[IAUC] CBET 2786: 20110810 : SUPERNOVA 2011ek IN NGC 918

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                                                  Electronic Telegram No. 2786
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
CBAT Director:  Daniel W. E. Green; Hoffman Lab 209; Harvard University;
 20 Oxford St.; Cambridge, MA  02138; U.S.A.
e-mail:  cbatiau en eps.harvard.edu (alternate cbat en iau.org)
URL http://www.cbat.eps.harvard.edu/index.html
Prepared using the Tamkin Foundation Computer Network


SUPERNOVA 2011ek IN NGC 918
     G. H. Marion, Harvard-Smithsonian Center for Astrophysics; J. Vinko,
University of Szeged; and J. C. Wheeler University of Texas at Austin,
report that a spectrum (range 420-1020 nm) of SN 2011ek (cf. CBETs 2783, 2785)
was obtained on Aug. 9.41 UT with the 9.2-m Hobby-Eberly Telescope (+ Marcario
Low Resolution Spectrograph) by S. Rostopchin.  The velocities of Si II at
635.5 and 597.2 nm are higher than the usual value for subluminous (1991bg-
like) type-Ia supernovae at similar epochs.  Measured values of 13200 and
12900 km/s, respectively, are obtained, assuming a redshift of z = 0.005, as
listed by NED (Rhee and van Albada 1996, A.Ap. Suppl. 115, 407) for the
proposed host galaxy, NGC 918.  The line-depth ratio for Si II absorption
features at 635.5 and 597.2 nm [R(Si II)] is about 0.43, which is an
intermediate value that lies between those of SNe 1992A (0.38) and 1986G
(0.53) (Nugent et al. 1995, Ap.J. 455, L147).  O I 777.3-nm and Ca II
857.9-nm produce very strong spectral features, and the continuum is flat --
all of which are consistent with a 1991bg-like type-Ia supernova.
Cross-correlation with a library of supernova spectra using the "Supernova
Identification" code (SNID; Blondin and Tonry 2007, Ap.J. 666, 1024) shows
that 2011ek is a type-Ia supernova near maximum light, but reasonable fits
are found to templates from both normal and 1991bg-like type-Ia supernovae.
The spectrum also shows a narrow, unresolved Na D feature (EW about 0.11 nm),
suggesting significant reddening.  The most recently reported brightness
(mag 16.7 on Aug. 8.5; CBET 2785) is more than 4 magnitudes below the
expected brightness for a normal type-Ia supernova at maximum.


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                         (C) Copyright 2011 CBAT
2011 August 10                   (CBET 2786)              Daniel W. E. Green