ON THE SPECTRUM AND NATURE OF THE PECULIAR TYPE IA SUPERNOVA 1991T

A parametrized supernova synthetic-spectrum code is used to study line identifications in the photospheric-phase spectra of the peculiar Type Ia SN 1991T, and to extract some constraints on the composition structure of the ejected matter. The inferred composition structure is not like that of any hydrodynamical model for Type Ia supernovae. Evidence that SN 1991T was overluminous for a SN Ia is presented, and it is suggested that this peculiar event was probably a substantially super-Chandrasekhar explosion that resulted from the merger of two white dwarfs.