A LARGE MASS OF IRON IN SUPERNOVA 1991T

We present quantitative intensity measurements of several forbidden transitions of Fe II and Fe III in the spectrum of the type Ia supernova 1991T at age 1 yr. The two species account for virtually the entire observed optical and near-infrared spectrum. These data are fundamental to tests of the explosion models of supernovae, and allow a direct determination of the mass of Ni-56 produced. The line intensities support models that require most of the white dwarf precursor to be converted to Ni-56.