z.
Walker, Las Cumbres Observatory, report the discovery of an apparent supernova
on images obtained with the double 14-cm "Brutus" telescope at Haleakala,
Hawaii, in the course of the All-Sky Automated Survey for SuperNovae (ASAS-SN).

 SN       2013 UT       R.A. (2000.0) Decl.       V        Offset
 2013ex   Aug. 19.62   5 32 46.62  -14 02 45.4   15.6    24".7 W, 60".6 N

Nothing is visible at this position (limiting V mag 17) on images obtained
on Aug. 14 and earlier, though the variable is seen weakly in images obtained
on Aug. 17 (noting that there are strong residuals in subtractions due to a
nearby bright star).  The discovery image and a stacked confirming image by
Brimbacombe, from four 900-s images taken on Aug. 20.77 UT with a 41-cm RCOS
telescope (+ infrared filter, approximating the I band), are posted at URL
http://www.astronomy.ohio-state.edu/~assassin/followup/ASASSN-13cc.jpg.  The
type-Ia supernova 2010ko (CBETs 2569, 2575) and the type-II supernova 2011fi
(CBETs 2800, 2815) also appeared in NGC 1954.

     V. Pandya, S. W. Jha, C. McCully, and B. Patel, Rutgers University;
Y. Camacho, Lehigh University; and P. Vaisanen, Southern African Large
Telescope (SALT) and South African Astronomical Observatory, report that a
spectrogram (range 375-920 nm) of SN 2013ex, taken on Aug. 21.2 UT with the
SALT (+ RSS), shows it to be a type-Ia supernova near maximum light.  Cross-
correlation with a library of supernova spectra using the "Supernova
Identification" code (SNID; Blondin and Tonry 2007, Ap.J. 666, 1024) yields a
best match to the normal type-Ia supernova 2007F at two days before maximum
light, and other good template matches range in phase from about -8 to +3
days past maximum.  Adopting a recession velocity of 3129 km/s for NGC 1954
(Springob et al. 2005, Ap.J. Suppl. 160, 149; via NED) yields a supernova
expansion velocity of 10600 km/s, measured via the minimum of the Si II (rest
635.5 nm) line.


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      superseded by text appearing later in the printed IAU Circulars.

                         (C) Copyright 2013 CBAT
2013 August 22                   (CBET 3635)              Daniel W. E. Green