2011CBET.2824....2C

A spectrum, obtained on Sept. 22.23 UT with the 9.2-m Hobby-Eberly Telescope (+ Marcario Low-Resolution Spectrograph) by J. Caldwell, shows that 2011fr is most probably a type-IIn supernova. The spectrum consists of emission features of H and He I, superimposed on a blue continuum. An active-galactic-nucleus outburst can be ruled out since the source is clearly off-centered within the galaxy on the HET finder images. The H emission profiles are of Lorentzian shape, having FWHMs of 1200, 1500, and 2000 km/s for H-alpha, H-beta, and H-gamma, respectively. No P-Cygni component can be detected for any of the observed emission features. The redshift estimated from the emission peaks is z = 0.0596, which is consistent with the photo-z of the presumed host galaxy in the SDSS database. Adopting this redshift, the brightness measured by ROTSE corresponds to absolute magnitude -19.1, which is brighter than most core-collapse supernovae, being close to the peak brightness of type-Ia supernovae. This suggests that interaction between ejecta and circumstellar material may contribute significantly to the observed luminosity. Although the appearance of the spectrum is similar to that of the super-luminous supernova 2008am (Chatzopoulos et al. 2011, Ap.J. 729, 143), the observed brightness is below the fiducial lower limit (mag -20) of such extreme events.