[IAUC] CBET 4219: 20151215 : SUPERNOVA 2015bf IN NGC 7653 = PSN J23244903+1516520

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                                                  Electronic Telegram No. 4219
Central Bureau for Astronomical Telegrams
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Prepared using the Tamkin Foundation Computer Network


SUPERNOVA 2015bf IN NGC 7653 = PSN J23244903+1516520
     S. Nakano, Sumoto, Japan, reports the discovery by Koichi Itagaki
(Teppo-cho, Yamagata, Japan) of an apparent supernova (mag 17.3) on an
unfiltered CCD frame (limiting magnitude 19.5) taken on Dec. 12.468 UT using
a 0.60-m f/5.7 reflector.  The new object is located at R.A. = 23h24m49s.03,
Decl. = +15d16'52".0 (equinox J2000.0; reference stars from UCAC4 catalogue),
which is 4".3 west and 20".1 north of the nucleus of the galaxy NGC 7653
(whose position end figures were measured to be 49s.33, 31".9).  Itagaki has
posted his discovery image at website URL http://k-itagaki.jp/7653.jpg.
The variable was designated PSN J23244903+1516520 when it was posted at the
Central Bureau's TOCP webpage and is here designated SN 2015bf based on the
spectroscopic confirmation reported below.  Additional CCD magnitudes
(unfiltered unless noted otherwise) for 2015bf:  2006 Aug. 3.602, [19.5
(Itagaki); 2015 Dec. 9.481, [19.0 (Itagaki); 12.496, 17.4 (K. Shima, Fujimi-
machi, Nagano, Japan; 45-cm f/4.6 reflector; position end figures 49s.02,
51".3); 12.510, 17.1 (T. Noguchi, Katori, Chiba-ken, Japan; 0.23-m Schmidt-
Cassegrain reflector; position end figures 49s.02, 51".5; galaxy center
position end figures 49s.33, 31".9; communicated by Nakano; image posted at
website URL http://park8.wakwak.com/~ngc/images/PSNinNGC7653.jpg); 12.727,
17.1 (G. Masi; remotely using a 43-cm telescope at Ceccano, Italy; position
end figures 49s.04, 51".7); 12.776, 17.0 (P. Corelli, Pagnacco, Italy; 45-cm
telescope; position end figures 49s.01, 51".7; image posted at website URL
https://www.flickr.com/photos/52195265@N06/23335714039/in/dateposted-public/);
12.875, R_c = 17.2 (G. Locatelli, Cuneo, Italy; 25-cm Schmidt-Cassegrain
f/10 reflector; fifteen stacked 120-s exposures; limiting mag 18.0).

     Jujia Zhang, Yunnan Astronomical Observatories (YNAO); and Xiaofeng Wang
and Kaicheng Zhang, Tsinghua University, report that an optical spectrum of
PSN J23244903+1516520 = SN 2015bf, obtained on Dec. 13.5 UT with the 2.4-m
telescope (+ YFOSC) at the Lijiang Observatory of the YNAO, shows it to be a
type-IIn supernova.  The spectrum is characterized by broad H, He II, and C
IV/N III emission lines with narrow peaks, superimposed on a very blue
continuum (T about 17000 K).  Cross-correlation with a library of supernova
spectra using the comparison tool "Gelato" (Harutyunyan et al. 2008, A.Ap.
488, 383) shows that 2015bf matches with SN 1998S at 3.5 days after the
explosion.


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

                         (C) Copyright 2015 CBAT
2015 December 15                 (CBET 4219)              Daniel W. E. Green