[IAUC] CBET 4181: 20151116 : SUPERNOVA 2015ah IN UGC 12295 = PSN J23002463+0137368

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                                                  Electronic Telegram No. 4181
Central Bureau for Astronomical Telegrams
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SUPERNOVA 2015ah IN UGC 12295 = PSN J23002463+0137368
     Vladimir Lipunov and Oleg Gress reported the discovery of an possible
supernova (mag 15.9) on three unfiltered CCD images (limiting mag 19.5) taken
with the MASTER-Kislovodsk auto-detection system (twin 0.40-m f/2.5 reflector)
on Aug. 6.902-6.918 UT.  The new object is located at R.A. = 23h00m24s.63,
Decl. = +1d37'36".8 (equinox 2000.0), which is 13".8 east and 1".4 north of
the center of UGC 12295.  E. Gorbovskoy, A. Tlatov, and N. Tiurina report (via
Lipunov) that nothing was visible at this position on MASTER-Kislovodsk images
obtained on 2010 Nov. 6.75 (limiting mag 20.8).  The discovery images are
posted at http://master.sai.msu.ru/static/OT/MASTEROTJ230024.63013736.8.png.
The variable was designated PSN J23002463+0137368 when it was posted at the
Central Bureau's TOCP webpage and is here designated SN 2015ah based on the
spectroscopic confirmation reported below.  Additional CCD magnitudes for
2015ah:  Aug. 8.036, V = 16.8 (M. Martignoni, Magnago, Italy; 25-cm f/10
Schmidt-Cassegrain reflector; position end figures 24s.66, 36".7); 8.273,
17.3 (J. Brimacombe, Cairns, Australia; image posted at website URL
https://www.flickr.com/photos/43846774@N02/20452697806/); 13.071, 16.5 (G.
Masi; remotely using a 43-cm telescope at Ceccano, Italy; position end
figures 24s.67, 36".8).

     S. Valenti, I. Arcavi, G. Hosseinzadeh, C. McCully, and D. A. Howell,
Las Cumbres Observatory Global Telescope Network and University of California,
Santa Barbara, report that a spectrogram of PSN J23002463+0137368 = SN 2015ah,
obtained on Aug. 9.42 UT with the FLOYDS robotic spectrograph (range 320-1000
nm, resolution 2 nm) mounted on the 2-m "Faulkes Telescope North" at
Haleakala Observatory, Hawaii, shows it to be a peculiar type-Ib supernova.
Using SNID (Blondin and Tonry 2007, Ap.J. 666, 1024), they find a good fit to
the peculiar type-Ib supernova 2005bf a few days before maximum light at the
redshift of the proposed host galaxy, UGC 12295 (z = 0.016; Falco et al. 1999,
PASP 111, 438; via NED).  "Superfit" software (Howell et al. 2005, Ap.J. 634,
1190) finds a reasonable match to the type-Ib supernova 1999ex at a few days
after peak (though at slower expansion velocities than seen in this spectrum)
at the same redshift.  The spectrogram displays He I absorption features that
are consistent with an expansion velocity of 8000 km/s and Fe II at 9000 km/s
(SN 2005bf also had the peculiar property of higher-velocity Fe II compared
to He I).  An absorption feature around rest wavelength 622.0 nm (also seen
for SN 2005bf) is consistent with Si II at 6000 km/s or H-alpha at 16000
km/s.  Additional follow-up of this peculiar supernova is encouraged.

     T. Nakaoka, K. Takaki, M. Kawabata, and K. S. Kawabata, Hiroshima
University; and M. Yamanaka, Konan University, obtained a low-resolution
optical spectrogram (range 450-900 nm) of PSN J23002463+0137368 = SN 2015ah
on Aug. 7.6 UT with the 1.5-m Kanata telescope (+ HOWPol) at the Higashi-
Hiroshima Observatory.  The spectrum shows absorption of He I (587.6- and
667.8-nm) and the Balmer H-alpha line, suggesting that this is a type-IIb
supernova.  The absorption component of the H-alpha line is blueshifted by
around 15000 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 the type-IIb supernova 2008ax around B-band maximum
light.


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                         (C) Copyright 2015 CBAT
2015 November 16                 (CBET 4181)              Daniel W. E. Green