Electronic Telegram No. 2799 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 SUPERNOVA 2011fh IN NGC 4806 L. A. G. Monard, Calitzdorp, Western Cape, South Africa, reports his discovery of an apparent supernova (mag 14.5) on unfiltered CCD images taken on Aug. 24.746 and 25.716 UT at the Klein Karoo Observatory. The new object is located at R.A. = 12h56m14s.01, Decl. = -29d29'54".8 (equinox 2000.0), which is 14" east and 21" north of the core of the galaxy NGC 4806; this position coincides closely with a dense region of the galaxy that has a starlike appearance (as seen on a red Digitized Sky Survey image). Photometric measurements on archived images taken at the Klein Karoo Observatory on several occasions in 2011 showed a brightening of this region starting around 2011 Feb. 11.190 (mag 17.0) and gradually brightening to mag 16.4 around June 2.812 and to mag 16.0 on Aug. 2.710 (which was the last observation prior to the discovery on Aug. 24). J. L. Prieto, Carnegie Observatories, reports than an optical spectrum (range 370-930 nm; resolution 0.7 nm) of 2011fh was obtained on Aug. 29.0 with the du Pont 2.5-m telescope (+ WFCCD) at Las Campanas Observatory. The spectrum has a blue continuum and strong emission lines from the Balmer series that show multiple velocity components, which are characteristic of type-IIn supernovae. The H-alpha profile can be well-fitted with three Gaussian components, including a narrow unresolved component and two relatively broad resolved components with FWHM = 1600 and 7400 km/s. Analysis of archival pre-explosion Spitzer/IRAC 3.6- and 4.5-micron images of the host galaxy (NGC 4806), obtained in 2009 Aug. and Sept. (Program ID 60007, PI K. Seth) show a mid-infrared point source at the position of 2011fh with flux densities 0.12 mJy (mag 15.9) at 3.6 microns and 0.11 mJy (mag 15.5) at 4.5 microns. At the distance of NGC 4806 (via NED; 33 Mpc from Virgo-infall corrected velocity), these values imply luminosity densities of 3.5 x 10**6 and 2.5 x 10**6 solar luminosity at 3.6 and 4.5 microns, respectively. If this is a single source, it would imply a very massive progenitor star. However, note that the spatial resolution of the Spitzer/IRAC images is approximately 260 pc (FWHM) at the distance of NGC 4806, and this source could be an H II region. NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2011 CBAT 2011 August 31 (CBET 2799) Daniel W. E. Green