[IAUC] CBET 3406: 20130207 : SUPERNOVA 2013S = PSN J03353029+3816597

Mie Feb 6 18:28:17 ART 2013

                                                  Electronic Telegram No. 3406
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 en eps.harvard.edu (alternate cbat en iau.org)
URL http://www.cbat.eps.harvard.edu/index.html
Prepared using the Tamkin Foundation Computer Network


SUPERNOVA 2013S = PSN J03353029+3816597
     Li Zhou, Xiaofeng Wang, and Juncheng Chen, Tsinghua University (THU);
and Tianmeng Zhang and Xu Zhou, National Astronomical Observatories of China
(NAOC), report the discovery of an apparent supernova (mag 16.1) on unfiltered
CCD images taken on Jan. 25.60 UT using the 0.6-m NAOC schmidt telescope in
the course of the THU-NAOC Transient Survey (TNTS).  The new object is
located at R.A. = 3h35m30s.29, Decl. = +38d16'59".3 (equinox 2000.0), which is
slightly northeast of the center of the galaxy 2MASX J03353030+3816593.
Nothing is visible at this position on a Digitized Sky Survey image from the
Palomar Sky Survey.  Additional approximate TNTS magnitudes for the variable:
2012 Dec. 30, [20.0; 2013 Feb. 2, 15.9.  The TNTS images are posted at website
URL http://www.thca.tsinghua.edu.cn/~wangxf/TNTS/PSNJ03353029+3816597.jpg.
The variable was designated PSN J03353029+3816597 when it was posted at the
Central Bureau's TOCP webpage and is here designated SN 2013S based on the
spectroscopic confirmation reported below.

     Tianmeng Zhang, National Astronomical Observatories of China (NAOC);
Xiaofeng Wang, Tsinghua University, report on an optical spectrogram (range
380-860 nm) of PSN J03353029+3816597 = SN 2013S that was obtained on Feb.
4.80 UT with the 2.16-m telescope (+ BFOSC) at the Xinglong Station of the
NAOC.  The spectrum is consistent with a type-Ia supernova at around maximum
light.  Cross-correlation with a library of supernova spectra using the
"Supernova Identification" code (SNID; Blondin and Tonry 2007, Ap.J. 666,
1024) shows that 2013S matches with SN 1999aa at +3 days.  Adopting a
redshift of 0.0186 from the 2MASS Redshift Survey (Huchra et al. 2012, Ap.J.
Suppl. 199, 26) for the presumed host galaxy (2MASX J03353030+3816593), they
measure the velocity of the Si II 635.5-nm absorption feature to be about
10000 km/s.

    P. Ochner, A. Pastorello, S. Benetti, E. Cappellaro, L. Tomasella, and
M. Turatto, Osservatorio Astronomico di Padova, Istituto Nazionale di
Astrofisica, report that optical spectroscopy (range 340-800 nm; resolution
0.8 nm), obtained on Feb. 5.80 UT with the Asiago 1.22-m Galileo Telescope (+
Boller & Chivens spectrograph), shows that PSN J03353029+3816597 = SN 2013S
is most likely a peculiar type-Ia supernova.  Adopting for the host galaxy
(2MASX J03353030+3816593) the redshift z = 0.018576 (Huchra et al. 2012,
Ap.J. Suppl. 199, 26; via NED), the best match is obtained with SN 2009dc
(Taubenberger et al. 2011, MNRAS 412, 2735) and other high-luminosity,
slow-ejecta-velocity (sometimes labelled as "super-Chandrasekhar-mass")
type-Ia supernovae soon after maximum light.  Accounting for a Galactic
extinction A(R) = 0.75 (Schlafly and Finkbeiner 2011, Ap.J. 737, 103) and a
distance modulus of 34.45, the inferred absolute magnitude is -19.3.  Note,
however, that narrow interstellar Na I D lines with similar equivalent width
are visible both at rest wavelength and at the redshift of the host galaxy,
suggesting significant additional internal extinction and, hence, an even
brighter absolute magnitude for 2013S.  The Asiago classification spectra
are posted at website URL http://graspa.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).


NOTE: These 'Central Bureau Electronic Telegrams' are sometimes
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                         (C) Copyright 2013 CBAT
2013 February 7                  (CBET 3406)              Daniel W. E. Green