[IAUC] CBET 2789: 20110821 : PSN J12304185+4137498 IN NGC 4490

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                                                  Electronic Telegram No. 2789
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


PSN J12304185+4137498 IN NGC 4490
     Giancarlo Cortini and Stefano Antonellini, Predappio, Italy, report their
discovery of an apparent supernova (mag 16.7) on several unfiltered CCD frames
(limiting mag about 18.0) taken around Aug. 16.83 UT.  The new object is
located at R.A. = 12h30m41s.85, Decl. = +41d37'49".8 (equinox 2000.0), which
is 57" east and 37" south of the center of NGC 4490.  Nothing is visible at
this position on their previous images taken of this galaxy or on Palomar Sky
Survey red and blue plates (no dates or limiting magnitudes provided).  The
variable was designated PSN J12304185+4137498 when posted on the Central
Bureau's TOCP webpage.  Additional unfiltered CCD magnitudes reported for
2011fd:  Aug. 17.80, 17.5 (T. Borkovits and R. Szakats, Baja Observatory,
Hungary; three stacked 60-s images taken with the BART telescope; image posted
at URL http://titan.physx.u-szeged.hu/~sn/psn_j12304185+4137498_bajaobs.jpg);
20.168, 16.8 (Joseph Brimacombe, Cairns, Australia; position end figures
41s.87, 49".3; image at http://www.flickr.com/photos/43846774@N02/6062934887/).

     L. Magill, R. Kotak, M. Fraser, and S. Smartt, Queen's University,
Belfast; and P. Ochner, A. Pastorello, and S. Benetti, Osservatorio Astronomico
di Padova, Istituto Nazionale di Astrofisica, report that optical spectra of
PSN J12304185+4137498 were obtained at the Telescopio Nazionale Galileo using
the LRS instrument by A. Harutunyan on Aug. 18.9 and 19.9 UT with spectral
ranges 520-910 and 350-800 nm, respectively.  The spectrum is dominated by
narrow Balmer lines in emission, superimposed on a relatively blue continuum.
The FWHM of the H_alpha feature -- which does not exhibit a multi-component
profile -- is about 1200 km/s.  The only other features apparent are most
likely due to a blend of Fe II features between 510 and 550 nm, and a feature
at 454 nm that is also due to Fe II.  The spectrum is reminiscent of that of
a supernova impostor, but they note that -- on the basis of available
positional information -- they find no nearby source consistent with an
unextinguished luminous blue variable in pre-explosion optical WFPC2 images
from the Hubble Space Telescope, while mid-infrared data from Spitzer (+
IRAC) would appear to disfavor a luminous, dust-enshrouded progenitor.


NOTE: These 'Central Bureau Electronic Telegrams' are sometimes
      superseded by text appearing later in the printed IAU Circulars.

                         (C) Copyright 2011 CBAT
2011 August 21                   (CBET 2789)              Daniel W. E. Green