2009CBET.2086....1C

R. Chornock and E. Berger, Harvard-Smithsonian Center for Astrophysics, report that a spectrum (range 470-890 nm) of 2009mk (cf. CBET 2080), taken on Dec. 19.16 UT with GMOS on the Gemini-South telescope, reveals that the object is a type-IIb supernova. Cross-correlation with a library of supernova spectra using the "SuperNova IDentification" code (SNID; Blondin and Tonry 2007, Ap.J. 666, 1024) indicates that 2009mk is most similar to SN 1996cb near maximum light. Strong H-alpha absorption is present, with the absorption minimum blueshifted by 13500 km/s, as well as additional absorptions from He I.