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@eps.harvard.edu (alternate cbat@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