[IAUC] CBET 3349: 20121222 : SUPERNOVA 2012ht IN NGC 3447 = PSN J10532275+1646349

Vie Dic 21 22:47:20 ART 2012

                                                  Electronic Telegram No. 3349
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 2012ht IN NGC 3447 = PSN J10532275+1646349
     Koichi Nishiyama, Kurume, Japan; and Fujio Kabashima, Miyaki, Japan,
report the discovery of an apparent supernova (mag 18.6) on seven unfilterd
40-s CCD frames (limiting mag 20.2) taken around Dec. 18.772 UT using a 0.4-m
f/9.8 reflector.  The new object is located at R.A. = 10h53m22s.75, Decl. =
+16d46'34.9 (equinox 2000.0), which is 19" west and 16" north of the center of
the galaxy NGC 3447.  Nothing is visible at this position on Digitized Sky
Survey red and infrared plates.  The variable was designated PSN
J10532275+1646349 when it was posted at the Central Bureau's TOCP webpage and
is here designated SN 2012ht based on the spectroscopic confirmation reported
below.  Additional magnitudes for 2012ht (obtained via unfiltered CCD unless
otherwise noted):  1986 Dec. 31, [19.2 (Digitized Sky Survey, red plate; via
T. Yusa, Osaki, Japan); 2010 Dec. 4.809, [19.9 (Nishiyama and Kabashima);
2011 Jan. 10.800, [19.7 (Nishiyama and Kabashima); 2012 Dec. 16.736, [18.5 (K.
Itagaki, Yamagata, Japan); 19.600, 16.8 (Toshihide Noguchi, Katori, Chiba-ken,
Japan, 0.23-m f/6.3 reflector; limiting mag 18.5; position end figures 22s.67,
35".3; galaxy center has position end figures measured as 24s.06, 19".7; UCAC3
reference stars; communicated by S. Nakano, Sumoto, Japan; image posted at
website URL http://park8.wakwak.com/~ngc/images/PSNinNGC3447.jpg); 19.660,
16.9 (Nishiyama and Kabashima; position end figures 22s.74, 34".7); 20.317,
16.3 (Yusa; remotely using a iTelescope 0.25-m f/3.4 astrograph + SBIG
ST-10XME camera at the RAS Observatory near Mayhill, NM, U.S.A.; position end
figures 22s.68, 34".8; USNO-B1.0 catalogue reference stars; limiting mag 18.5);
20.677, 16.6 (Joseph Brimacombe, Cairns, Australia; 41-cm RCOS telescope +
STL6K camera + infrared filter; bandpass > 700 nm; image posted at website URL
123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789
http://www.flickr.com/photos/43846774@N02/8295446108/); 20.724, 16.1
(Nishiyama and Kabashima; position end figures 22s.69, 34".4; limiting mag
20.1); 21.492, 15.9 (Yusa; limiting mag 18.0; image posted at website URL
http://space.geocities.jp/yusastar77/supernova/PSNinN3447_121220.htm#21UT).
Yusa's earlier Dec. 20 image of 2012ht is posted at the following website URL:
http://space.geocities.jp/yusastar77/supernova/PSNinN3447_121220.htm.

     D. Milisavljevic, Harvard-Smithsonian Center for Astrophysics; and E. O.
Martin, MMT Observatory, report that low-dispersion spectra (range 330-850 nm),
obtained ON Dec. 20.4 UT with the 6.5-m MMT reflector (+ Blue Channel), show
PSN J10532275+1646349 = SN 2012ht to be a young 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) shows a
reasonable match to SN 2008ar about a week before maximum light.  After
removal of the host-galaxy (NGC 3447) redshift of z = 0.003559 (via NED;
Guthrie and Napier 1995, A.Ap. 310, 353), the absorption minimum of the Si II
635.5-nm line is found to be blueshifted by approximately -14500 km/s.
A C II 658.0-nm feature is clearly detected.

     M. Yamanaka, Kyoto University; K. Takaki, R. Itoh, I. Ueno, Y. Moritani,
H. Akitaya, and K. S. Kawabata, Hiroshima University; and A. Arai,
Nishi-harima Astronomical Observatory, obtained a low-resolution optical
spectrum (range 480-900 nm) of PSN J10532275+1646349 = SN 2012ht on Dec. 20.6
UT with the 1.5-m Kanata telescope (+ HOWPol) at Higashi-Hiroshima Observatory.
The spectrum exhibits prominent absorption lines at 565, 610, and 800 nm,
identified as Si II 597.2- and 635.5-nm and the Ca II infrared triplet,
respectively.  A comparison with a library of supernova spectra using GELATO
(Harutyunyan et al. 2008, A.Ap. 488, 383) suggests that the spectrum of
2012ht is consistent with some type-Ia supernovae around maximum or about one
week before.  The relatively strong absorption feature of Si II 597.2-nm
might be a hint that this supernova belongs to a subluminous class of type Ia.


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

                         (C) Copyright 2012 CBAT
2012 December 22                 (CBET 3349)              Daniel W. E. Green