Electronic Telegram No. 1780 Central Bureau for Astronomical Telegrams INTERNATIONAL ASTRONOMICAL UNION M.S. 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A. IAUSUBS@CFA.HARVARD.EDU or FAX 617-495-7231 (subscriptions) CBAT@CFA.HARVARD.EDU (science) URL http://www.cfa.harvard.edu/iau/cbat.html SUPERNOVA 2008iy M. Catelan, Pontificia Universidad Catolica de Chile; A. J. Drake, S. G. Djorgovski, A. Mahabal, R. Williams, and M. J. Graham, California Institute of Technology; E. C. Beshore and S. M. Larson, Lunar and Planetary Laboratory, University of Arizona; and E. Christensen, Gemini Observatory, report the CRTS (cf. CBET 1766) discovery of a supernova in unfiltered Catalina Sky Survey (CSS) images: SN 2008 UT R.A. (2000.0) Decl. Mag. 2008iy Sep. 28.12 16 08 37.23 + 4 16 26.7 17.8 The CSS light curve, containing 184 observations between 2005 Apr. 4 and 2009 Apr. 16, shows the explosion occurred between 2007 June 18 and 2007 Oct. 13. The rising part of the light curve is seen to last approximately a year. Additional follow-up was obtained with the Palomar 1.52-m reflector with Gunn filters, yielding the following magnitudes: 2008 Oct. 29.12, g = 18.3, r = 17.2, i = 17.8, z = 17.2; 2009 Mar. 17.33, 18.5, 17.6, 18.2, 17.6; Apr. 18.24, 18.7; 17.8; 18.3; 17.8. Confirming spectra (range 380-900 nm) were obtained using the SMARTS 1.5-m telescope on 2009 Mar. 27 and Apr. 20 UT and reveal Balmer lines (strong H-alpha, H-beta, H-gamma) and He I lines (587.6, 706.5 nm). H-beta exhibits a P-Cyg-like profile. No significant evolution is seen between the two spectra. The spectra closely resemble those of the slowly evolving type-IIn supernova 2007rt at 500 days past explosion (Trundle et al. 2009, http://lanl.arxiv.org/abs/0904.0119). Based on the redshift (z = 0.041) and the Palomar photometry, the peak absolute Gunn r magnitude was about -18.8. Archival GALEX data from 2008 June 5 show a well-detected source at this location in Medium Imaging Survey (MIS) far-ultraviolet (FUV; 135-175 nm) and near-ultraviolet (NUV; 175-300 nm) images, at the following magnitudes: [NUV] = 19.93 +/- 0.04; [FUV] = 21.18 +/- 0.09. Five-sigma detection limits in MIS images are about 22.6 for FUV and about 22.7 for NUV. No source is seen in any earlier All Sky Imaging Survey (AIS) images (5-sigma detection limits in AIS images are about 19.9 for FUV and about 20.8 for NUV), including 2004 May 17, indicating a brightening in AIS/NUV by at least 1 magnitude. Co-added images from the Sloan Digital Sky Survey (all filters) reveal the presence of a possible host galaxy near magnitude r = 23, corresponding to an absolute r magnitude of about -13 at the redshift of 2008iy. NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2009 CBAT 2009 April 26 (CBET 1780) Daniel W. E. Green