[IAUC] CBET 2985: 20120121 : SUPERNOVA 2012I = PSN J02582783+0611253

Vie Ene 20 19:07:14 ART 2012

                                                  Electronic Telegram No. 2985
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 2012I = PSN J02582783+0611253
     A. J. Drake, S. G. Djorgovski, M. J. Graham, A. Mahabal, and R. Williams,
California Institute of Technology; J. L. Prieto, Princeton University; M.
Catelan, Pontificia Universidad Catolica de Chile; E. C. Beshore and S. M.
Larson, Lunar and Planetary Laboratory, University of Arizona; and E.
Christensen, Gemini Observatory, report the discovery of an apparent supernova
in unfiltered Catalina Sky Survey (CSS) images:

 SN       2012 UT       R.A. (2000.0) Decl.      Mag.      Offset
 2012I    Jan. 18.17   2 58 27.83  + 6 11 25.3   16.3    1".6 E, 6".4 S

The variable was designated PSN J02582783+0611253 when it was posted at the
Central Bureau's TOCP webpage and is here designated SN 2012I based on the
spectroscopic confirmation reported below.  Additional CCD magnitudes for
2012I:  2011 Dec. 31.10 UT, [20.5 (CSS); 2012 Jan. 18.913, 16.4 (Paolo Corelli,
Pagnacco, Italy; 0.45-m f/4.5 telescope; position end figures 27s.83, 24".9;
limiting mag 17.8; unfiltered); 19.113, 16.4 (Joseph Brimacombe, Cairns,
Australia; remotely using a 51-cm RCOS telescope + STL11K camera + luminance
filter at New Mexico Skies Observatory near Mayhill, NM, U.S.A.; position end
figures 27s.80, 25".2; image posted at the following website URL:
http://www.flickr.com/photos/43846774@N02/6727514697/).

     M. R. Drout, D. Milisavljevic, E. Berger, N. Sanders, and A. M. Soderberg,
Harvard University, report on low-dispersion spectra (range 330-850 nm) taken
on Jan. 19 UT with the 6.5-m MMT (+ Blue Channel).  PSN J02582783+0611253 = SN
2012I is a type-Ia supernova near maximum light.  Comparison with a library
of supernova spectra using the "Supernova Identification" tool (SNID; Blondin
and Tonry 2007, Ap.J., 666, 1024) provides a good match with the normal type-Ia
supernova 1994D at four days before maximum.  Using the SNID-determined
redshift of z = 0.029, the velocity of the Si II 635.5-nm feature is estimated
to be approximately 11500 km/s.

     L. Magill and R. Kotak, Queen's University, Belfast, report that an
optical spectrum (range 330-900 nm) of PSN J02582783+0611253 = SN 2012I was
obtained at the Isaac Newton Telescope (+ Intermediate Dispersion Spectrograph)
on Jan. 19.92 UT.  Cross-correlation with a library of supernova spectra using
the Supernova Identification tool (SNID; Blondin and Tonry, 2007, Ap.J. 666,
1024) resulted in a best match the normal type-Ia supernova 2002er (Kotak et
al. 2005, A.Ap. 436, 1021) at an epoch of -4 days, at a redshift of 0.03.

     M. Dennefeld, Institut d'Astrophysique de Paris; J. Whitbourne, University
of Durham; and S. Benetti, Istituto Nazionale di Astrofisica, report that a
spectrum (range 370-730 nm; resolution 0.66 nm) of PSN J02582783+0611253 = SN
2012I was obtained on Jan. 19.76 UT with the Haute-Provence 1.93-m telescope
(+ Carelec).  Using a library of supernova spectra via GELATO (Harutyunyan et
al. 2008, A.Ap. 488, 383; available at URL https://gelato.tng.iac.es/login.cgi),
they found a best fit with normal type-Ia supernovae a few days after maximum.
Allowing for a galaxy redshift of z = 0.022099 (Stein 1996, A.Ap. Suppl. 116,
203; via NED), the expansion velocity measured from the deep Si II 635.5-nm
absorption is 9400 km/s.

     Nearly 24 hours after this object was posted at the TOCP as noted above,
W. Zheng, University of Michigan; J. Vinko, University of Szeged; R. Quimby,
IPMU, University of Tokyo; N. Whallon, A. Romadan, C. Wagner, and C. Akerlof,
University of Michigan; F. Yuan, Australian National University; J. C. Wheeler
and E. Chatzopoulos, University of Texas; and G. H. Marion, Harvard-Smithsonian
Center for Astrophysics, on behalf of the ROTSE collaboration, reported the
independent discovery of 2012I at mag about 16.6 in unfiltered images taken on
Jan. 12.16 UT with the 0.45-m ROTSE-IIIb telescope at McDonald Observatory.
They measure 2012I to be located at R.A. = 2h58m27s.8, Decl. = +6o11'25".5
(equinox 2000.0; uncertainty about 1"), adding that there is no apparent host
galaxy at this position in a Sloan Digital Sky Survey (SDSS) image; the
nearest object in the SDSS image is a faint galaxy with magnitude r' = 19.59
lying 1".1 east and 6".2 north of 2012I.  Additional approximate ROTSE
magnitudes for 2012I:  Jan. 14.07, 16.4; 15.10, 16.2; 18.08, 16.2.  They
provide a finding chart for 2012I at the following website URL:
http://www.rotse.net/rsvp/j025827.8+061126/ROTSE3_J025827.8+061126.jpg.
     A spectrum, obtained on Jan. 17.15 UT with the 9.2-m Hobby-Eberly
Telescope (+ Marcario Low-Resolution Spectrograph) by S. Odewahn, shows that
2012I is a type-Ia supernova near maximum light.  The spectrum contains the
Si II 635.5-nm line and several other characteristic type-Ia-supernova
features.  According to SNID (Blondin and Tonry 2007, Ap.J. 666, 1024), the
spectrum most resembles to that of SN 1996X (at 1.9 days after maximum) and
that of SN 2002bo (at 4.4 days before maximum).  The median redshift estimate
is z = 0.029.  Adopting this redshift, the velocity from the absorption
minimum of the Si II 635.5-nm feature is 11000 km/s.  The R(Si II) ratio is
about 0.35, suggesting a type-Ia supernova in the "Low Velocity Gradient"
subclass (Benetti et al. 2005, Ap.J. 623, 1011; Altavilla et al. 2009, Ap.J.
695, 135).

NOTE: These 'Central Bureau Electronic Telegrams' are sometimes
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                         (C) Copyright 2012 CBAT
2012 January 21                  (CBET 2985)              Daniel W. E. Green