[IAUC] CBET 4173: 20151115 : SUPERNOVA 2015ab IN NGC 938 = PSN J02283286+2017077

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                                                  Electronic Telegram No. 4173
Central Bureau for Astronomical Telegrams
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Prepared using the Tamkin Foundation Computer Network


SUPERNOVA 2015ab IN NGC 938 = PSN J02283286+2017077
     K. Itagaki, Teppo-cho, Yamagata, Japan reports his discovery of an
apparent supernova (mag 17.3) in NGC 938 on an unfiltered CCD frame (limiting
mag 19.0) taken on July 10.744 UT using a 0.60-m f/5.7 reflector.  The new
object is located at R.A. = 2h28m32s.86, Decl. = +20d17'07".7 (equinox 2000.0;
reference stars from UCAC4 catalogue), which is 9".3 west and 6".3 north of
the nucleus of NGC 938.  Itagaki has posted his discovery image at website
URL http://k-itagaki.jp/images/938.jpg.  The variable was designated PSN
J02283286+2017077 when it was posted at the Central Bureau's TOCP webpage
and is here designated SN 2015ab based on the spectroscopic confirmation
reported below.  Additional CCD magnitudes for 2015ab:  July 12.143, 16.9
(T. Yusa, Osaki, Japan; 0.32-m f/8.0 astrograph + SBIG STXL-6303E camera
located at the at AstroCamp Observatory near Nerpio, Spain; three stacked
120-s frames; limiting mag 19.0; position end figures 32s.93, 07".8;
reference stars from UCAC-4 catalogue; image posted at website URL
http://space.geocities.jp/yusastar77/supernova/PSNinN938_150712.htm); 12.761,
16.7 (Itagaki; position end figures 32s.84, 08".3; communicated by S. Nakano,
Sumoto, Japan); 13.039, 16.2 (G. Masi; remotely using a 43-cm telescope at
Ceccano, Italy; position end figures 32s.85, 08".0).

     K. Ayani, Bisei Astronomical Observatory (BAO), Ibara, Okayama, Japan,
obtained a low-resolution spectrogram (range 400-675 nm; resolution 0.6 nm at
H-alpha) of PSN J02283286+2017077 = SN 2015ab with the BAO 1.01-m telescope
on July 26.8 UT.  The spectrum is that of a normal type-Ia supernova around
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 this possible supernova matches best with SN 1995E at 3.9
days past maximum.  Assuming a heliocentric velocity for NGC 938 of 4118
km/s (Caldwell et al. 2003, A.J. 125, 2891; via NED), the blueshift of the Si
II 635.5-nm absorption is about 10500 km/s.  The spectrum is viewable via
website URL http://tinyurl.com/o5mske8.


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                         (C) Copyright 2015 CBAT
2015 November 15                 (CBET 4173)              Daniel W. E. Green