[IAUC] CBET 2941: 20111207 : SUPERNOVA 2011iw

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                                                  Electronic Telegram No. 2941
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 2011iw
     A. Mahabal, A. J. Drake, S. G. Djorgovski, M. J. Graham, and R. Williams,
California Institute of Technology; J. L. Prieto, Princeton University; M.
Catelan, Pontificia Universidad Catolica de Chile; E. C. Beshore and S. M.
Larson, Lunar and Planetary Laboratory, University of Arizona; and E.
Christensen, Gemini Observatory, report the discovery of a supernova in
unfiltered Catalina Sky Survey (CSS) images:

    SN       2011 UT        R.A. (2000.0) Decl.      Mag.
    2011iw   Nov. 29.09   23 34 48.20  +24 45 01.6   16.9

Nothing was visible at this position on a CSS image from Sept. 19.35 UT
(limiting mag 19.5).  Spectroscopic follow-up observations (range 400-800 nm)
were taken with the Palomar 5-m telescope on Nov. 29.25.  The spectrum exhibits
strong, narrow Balmer emission lines corresponding to a redshift z = 0.023,
which are superimposed on a blue continuum.  A broad feature is observed near
610 nm that is likely due to He I.  The object is thus identified as a likely
type-IIn supernova.

     L. Tomasella, S. Benetti, A. Pastorello, S. Valenti, and F. Bufano,
Istituto Nazionale di Astrofisica (INAF), Osservatorio Astronomico di Padova;
and G. Altavilla, INAF, Osservatorio Astronomico di Bologna, on behalf of a
larger collaboration and the Gaia Science Alerts Follow-up Programme, report
that spectrograms of 2011iw, obtained on Nov. 30.80 UT with the Asiago 1.82-m
Copernico Telescope (+ AFOSC; range 350-820 nm, resolution 2.4 nm) by the
Service Telescope Operating Team and with the Cassini 1.52-m telescope (+
BFOSC; range 490-800 nm; resolution 1.4 nm) on Nov. 30.81, show it to be a
type-IIn supernova soon after explosion.  The spectrum is dominated by a blue
continuum and intense Balmer emissions with a composite profile.  They consist
of an unresolved component overimposed on a broader line (FWHM about 4000
km/s).  A broad bump (FWHM about 4600 km/s) is also present close to the He I
587.6-nm transition.  The redshift of the supernova (z about 0.0230) has been
derived from the narrow emissions of the Balmer lines.


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                         (C) Copyright 2011 CBAT
2011 December 7                  (CBET 2941)              Daniel W. E. Green