[IAUC] CBET 4187: 20151118 : SUPERNOVA 2015am IN UGC 1641 = PSN J02090990+3159515

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                                                  Electronic Telegram No. 4187
Central Bureau for Astronomical Telegrams
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SUPERNOVA 2015am IN UGC 1641 = PSN J02090990+3159515
     Paolo Campaner reports the discovery of an apparent supernova (mag 18.7)
on three 75-s unfiltered CCD exposures (limiting magnitude 20.0) obtained on
Aug. 13.081 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. = 2h09m09s.90, Decl. = +31d59'51".5 (equinox 2000.0), which is 3" west
and 12" north of the center of UGC 1641.  The variable was designated PSN
J02090990+3159515 when it was posted at the Central Bureau's TOCP webpage
and is here designated SN 2015am based on the spectroscopic confirmation
reported below.  G. Masi writes that images obtained remotely on Aug. 13.97
using a 43-cm telescope at Ceccano, Italy, show 2015am at mag 18.6 with
position end figures 09s.87, 53".0.

     P. Ochner, Osservatorio Astronomico di Padova, Istituto Nazionale di
Astrofisica; M. Berton, Dipartimento Fisica e Astronomia, Universita di
Padova; and A. Pastorello, S. Benetti, E. Cappellaro, N. Elias-Rosa, L.
Tartaglia, G. Terreran, 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 J02090990+3159515 =
SN 2015am, obtained on Aug. 13.98 UT with the Asiago 182-cm Copernico
Telescope (+ AFOSC) in the framework of the Asiago Transient Classification
Program (Tomasella et al. 2014, A.N. 335, 841), shows that this a type-II
supernova, few weeks after maximum light.  The spectrum shows P-Cyg lines of
H, Fe II, and Na I that are typically observed in type-II supernovae during
the H-recombination phase.  However, these lines in 2015am are very narrow.
The expansion velocity of the ejecta is very low, when compared (for example)
with the low-velocity type-IIP supernova 2005cs (Pastorello et al. 2009,
MNRAS 394, 2266).  From the minimum of H-alpha, the authors infer an ejecta
velocity of about 2100 km/s when adopting for the host galaxy (UGC 1641) a
redshift z = 0.0167 (from de Vaucouleurs et al. 1991, RC3.9; via NED); they
also measured a velocity of the ejecta of 1700 km/s from the minimum of
H-beta (so slightly lower than that for H-alpha).  The classification was
done with SNID (Blondin and Tonry 2007, Ap.J. 666, 1024).  The Asiago
classification spectra are posted at URL http://sngroup.oapd.inaf.it.


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                         (C) Copyright 2015 CBAT
2015 November 18                 (CBET 4187)              Daniel W. E. Green