[IAUC] CBET 3092: 20120426 : SUPERNOVA 2012bv IN NGC 6796 = PSN J19213020+6108101

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                                                  Electronic Telegram No. 3092
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 2012bv IN NGC 6796 = PSN J19213020+6108101
     S. Nakano, Sumoto, Japan, reports the discovery by Masaki Tsuboi
(Kuchita-minami, Asakita-ku, Hiroshima, Japan) of an apparent supernova (mag
15.7) on a 30-s unfiltered CCD frame (limiting magnitude 18.1) taken on Apr.
8.751 UT using a 0.25-m f/4.7 reflector (+ ST-2000XM camera), which was then
confirmed on an earlier frame taken one day before discovery (limiting mag
18.3).  Tsuboi's position for the new object (averaged from the two images)
is R.A. = 19h21m30s.34 +/- 0s.14, Decl. = +61d08'10".8 +/- 0".7 (equinox
2000.0), which is 4".3 west and 32".2 south of the center of NGC 6796.
Tsuboi adds that nothing is visible at this position on the Digitized Sky
Survey (limiting red mag 19 or fainter).  The variable was designated PSN
J19213020+6108101 when it was posted at the Central Bureau's TOCP webpage
and is here designated SN 2012bv based on the spectroscopic confirmation
reported below.  Additional CCD magnitudes reported for 2012bv (unfiltered
unless noted otherwise):  1991 Sept. 1, [18.0 (Digitized Sky Survey, red
plate; via T. Yusa, Osaki, Japan); 2012 Mar. 28.781, [19.0 (Tsuboi); Apr.
1.817, [18.6 (Tsuboi); 7.722, 16.2 (Tsuboi); 9.436, 15.8 (R. A. Koff, Bennett,
CO, USA; Meade 0.25-m f/10 reflector + Apogee AP-47p camera; limiting mag
17.5; position end figures 30s.31, 11".2; UCAC3 reference stars; 9.400, 15.1
(L. Elenin, Lyubertsy, Russia; and I. Molotov, Moscow, Russia; images remotely
taken at the ISON-NM Observatory near Mayhill, NM, USA, with a 0.45-m f/2.8
telescope; position end figures 30s.40 +/- 0".12, 12".1 +/- 0".13; NOMAD
reference stars; limiting mag about 19.2; image posted at website URL
http://spaceobs.org/images/TOCP/PSNJ19213020+6108101-20120409.png); 9.579, 15.0
(T. Noguchi, Katori, Chiba-ken, Japan; 0.23-m f/6.3 reflector + BITRAN BT-11E
camera; limiting mag 18.0; position end figures 30s.36, 12".0; offset 4".1 west
and 30".6 south; communicated by Nakano); 9.675, 15.8 (K. Itagaki, Yamagata,
Japan; 0.60-m f/5.7 reflector; position end figures 30s.35, 11".4; image posted
at website URL http://www.k-itagaki.jp/images/6796.jpg); 9.709, 15.6 (K.
Kadota, Saitama-ken, Japan; 0.25-m f/5.0 reflector; position end figures
30s.38, 11".9); 10.429, 16.1 (Joseph Brimacombe, Cairns, Australia; luminance
filter; position end figures 30s.28, 10".8); 12.366, 16.1 (T. Yusa, Osaki,
Japan; remotely using the "iTelescope T5" 0.25-m f/3.4 astrograph + SBIG
ST-10XME camera near Mayhill; position end figures 30s.35, 11.3; UCAC-3
reference stars; limiting magnitude 19.5).  Yusa's image is posted at website
URL http://space.geocities.jp/yusastar77/supernova/PSNinNGC6796_120412.htm.

     V. Stanishev, Centro Multidisciplinar de Astrofisica, Instituto Superior
Tecnico, Lisbon; M. Stritzinger, Aarhus University; and R. Amanullah and A.
Goobar, Stockholm University, report that a spectrogram of PSN
J19213020+6108101 = SN 2012bv, obtained on Apr. 10.18 UT by D. Oszkiewicz and
S. Geier with the Nordic Optical Telescope (+ ALFOSC; range 330-910 nm), shows
it to be a type-II supernova soon after explosion.  The spectrum consists of a
blue continuum superimposed with weak P-Cyg hydrogen Balmer lines.  Adopting
for the host galaxy, NGC 6796, a recession velocity of 2189 km/s (Theureau et
al. 1998, A.Ap. Suppl. 130, 333), the absorption component of H_alpha is
found to be blue-shifted by roughly 9100 km/s.

     K. Ayani, Bisei Astronomical Observatory (BAO), Okayama, Japan; and H.
Yamaoka, Kyushu University, report that low-resolution spectroscopy (range
400-800 nm; resolution 0.5 nm) of PSN J19213020+6108101 = SN 2012bv was
carried out on Apr. 11.8 UT with the 1-m BAO telescope; despite the poor-S/N
ratio of the spectrum, preliminary inspection reveals P-Cyg profiles of
H-alpha and H-beta, whose absorption bottoms are blueshifted by 9000 and 9200
km/s respectively, assuming a heliocentric velocity for NGC 6796 of 2189 km/s
(Theureau et al. 1998, A.Ap. Suppl. 130, 333).  On Apr. 23.7, Ayani and S.
Maeno obtained spectroscopy with the same instrumentation, revealing a
prominent, broad (FWHM about 9000 km/s) H-alpha emission line.  The absorption
bottom of the P-Cyg profile of H-beta is blueshifted by 7500 km/s with respect
to the systemic velocity of NGC 6796.  Absorption of Fe II 516.9-nm can be
seen.  These feature confirm that 2012bv is a type-II supernova.  The spectrum
is posted at http://www.bao.go.jp/astro/2012/sn/PSN_J19213020+6108101_Apr23.png.

     L. Tomasella, S. Benetti, E. Cappellaro, P. Ochner, A. Pastorello, M.
Turatto, and S. Valenti, Osservatorio Astronomico di Padova, Istituto
Nazionale di Astrofisica, report that a spectrogram of PSN J19213020+6108101
= 2012bv, obtained on Apr. 25.11 UT with the Asiago 1.82-m Copernico Telescope
(+ AFOSC; range 340-820 nm; resolution 2.4 nm), indicates that this is a
type-II supernova.  Cross-correlation with a library of supernova spectra via
the GELATO code (Harutyuyan et al. 2008, A.Ap. 488, 383), shows that, assuming
a redshift of z = 0.0073 for the host galaxy (average of different estimates
listed in the NASA/IPAC Extragalactic Database), 2012bv is similar to SN
2007od at ten days after explosion (Inserra et al. 2011, MNRAS 417, 261).


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                         (C) Copyright 2012 CBAT
2012 April 26                    (CBET 3092)              Daniel W. E. Green