[IAUC] CBET 3484: 20130421 : SUPERNOVA 2013bl IN UGC 4578 = PSN J08461506+4134400

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                                                  Electronic Telegram No. 3484
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 2013bl IN UGC 4578 = PSN J08461506+4134400
     D. Rich, J. Rosebush, and C. Sawyer report their discovery of an apparent
supernova (mag about 18.0) on unfiltered CCD frames (limiting mag 19.2) taken
with a 0.41-m reflector on Apr. 7.077 UT in Hampden, ME, U.S.A., in the course
of the Eagle Hill Supernova Search Project.  The new object is located at R.A.
= 8h46m15s.06, Decl. = +41o34'40".0 (equinox 2000.0), which is about 10".8
east and 7".2 south of the center of UGC 4578.  Nothing is visible at this
location on Palomar Digital Sky Survey images from 1989 Mar. 9 (limiting red
mag about 20.3) and 1994 Jan. 11 (limiting blue mag about 21.0).  The variable
was designated PSN J08461506+4134400 when it was posted at the Central
Bureau's TOCP webpage and is here designated SN 2013bl based on the
spectroscopic confirmation reported below.  Additional CCD magnitudes for
2013bl:  2013 Mar. 25.130, [19.0 (Rich); Apr. 8.043, 17.8 (P. Burke,
Pittsfield, ME, U.S.A.; 0.35-m reflector; limiting mag 18.6; via Rich); 8.318,
19.4 (Joseph Brimacombe, Cairns, Australia; remotely using a 51-cm RCOS
telescope + STL11K camera + luminance filter at the New Mexico Skies
observatory near Mayhill, NM, U.S.A.; position end figures 15s.02, 41".1;
image posted at URL http://www.flickr.com/photos/43846774@N02/8632917313/);
14.009, 18.4 (Federica Luppi and Luca Buzzi, Varese, Italy; 0.38-m f/6.8
reflector; position end figures 14s.99, 40".7; reference stars from CMC-14
catalogue; image posted at http://www.astrogeo.va.it/pub/TOCP/PSN_U4578.jpg).

     L. Tomasella, S. Benetti, A. Pastorello, E. Cappellaro, M. Turatto, and
P. Ochner, Osservatorio Astronomico di Padova, Istituto Nazionale di
Astrofisica, report that optical spectroscopy (range 340-820 nm; resolution
1.3 nm), obtained on Apr. 17.82 UT with the Asiago 1.82-m Copernico Telescope
(+ AFOSC), shows that PSN J08461506+4134400 = SN 2013bl is a stipped-envelope
supernova, in agreement with Pecontal et al. 2013 (as posted at website URL
http://www.astronomerstelegram.org/?read=4971).  However, adopting a redshift
of z about 0.030 for the host galaxy, UGC 4578 (Sloan Digital Sky Survey Data
Release 2, 2004), the best match has been found with several type-IIb
supernovae a few weeks after maximum light.  Together with He I and Fe II
lines, H_alpha is clearly detected.  The expansion velocity of the ejected
material, as deduced from the position of the strong He-I 587.6-nm absorption,
is about 8000 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).


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

                         (C) Copyright 2013 CBAT
2013 April 21                    (CBET 3484)              Daniel W. E. Green