Electronic Telegram No. 4178
Central Bureau for Astronomical Telegrams
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SUPERNOVA 2015ae IN NGC 7753 = PSN J23470615+2929074
     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 mag 19.5) taken on Aug. 6.680 UT using a
0.60-m f/5.7 reflector.  The new object is located at R.A. = 23h47m06s.15,
Decl. = +29d29'07".4 (equinox 2000.0; reference stars from UCAC4 catalogue),
which is 17".5 east and 6".9 north of the nucleus of NGC 7753.  Itagaki posted
his discovery image at website URL http://k-itagaki.jp/images/7753.jpg.  The
variable was designated PSN J23470615+2929074 when it was posted at the
Central Bureau's TOCP webpage and is here designated SN 2015ae based on the
spectroscopic confirmation reported below.  SNe 2006A (cf. CBET 354) and
2013Q (CBET 3401) also appeared in NGC 7753.  Additional CCD magnitudes for
2015ae:  2006 Aug. 30.674, [19 (Itagaki; communicated by Nakano); 2015 Aug.
4.689, 17.7 (Itagaki; pre-discovery image; limiting mag 19.0; position end
figures 06s.13, 06".9; communicated by Nakano); 6.097, 17.5 (F. Ciabattari
and E. Mazzoni; pre-discovery image taken with a 0.5-m Newtonian telescope at
Borgo a Mozzano, Italy, in the course of the Italian Supernovae Search
Project; limiting magnitude 18.8; position end figures 06s.12, 07".3; image
posted at website URL https://www.flickr.com/photos/snimages/20392304542/);
6.995, V = 17.5 (M. Martignoni, Magnago, Italy; 25-cm f/10 Schmidt-Cassegrain
reflector; position end figures 06s.08, 06".6); 8.428, V = 16.91, I_c = 16.52
(S. Kiyota, Kamagaya, Japan; remotely with an iTelescope 0.61-m f/6.5 CDK
astrograph + FLI PL09000 camera at the Sierra Remote Observatory near
Auberry, CA, USA); 10.463, 17.3 (T. Noguchi, Katori, Chiba-ken, Japan; 0.23-m
f/6.3 Schmidt-Cassegrain reflector; position end figures 06s.13, 07".5;
image posted at URL http://park8.wakwak.com/~ngc/images/PSNinNGC7753.jpg;
communicated by Nakano); 13.078, 17.5 (G. Masi; remotely using a 43-cm
telescope at Ceccano, Italy; position end figures 06s.14, 07".4); Sept.
11.885, 17 (F. Mete, Rome, Italy; Celestron 14 reflector + SBIG ST8 camera;
position end figures 06s.17, 06".8).

     L. Tomasella, A. Pastorello, S. Benetti, E. Cappellaro, N. Elias-Rosa,
P. Ochner, L. Tartaglia, G. Terreran, and M. Turatto, Osservatorio Astronomico
di Padova, Istituto Nazionale di Astrofisica, report that an optical
spectrogram (range 340-820 nm; resolution 1.2 nm) of PSN J23470615+2929074 =
SN 2015ae, obtained on Aug. 7.09 UT with the Asiago 182-cm Copernico Telescope
(+ AFOSC) in the framework of the Asiago Transient Classification Program
(Tomasella et al. 2014, AN 335, 841), shows that this was then a young type-II
supernova.  Striking similarity with SN 1999em a few days after the explosion
is found.  Broad Balmer lines and He I 587.6-nm are detected, with P-Cyg
profile.  The velocity of the ejected material, as inferred from the position
of the minimum of H-beta, is about 9000 km/s, if a redshift of 0.0172 is
assumed for the host galaxy, NGC 7753 (Springob et al. 2005, Ap.J. Suppl. 160,
149).  Classification was done with GELATO (Harutyunyan et al. 2008, A.Ap.
488, 383) and SNID (Blondin and Tonry 2007, Ap.J. 666, 1024).  The Asiago
classification spectra are posted at URL http://sngroup.oapd.inaf.it.

     T. Nakaoka, K. Takaki, M. Kawabata, and K. S. Kawabata, Hiroshima
University; and M. Yamanaka, Konan University, obtained a low-resolution
optical spectrum (range 450-900 nm) of PSN J23470615+2929074 = SN 2015ae on
Aug. 7.6 UT with the 1.5-m Kanata telescope (+ HOWPol) at Higashi-Hiroshima
Observatory.  The spectrum shows a blue continuum and a Balmer H-alpha line
having a P-Cyg profile, suggesting that this was then a type-II supernova in
its early phase.  The absorption component of the H-alpha line is blueshifted
by around 9000 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 type-II supernovae at early phases -- e.g., SNe 1992H
and 2012A at 1-2 weeks after their explosions.


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

                         (C) Copyright 2015 CBAT
2015 November 16                 (CBET 4178)              Daniel W. E. Green