2005IAUC.8489....1F

J. Fabbri, University College, London; and B. Sugerman, Space Telescope Science Institute, on behalf of the 'Survey for Evolution of Emission from Dust in Supernovae' (SEEDS) collaboration (M. Barlow, principal investigator), report the detection of the type-II supernova 2004et in archival Spitzer spacecraft 'InfraRed Array Camera' (IRAC) images of NGC 6946 obtained by the 'Spitzer Infrared Nearby Galaxy Survey' (SINGS) Legacy program (cf. Kennicutt et al. 2003, PASP 115, 928) taken on 2004 Nov. 25.7 UT, or 56 days after discovery. A source was detected in all four IRAC bands at R.A. = 20h35m25s.38, Decl. = +60o07'17".8 (equinox 2000.0; ± 0".3 in each coordinate), in close agreement with the optical (IAUC 8413) and radio positions (IAUC 8415). The measured flux densities (mJy) at 3.6, 4.5, 5.8, and 8.0 microns are 21.9 ± 1.7, 13.8 ± 0.8, 10.0 ± 0.4, and 6.7 ± 0.3, respectively. Given the proximity of NGC 6946 (6 Mpc) and the rapid mid-infrared variability of the similarly-aged SN 2004dj (see below), this supernova should be closely monitored at all wavelengths.