Electronic Telegram No. 1381 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 2008S IN NGC 6946 R. Wesson, J. Fabbri, and M. Barlow, University College, London; and M. Meixner, Space Telescope Science Institute, on behalf of the 'Survey for Evolution of Emission from Dust in Supernovae' (SEEDS) collaboration, report the detection of the type-IIn supernova 2008S in Spitzer Space Telescope IRAC and MIPS images that were obtained serendipitously on 2008 Feb. 7 UT, five days after the supernova outburst, during scheduled observations of the nearby supernova 2002hh (cf. IAUC 8005). SN 2008S is detected at R.A = 20h34m45s.34, Decl. = +60o05'58".0 (equinox 2000.0; +/- 0".4 in each coordinate), in close agreement with the optical position (CBET 1234). The measured flux densities in mJy at 3.6, 4.5, 5.8, 8.0, and 24 microns are 1.7 +/- 0.3, 2.0 +/- 0.3, 2.7 +/- 0.4, 4.0 +/- 0.4, and 0.4 +/- 0.3, respectively. This spectral-energy distribution (SED) can be fitted by a 500-K black body modified by a dust emissivity that is inversely proportional to wavelength, giving a luminosity of 2.1 x 10^6 solar luminosities for a distance of 5.6 Mpc to the host galaxy NGC 6946. The progenitor of SN 2008S was detected in archival Spitzer images by Prieto et al. (2008, http://arxiv.org/abs/0803.0324v3), who found that a 440-K blackbody with a luminosity of 3 x 10^4 solar luminosities could fit the progenitor's infrared SED. NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2008 CBAT 2008 May 20 (CBET 1381) Daniel W. E. Green