Electronic Telegram No. 3743
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 2013gy IN NGC 1418 = PSN J03421688-0443185
     Further to CBET 3730, H. Kim, W. Zheng, W. Li, and A. V. Filippenko,
University of California at Berkeley; and S. B. Cenko, Goddard Space Flight
Center, report the LOSS discovery of a supernova in NGC 1418 on unfiltered
KAIT images:

 SN       2013 UT       R.A. (2000.0) Decl.      Mag.      Offset
 2013gy   Dec. 6.31    3 42 16.88  - 4 43 18.5   18.0    10".9 E, 32".0 N

A finding chart for the variable has been posted at the following website
URL:  http://astro.berkeley.edu/~zwk/findingchart/PSN_J03421688-04431848.jpg.
The variable was designated PSN J03421688-0443185 when it was posted at the
Central Bureau's TOCP webpage and is here designated SN 2013gy based on the
spectroscopic confirmation reported below.  Additional CCD magnitudes for
2013gy:  Dec. 4.3 UT, [18.5 (KAIT); 7.760, 17.9 (Gianluca Masi, Francesca
Nocentini, and Patrick Schmeer; remotely using a 43-cm telescope near Ceccano,
Italy; position end figures 16s.90, 18".9).

     L. Tomasella, S. Benetti, L. Tartaglia, P. Ochner, A. Pastorello, E.
Cappellaro, M. Turatto, and N. Elias-Rosa, Osservatorio Astronomico di Padova,
Istituto Nazionale di Astrofisica, report that an optical spectrogram (range
340-820 nm; resolution 1.3 nm) of PSN J03421688-0443185 = SN 2013gy, obtained
on Dec. 7.84 UT with the Asiago 1.82-m Copernico Telescope (+ AFOSC), shows it
to be a normal type-Ia supernova.  Adopting for the host galaxy (NGC 1418) a
recessional velocity of 4204 km/s (Catinella et al. 2005, A.J. 130, 1037; via
NED), a good match is found with type-Ia supernovae about 10 days before
B-band maximum light.  An expansion velocity of about 13800 km/s is derived
from the minimum of the Si II 635-nm line.  The Asiago classification spectra
are posted at website URL http://sngroup.oapd.inaf.it; classification was made
via GELATO (Harutyunyan et al. 2008, A.Ap. 488, 383) and SNID (Blondin and
Tonry 2007, Ap.J. 666, 1024).

     J.-J. Zhang, Yunnan Astronomical Observatory (YNAO); and X.-F. Wang,
Tsinghua University, report on an optical spectrogram (range 350-895 nm) of
PSN J03421688-0443185 = SN 2013gy that was obtained on Dec. 7.68 UT with the
2.4-m telescope (+ YFOSC) at the LiJiang Gaomeigu Station of YNAO.  The
spectrum is consistent with a very young type-Ia supernova.  Cross-correlation
with a library of supernova spectra using the "Supernova Identification" code
(SNID; Blondin and Tonry 2007, Ap.J. 666, 1024) shows that 2013gy matches with
SN 2007bm at 11 days before maximum brightness.  Adopting for the host galaxy
(NGC 1418) a recession velocity of 4204 km/s (Catinella et al. 2005, A.J. 130,
1037), they measure the velocity of the Si II 635.5-nm absorption feature to
be about 14500 km/s, and a velocity of the Ca II infrared triplet absorptions
to be about 15200 km/s.  A minor absorption can be seen at 625.0 nm, which
could be due to C II 658.0-nm at a velocity of 15300 km/s.

     K. Takaki, Y. Moritani, and K. S. Kawabata, Hiroshima University; and M.
Yamanaka, Kyoto University, obtained a low-resolution optical spectrogram
(range 480-900 nm) of PSN J03421688-0443185 = SN 2013gy on Dec. 8.5 UT with
the 1.5-m Kanata telescope (+ HOWPol) at the Higashi-Hiroshima Observatory.
A comparison with a library of supernova spectra using GELATO (Harutyunyan et
al. 2008, A.Ap. 488, 383) suggests that the spectrum is consistent with that
of a young type-Ia supernova about a week before maximum.  The best match is
with SN 1994D at 10 days before B-band maximum.  After correction of the
recession velocity of the host galaxy, it exhibits an absorption line of Si
II 635.5-nm at 608 nm, which corresponds to a line velocity of -13000 km/s.


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

                         (C) Copyright 2013 CBAT
2013 December 9                  (CBET 3743)              Daniel W. E. Green