Recent searches by unbiased, wide-field surveys have uncovered a group
of extremely luminous optical transients. The initial discoveries of SN
2005ap by the Texas Supernova Search and SCP-06F6 in a deep Hubble
pencil beam survey were followed by the Palomar Transient Factory
confirmation of host redshifts for three similar transients. The
transients share the common properties of high optical luminosities
(peak magnitudes ~ -21 to -23), blue colors, and a lack of H or He
spectral features. The physical mechanism that produces the luminosity
Pastorello et al. 2010, ApJL, 724, 16
