Electronic Telegram No. 4217
Central Bureau for Astronomical Telegrams
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SUPERNOVA 2015bd IN NGC 3662 = PSN J11234588-0106212
     S. Nakano, Sumoto, Japan, reports the discovery by Koichi Itagaki
(Teppo-cho, Yamagata, Japan) of an apparent supernova (mag 15.9) on an
unfiltered CCD frame (limiting magnitude 19.0) taken on Dec. 7.843 UT using a
0.60-m f/5.7 reflector.  The new object is located at R.A. = 11h23m45s.88,
Decl. = -1d06'21".2 (equinox J2000.0; reference stars from UCAC4 catalogue),
which is 7".8 west and 2".8 south of the nucleus of the galaxy NGC 3662
(which has measured position end figures 46s.40, 18".4).  Itagaki posted his
discovery image at website http://k-itagaki.jp/images/n3662.jpg.  The variable
was designated PSN J11234588-0106212 when it was posted at the Central
Bureau's TOCP webpage and is here designated SN 2015bd based on the
spectroscopic confirmation reported below.  Additional unfiltered CCD
magnitudes for 2015bd:  2001 Mar. 15.578, [19.0 (Itagaki); 2015 Dec. 8.533,
15.5 (S. Kiyota, Kamagaya, Japan; remotely with an iTelescope 0.43-m f/4.5
CDK astrograph + FLI-PL6303E camera near Mayhill, NM, USA; image posted at URL
http://meineko.sakura.ne.jp/ccd/PSN_J11234588-0106212.jpg); 8.689, 15.9 (K.
Shima, Fujimi-machi, Nagano, Japan; 45-cm f/4.6 reflector + FLI ML-8300
camera; 60-s exposure; position end figures 45s.88, 21".6); 8.723, 15.3
(T. Noguchi, Katori, Chiba-ken, Japan; 0.23-m f/6.3 reflector; position end
figures 45s.90, 20".8; galaxy center position end figures 47s.04, 14".9; image
posted at website URL http://park8.wakwak.com/~ngc/images/PSNinNGC3662.jpg;
communicated by Nakano).

     K. Ayani, Bisei Astronomical Observatory (BAO), Ibara, Okayama, Japan,
obtained a low-resolution spectrogram (range 400-800 nm; resolution 0.7 nm
at H-alpha) of PSN J11234588-0106212 = SN 2015bd with the BAO 1.01-m telescope
on Dec. 8.9 UT.  The spectrum is that of a type-Ia supernova a few weeks past
maximum.  Cross-correlation with a library of supernova spectra using the
"SuperNova Identification" code (SNID; Blondin and Tonry 2007, Ap.J. 666,
1024) shows that 2015bd matches best with SN 1999gp (a peculiar 1991T-like
type-Ia event) at 21 days past maximum.  The spectrum is viewable via website
URL http://tinyurl.com/zwm93a7.

     T. Nakaoka, R. Itoh, K. S. Kawabata, K. Takaki, and M. Kawabata,
Hiroshima University; and M. Yamanaka, Konan University, obtained a
low-resolution optical spectrogram (range 450-900 nm) of PSN
J11234588-0106212 = SN 2015bd on Dec. 8.9 UT with the 1.5-m Kanata telescope
(+ HOWPol) at the Higashi-Hiroshima Observatory.  The spectrum shows
absorption lines of a Fe II multiplet, Si II 635.5-nm, and the Ca II near-
infrared triplet, suggesting that this is a type-Ia supernova.  The
absorption line of Si II 635.5-nm is blueshifted by about 8000 km/s.  A
comparison with a library of supernova spectra using GELATO (Harutyunyan et
al. 2008, A.Ap. 488, 383) reveals that the spectrum gives a good match to
normal type-Ia supernovae at a couple of weeks after maximum -- e.g., SN
2001V at 2-3 weeks after B-band maximum.


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

                         (C) Copyright 2015 CBAT
2015 December 10                 (CBET 4217)              Daniel W. E. Green