[IAUC] CBET 3199: 20120810 : SUPERNOVA 2012ea IN NGC 6430 = PSN J17451040+1808268

Vie Ago 10 05:13:51 ART 2012

                                                  Electronic Telegram No. 3199
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 2012ea IN NGC 6430 = PSN J17451040+1808268
     Further to CBET 3121, S. B. Cenko, W. Li, and A. V. Filippenko report the
LOSS discovery of an apparent supernova on unfiltered KAIT images:

 SN       2012 UT       R.A. (2000.0) Decl.      Mag.      Offset
 2012ea   Aug. 8.29   17 45 10.40  +18 08 26.8   16.8    55".3 W, 7".0 N

The variable was designated PSN J17451040+1808268 when it was posted at the
Central Bureau's TOCP webpage and is here designated SN 2012ea based on the
spectroscopic confirmation reported below.  Additional CCD magnitudes for
2012ea:  May 9.77, 29.73, and June 21.64 UT, [18.2 (S. Shurpakov, D.
Denisenko, V. Yurkov, and E. Sinyakov; 0.40-m f/2.5 MASTER-Amur robotic
reflector + 16-megapixel camera); Aug. 6.27, [18.2 (KAIT); 8.607, 17.1
(Shurpakov et al.; position end figures 10s.41, 26".9; image posted at URL
http://master.sai.msu.ru/static/OT/PSNJ17451040+1808268-MASTER-Amur.jpg);
8.853, R_c = 17.3 (Massimiliano Martignoni, Magnago, Italy; 25-cm Schmidt-
Cassegrain reflector; position end figures 10s.42, 26".9); 9.163, 16.4
(L. Elenin, Lyubertsy, Russia, and I. Molotov, Moscow; remotely taken at
the ISON-NM Observatory near Mayhill, NM, USA, with a 0.45-m f/2.8
telescope; limiting mag about 20.1; position end figures 10s.40 +/- 0".11,
26".7 +/- 0".13; NOMAD reference stars; image posted at website URL
http://spaceobs.org/images/TOCP/PSNJ17451040+1808268-20120809.png); 9.261,
17.1 (Joseph Brimacombe, Cairns, Australia; luminance filter presumed;
position end figures 10s.45, 26".4; image posted at website URL
http://www.flickr.com/photos/43846774@N02/7751296588/).

     L. Tomasella, P. Ochner, S. Valenti, A. Pastorello, S. Benetti, E.
Cappellaro, and M. Turatto, Osservatorio Astronomico di Padova, Istituto
Nazionale di Astrofisica, report that a spectrogram of PSN J17451040+1808268
= 2012ea, obtained on Aug. 8.92 UT with the Asiago 1.82-m Copernico Telescope
(+ AFOSC; range 340-820 nm; resolution 2.4 nm), suggests that this is a
1991bg-like type-Ia supernova.  Adopting for the host galaxy (NGC 6430) a
redshift z = 0.010210 (Bottinelli et al. 1993, A.Ap. Suppl. 102, 57; via NED),
a comparison with a library of supernovae spectra via GELATO (Harutyuyan et
al. 2008, A.Ap. 488, 383) shows that 2012ea is similar to SN 2005bl
(Taubenberger et al. 2008, MNRAS 385, 75) a few days before maximum.  Adopting
the discovery magnitude of 17.3, a Virgo-corrected distance modulus of mag
33.23 and a Milky Way absorption of 0.14 mag, the supernova would have an
absolute magnitude of about -16.1, making it one of the faintest 1991bg-like
supernovae known.

     M. L. Graham, Las Cumbres Observatory Global Telescope Network; and J. M.
Silverman and S. B. Cenko, University of California, Berkeley, report that
inspection of a CCD spectrum (range 350-1000 nm), obtained on Aug. 9.28 UT
with the Shane 3-m reflector (+ Kast spectrograph) at Lick Observatory, shows
that PSN J17451040+1808268 = SN 2012ea is a 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) indicates
that 2012ea is a 1991bg-like supernova before maximum brightness.  After
removal of the host-galaxy recession velocity of 3061 km/s (Theureau et al.
1998, A.Ap. 130, 333; via NED), the absorption minimum of the Si II 635.5-nm
line is found to be blueshifted by about 16000 km/s.

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

                         (C) Copyright 2012 CBAT
2012 August 10                   (CBET 3199)              Daniel W. E. Green