Electronic Telegram No. 2279 Central Bureau for Astronomical Telegrams INTERNATIONAL ASTRONOMICAL UNION CBAT Director: Daniel W. E. Green; Room 209; Dept. of Earth and Planetary Sciences; Harvard University; 20 Oxford St.; Cambridge, MA 02138; U.S.A. e-mail: cbat@iau.org; cbatiau@eps.harvard.edu URL http://www.cfa.harvard.edu/iau/cbat.html SUPERNOVA 2010cn G. Folatelli, Universidad de Chile; and M. Stritzinger, Carnegie Observatories, on behalf of the Carnegie Supernova Project and the Millennium Center for Supernova Science, report that a spectrum (range 390-812 nm) of supernova 2010cn (cf. CBETs 2269, 2270, 2272), obtained with the Gemini South Telescope (+ GMOS) on May 8.1 UT, reveals it to be most similar to the type-Ib supernova 2008D (cf. CBETs 1202, 1205, 1222). The spectrum consists of a blue continuum with broad absorption features. Reddening the spectrum by E(B-V) = 0.8 mag shows that it is similar to SN 2008D at six days after explosion (Malesani et al. 2009, Ap.J. 692, L84). Nevertheless, at the present time, 2010cn does not exhibit prevalent absorption related to Fe II multiplet 42 (rest 492.4, 501.8, and 516.9 nm). Emission lines from the host galaxy of 2010cn confirm the redshift of 0.026 given on previous CBETs. Based on this redshift, an absorption at about 630 nm would imply an expansion velocity of 18000 km/s if the line is attributed to H-alpha; if attributed to the Si II 635.5-nm doublet, then the velocity would be around 9000 km/s. Another absorption observed at 570 nm yields a velocity of 15000 km/s if attributed to He I 587.6-nm. NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2010 CBAT 2010 May 13 (CBET 2279) Daniel W. E. Green