On the spectrum of the peculiar type Ia supernova 1997br and the nature of SN 1991T-like events

Abstract Li et al. presented extensive observational data on the peculiar Type Ia SN 1997br and showed that it resembled the well-known peculiar SN 1991T . We present some results of a direct analysis of the spectra of SN 1997br . We raise the question of whether the Fe III and Ni III features in the early spectra are produced by 54 Fe and 58 Ni rather than by 56 Fe and 56 Ni as usually assumed, and discuss the issue of whether SN 1991T -like events are more powerful versions of normal SNe Ia rather than a physically distinct subgroup of events.