Electronic Telegram No. 2976 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 J12355230+2755559 IN NGC 4559 Further to CBET 2929, M. Kandrashoff, S. B. Cenko, W. Li, and A. V. Filippenko report the LOSS discovery of a possible supernova (mag 16.7) on unfiltered KAIT images taken on Jan. 11.54 UT; the object was found to be located at R.A. = 12h35m52s.30, Decl. = +27d55'55".9 (equinox 2000.0), which is 71" west and 103" south of the center of NGC 4559. The variable was designated PSN J12355230+2755559 when it was posted at the Central Bureau's TOCP webpage. Cenko noted that the variable may be associated with one of the satellite galaxies of NGC 4559 (noting that there are a few faint ones nearby, all being at approximately the same redshift). Additional CCD magnitudes for PSN J12355230+2755559 (unfiltered unless noted otherwise): 1990 Mar. 23, [19.5 (Simone Leonini, Siena, Italy; Palomar Sky Survey, N plate); 2010 Apr. 29, [19.0 (Leonini et al., Montarrenti Observatory, in the course of an automatic survey of the Italian Supernovae Search Project using a 0.53-m f/8.7 Ritchey-Chretien telescope + Apogee Alta U47 CCD camera); 2011 Jan. 9.54 UT, [18.0 (KAIT); 11.251, 16.5 (Leonini, with G. Guerrini, P. Rosi, and L. M. Tinjaca Ramirez; pre-discovery images; limiting mag about 18.2; position end figures 52s.25, 55".9); 12.40, 16.4 (KAIT); 13.449, R = 17.7 (Joseph Brimacombe, Cairns, Australia; using a 51-cm RCOS telescope + STL11K camera + red filter at the New Mexico Skies Observatory near Mayhill, NM; position end figures 52s.29, 55".9); 14.529, 18.6 (Brimacombe; luminance filter; image posted at website URL http://www.flickr.com/photos/43846774@N02/6700504855/). A. Pastorello, E. Cappellaro, and S. Benetti, Istituto Nazionale di Astrofisica, Osservatorio Astronomico di Padova; and A. Harutunyan, Telescopio Nazionale Galileo, report that an optical spectrum (range 350-800 nm; resolution 1 nm) of PSN J12355230+2755559 was obtained at the Telescopio Nazionale Galileo (+ LRS) on Jan. 14.1 UT; the weather conditions were not optimal. The noisy spectrum shows a relatively blue continuum dominated by narrow emissions of the H Balmer series with a FWHM of about 1000 km/s and centered at a redshift of about 800 km/s. The spectrum is very similar to that of the "supernova impostor" 2009ip (Smith et al. 2010, A.J. 139, 1451), and therefore it is most likely the outcome of the eruption of a luminous blue variable (LBV). J. Vinko, University of Szeged; G. H. Marion, Harvard-Smithsonian Center for Astrophysics; and J. C. Wheeler, University of Texas, report that a spectrum of PSN J12355230+2755559 was obtained on Jan. 14.4 UT with the 9.2-m Hobby-Eberly Telescope (+ Marcario Low-Resolution Spectrograph) by Sergey Rostopchin. The spectrum is dominated by a blue continuum with very strong, narrow emission features of H I, [O III] 495.9-nm, and [O III] 500.7-nm. The FWHM of the H-alpha feature is 900 km/s. There is a weaker, but significantly detected feature at 590.0 nm that could be due to either He I 587.5-nm or Na I D. There is no sign of features due to permitted transitions of O I or Ca II. The redshift derived from the strong emission lines is 0.003, which matches the redshift of the proposed host galaxy, NGC 4559. The spectrum shows strong resemblance with Luminous Blue Variable outbursts ("supernova mpostors"; Van Dyk et al. 2000, PASP 112, 1532; Smith et al. 2009, Ap.J. 697, L49). The absolute magnitude of the transient (using the average distance of 8.5 Mpc for the host from NED) is about -13, which is within the observed range for such events. NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2012 CBAT 2012 January 16 (CBET 2976) Daniel W. E. Green