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SN 2011gc in pgc1651633 - 27 giugno 2011

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SN 2011gc (A.R. 18 12 19.00, Dec. +21 31 15.0) scoperta il 27 giugno 2011 nella galassia PGC 1651633 (offset 5E 12N), magnitudine 17.3, tipo II plateau.

SN scoperta da F. Ciabattari, S. Donati e G. Fornaciari con il telescopio Newton da 50cm dell'Osservatorio di Monte Agliale (Lucca).

PGC 1651633 è una galassia irregolare nella costellazione dell'Ercole.

                                                  Electronic Telegram No. 2835
Central Bureau for Astronomical Telegrams
CBAT Director: Daniel W. E. Green; Hoffman Lab 209; Harvard University;
20 Oxford St.; Cambridge, MA 02138; U.S.A.
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Prepared using the Tamkin Foundation Computer Network

SUPERNOVA 2011gc = PSN J18121900+2131150 = PSN J18121913+2131136
F. Ciabattari, S. Donati, and G. Fornaciari, Borgo a Mozzano, Italy,
report the discovery of an apparent supernova (mag 17.8) on unfiltered CCD
images (limiting mag 19.2) obtained on June 27.87 UT with a 0.5-m Newtonian
telescope in the course of the Italian Supernovae Search Project. The new
object is located at R.A. = 18h12m19s.24, Decl. = +21d31'15".2 (equinox
2000.0; astrometry with respect to UCAC-2 stars), which is 5" east and 12"
north of the center of the presumed host galaxy. Nothing is visible at this
position on digitized plates of the Palomar Sky Survey from 1993 Aug. 13
(F plate; limiting magnitude 20.3) and 1995 Aug. 23 (J plate; limiting
magnitude 20.3) or on their own images from May 2011 (limiting mag 18.8).
The variable was designated PSN J18121900+2131150 when it was posted at the
Central Bureau's TOCP webpage and is here designated SN 2011gc based on the
spectroscopic report below. (Provisional designation PSN J18121913+2131136
was also assigned to this object when an independent discovery by Koichi
Itagaki was posted to the TOCP after the posting by Ciabattari et al.)
Additional CCD magnitudes for 2011gc (unfiltered unless otherwise noted):
2006 Aug. 2.572, [21.0 (K. Itagaki, Teppo-cho, Yamagata, Japan; communicated
by S. Nakano, Sumoto); 2011 June 28.81, 17.6 (Ciabattari et al.; limiting
magnitude 19.5); 29.268, 17.3 (Joseph Brimacombe, Cairns, Australia; position
end figures 19s.18, 14".7); July 2.044, 17.4 (Xavier Bros, Ager, Catalonia,
Spain, 35-cm f/4.6 telescope + ST8-XME camera; position end figures 19s.20,
14".0; UCAC-2 reference stars); 11.993, R = 17.7 (Federica Luppi, Varese,
Italy; 0.36-m f/7.9 reflector + Bessell R filter; position end figures 19s.17,
14".3; reference stars from CMC-14 catalogue); 20.889, 17.7 (S. Leonini,
Siena, Italy, 0.53-m f/8.7 Ritchey-Chretien telescope + Apogee Alta U47
camera); Aug. 4.577, 17.9 (Itagaki; 0.60-m f/5.7 reflector + BITRAN BT-21
camera; position end figures 19s.13, 13".9; communicated by Nakano); 4.871,
17.6 (S. Foglia and G. Galli, Pogliano Milanese, Italy; 0.28-m f/6.8 Schmidt-
Cassegrain reflector + ST8XME camera; position end figures 19s.15, 14".3;
UCAC-2 reference stars); 6.620, 17.7 (Itagaki; limiting magnitude 20.0;
position end figures 19s.13, 13".6; offset 3".6 east, 9".9 north; independent
discovery; communicated by Nakano); 8.19, 17.8 (R. A. Koff, Bennett, CO, USA;
Meade 0.25-m f/10 Schmidt-Cassegrain reflector + Apogee AP-47p CCD camera;
image scale 1"/pixel; position end figures 19s.14, 13".7; UCAC3 reference
stars; brightness uncertain by 0.5 mag due to background glow from presumed
host galaxy); 10.845, 17.6 (V. Gerke and S. Korotkiy, Ka-Dar Observatory, TAU
Station, Nizhny Arkhyz, Russia; 40-cm telescope + STL-11000M camera; position
end figures 19s.16, 14".1).
Brimacombe's June 29 image is posted at the following website URL:
http://www.flickr.com/photos/43846774@N02/5885982777/. Luppi's image from
July 11 is posted at http://www.astrogeo.va.it/pub/TOCP/PSN_U1651633.jpg.
Itagaki's image from Aug. 6 is at URL http://www.k-itagaki.jp/images/6577.jpg.

S. Valenti, S. Benetti, L. Tomasella, and P. Ochner, Osservatorio
Astronomico di Padova, Istituto Nazionale di Astrofisica; and A. Pastorello,
Dipartimento di Astronomia, Universita di Padova, on behalf of a larger
collaboration, report that a spectrogram (range 360-810 nm; resolution 2.2 nm)
of PSN J18121900+2131150 = SN 2011gc, obtained on Sept. 25.86 UT with the
Ekar-Copernico 1.82-m telescope (+ AFOSC), shows it to be a type-IIP supernova.
Cross-correlation with a library of supernova spectra using the "Supernova
Identification" code (SNID; Blondin and Tonry 2007, Ap.J. 666, 1024) suggests
a normal type-II-plateau supernova about 2-3 months after explosion (the
deduced redshift is 0.016). The spectrum shows intense P-Cyg lines typical of
the H recombination phase. Together with prominent H_alpha, lines of Fe II,
Ti II, Sc II, Ba II, and Na I D are clearly visible. The expansion velocity
derived from the H_alpha minimum is about 5400 km/s.

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

(C) Copyright 2011 CBAT
2011 September 29 (CBET 2835) Daniel W. E. Green