Electronic Telegram No. 1242 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 SUPERNOVAE 2008U AND 2008X S. Blondin, Harvard-Smithsonian Center for Astrophysics (CfA), on behalf of the CfA Supernova Group, reports that a spectrum (range 350-740 nm) of 2008U (cf. CBET 1238), obtained on Feb. 8.46 UT by M. Calkins with the F. L. Whipple Observatory 1.5-m telescope (+ FAST), shows it to be either a reddened type-IIn supernova or an outburst of a luminous blue variable (LBV). The spectrum consists of a reddened continuum and narrow Balmer emission lines (FWHM about 300 km/s), as well as other emission lines from the underlying host galaxy. The H_alpha emission line has a broader (FWHM about 3000 km/s) component not present in the other Balmer lines. While this may be the signature of a supernova-like event, adopting a recession velocity of 1948 km/s for the host galaxy (from The Updated Zwicky Catalog, http://tdc-www.harvard.edu/uzc/), and assuming no peculiar motion, the discovery magnitude of 18.4 corresponds to an absolute magnitude of roughly -15, which is more consistent with an LBV than a supernova (cf. also SN 1997bs: Van Dyk et al. 2000, PASP 112, 1532). Blondin et al. add that a spectrum (range 350-740 nm) of 2008X (cf. CBET 1239), obtained as above on Feb. 8.43 UT by Calkins, shows it to be a type-II-plateau supernova, 3-4 weeks past explosion. Cross-correlation with a library of supernova spectra using the "Supernova Identification" code (SNID; Blondin and Tonry 2007, Ap.J. 666, 1024) indicates that 2008U is most similar to the type-II-plateau supernova 2005cs at 3 weeks past explosion. Adopting a recession velocity of 3730 km/s for the host galaxy of 2008U (from The Updated Zwicky Catalog), the maximum absorption in the H_alpha line (rest 656.3 nm) is blueshifted by roughly 4000 km/s. NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2008 CBAT 2008 February 8 (CBET 1242) Daniel W. E. Green