2011CBET.2794....2R

A spectrum, obtained on Aug. 24.24 UT with the 9.2-m Hobby-Eberly Telescope (+ Marcario Low-Resolution Spectrograph) by S. Rostopchin, shows that 2011fg is a peculiar type-Ia supernova. The spectrum contains features of Si II, S II, and Fe II, characteristics of type-Ia supernovae, but the strength of the Si II 635.5-nm feature is weaker than normal. O I 777.5-nm and the Ca II infrared triplet are also weakly present. The broad bottom of the Ca II infrared triplet may be indicative of a shallow high-velocity component. The SNID code (Blondin and Tonry 2007, Ap.J. 666, 1024) gives mostly normal type-Ia-supernovae spectra both before and after maximmum as best-fitting templates, but visual inspection reveals a best match with the spectrum of SN 2003fg, a peculiar type-Ia supernova at two days after maximum. The redshift, estimated from the narrow H_alpha feature from the host, is z = 0.045, which agrees with the photometric z value of the host galaxy in the SDSS database. Adopting this redshift estimate, the expansion velocity from the minimum of the Si II 635.5-nm feature is 9000 km/s, lower than for normal type-Ia supernovae around maximum light.