[IAUC] CBET 4179: 20151116 : SUPERNOVA 2015af IN NGC 6801 = PSN J19273770+5422340

Lun Nov 16 01:19:56 ART 2015

                                                  Electronic Telegram No. 4179
Central Bureau for Astronomical Telegrams
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Prepared using the Tamkin Foundation Computer Network


SUPERNOVA 2015af IN NGC 6801 = PSN J19273770+5422340
     Paolo Campaner reports the discovery of an apparent supernova (mag 18.4)
on three 75-s unfiltered CCD exposures (limiting magnitude 20.0) obtained on
Aug. 9.024 UT with a 0.4-m f/5.5 reflector at Ponte di Piave, Italy, in the
course of the Italian Supernovae Search Project.  The new object is located at
R.A. = 19h27m37s.70, Decl. = +54d22'34".0 (equinox 2000.0), which is 17" east
and 12" north of the center of NGC 6801.  The variable was designated PSN
J19273770+5422340 when it was posted at the Central Bureau's TOCP webpage and
is here designated SN 2015af based on the spectroscopic confirmation reported
below.  The type-Ia supernova 2011df also appeared on NGC 6801 (cf. CBET
2729).  Additional CCD magnitudes for 2015af:  Aug. 9.875, 18.3 (Campaner);
9.971, 18.3 (J. Grzegorzek, Kolbaskowo, Poland; 0.25-m f/4 reflector; 50-s
exposure; position end figures 37s.74, 32".9; image posted at website URL
http://www.jgao.pl/pgc63229.html); 12.163, 19.0 (J. Brimacombe, Cairns,
Australia; position end figures 37s.70, 32".3; image posted at website URL
https://www.flickr.com/photos/43846774@N02/20342180779/); 13.065, 18.8 (G.
Masi; remotely using a 43-cm telescope at Ceccano, Italy; position end
figures 37s.68, 32".7).

     G. Terreran, S. Benetti, E. Cappellaro, N. Elias-Rosa, P. Ochner, A.
Pastorello, L. Tartaglia, L. Tomasella, and M. Turatto, Osservatorio
Astronomico di Padova, Istituto Nazionale di Astrofisica, report that an
optical spectrogram (range 340-820 nm; resolution 1.4 nm) of PSN
J19273770+5422340 = SN 2015af, obtained on Aug. 10.93 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
a type-II supernova.  Adopting a redshift z = 0.01455 (Springob et al. 2005,
Ap.J. Suppl. 160, 149) for the host galaxy, NGC 6801, the best match is found
with normal type-II supernovae around 10 days after maximum light.  A narrow
H-alpha component, superposed on the broad H-alpha attributed to the
supernova, probably arises from an H II region close to the location of
2015af.  The expansion velocity of the ejected material, as inferred from the
position of the broad absorption of H-alpha, is about 9000 km/s.
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 URL http://sngroup.oapd.inaf.it.


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 4179)              Daniel W. E. Green