[IAUC] CBET 3551: 20130609 : SUPERNOVA 2013dc IN NGC 6240 = PSN J16525897+0224255

Dom Jun 9 10:28:02 ART 2013

                                                  Electronic Telegram No. 3551
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 2013dc IN NGC 6240 = PSN J16525897+0224255
     Adam Block, Steward Observatory, reports the discovery of an apparent
supernova (mag 18.7) on 900-s CCD exposures taken on Apr. 11 and 12 with a
0.8-m f/7 telescope (+ SBIG STX 16803 camera + clear filter with infrared
block) at the Mount Lemmon SkyCenter.  The new object is located at R.A. =
16h52m58s.97, Decl. = +2d24'25".2 (equinox 2000.0), which is 25" north of the
nucleus of NGC 6240 along the plane of the galaxy itself.  He notes the
presence of an H II/star-forming region (but no star, as is now visible) in
this position on Hubble Space Telescope images.  The variable was designated
PSN J16525897+0224255 when it was posted at the Central Bureau's TOCP webpage
and is here designated SN 2013dc based on the spectroscopic confirmation
reported below.  The type-IIn supernova 2000bg also appeared in NGC 6240 (cf.
IAUC 7392).  Additional clear-filter magnitudes for 2013dc from Block: Apr. 13,
18.9; 14, 18.9; 19, 19.0; 20, 19.0; 21, 19.0; May 26, 20.3.  Green-filter
(broadband, similar to V) magnitudes for the variable from Block:  Apr. 18,
18.8; 19, 18.9; 20, 18.9; 21, 18.9.  Additional CCD magnitues for 2013dc:
May 19.928, 18.9 (Gianluca Masi and Francesca Nocentini, remotely using the
43-cm robotic telescope at Ceccano, Italy; co-added images; position end
figures: 59s.01, 25".8; image scale 1".2/pixel; image posted at website URL
http://www.virtualtelescope.eu/2013/05/21/psn-j165258970224255-in-ngc-6240/);
20.231, 18.9 (Joseph Brimacombe, Cairns, Australia; remotely with a 51-cm
telescope + luminance filter at the New Mexico Skies observatory near Mayhill,
NM, U.S.A.; position end figures 58s.94, 24".5; image posted at website URL
http://www.flickr.com/photos/43846774@N02/8764298096/); 20.392, [20.2 (L.
Elenin, Lyubertsy, Russia; and I. Molotov, Moscow; three 150-s images remotely
taken with a 0.45-m f/2.8 telescope at the ISON-NM Observatory  near Mayhill;
scale 2"/pixel); 21.239, 18.4 (Brimacombe; infrared filter with bandpass >
700 nm; position end figures 58s.91, 24".6; image posted at website URL
http://www.flickr.com/photos/43846774@N02/8785083663/).

     L. Tomasella, S. Benetti, A. Pastorello, E. Cappellaro, P. Ochner, and M.
Turatto, Osservatorio Astronomico di Padova, Istituto Nazionale di
Astrofisica, report that an optical spectrogram of PSN J16525897+0224255 = SN
2013dc (range 340-820 nm; resolution 1.3 nm), obtained on June 7.05 UT with
the Asiago 1.82-m Copernico Telescope (+ AFOSC), shows that this is a type-II
supernova at redshift z about 0.0245 (Downes et al. 1993, Ap.J. 414, L13; via
NED).  A good match is found with normal type-II-P supernovae about two
months after explosion.  The expansion velocity, deduced from the H-alpha
absorption, is about 6900 km/s.  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).

     S. B. Cenko, Goddard Space Flight Center, NASA: W. Zheng, A. V.
Filippenko, O. D. Fox, and K. I. Clubb, University of California, Berkeley;
and S. D. Van Dyk, IPAC, California Institute of Technology, report that
inspection of a CCD spectrogram (range 340-1000 nm), obtained on June 7.3 UT
with the Shane 3-m reflector (+ Kast spectrograph) at Lick Observatory, shows
that PSN J16525897+0224255 = SN 2013dc is a type-II supernova.  Cross-
correlation with a library of supernova spectra using the "SuperNova
Identification" code (SNID; Blondin and Tonry 2007, Ap.J. 666, 1024) results
in best matches with a number of type-IIP supernovae when at least several
weeks past maximum light.


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                         (C) Copyright 2013 CBAT
2013 June 9                      (CBET 3551)              Daniel W. E. Green