Two classes of fast-declining Type Ia supernovae

摘要

We aim to characterise a sample of fast-declining Type Ia supernovae (SN?Ia) using their bolometric and near-infrared (NIR) properties. Based on these properties, we find that fast-declining SN Ia separate into two categories based on their bolometric and NIR properties. The peak bolometric luminosity ( L _(max) ), the phase of the first maximum relative to the optical, the NIR peak luminosity, and the occurrence of a second maximum in the NIR distinguish a group of very faint SN?Ia. Fast-declining supernovae show a large range of peak bolometric luminosities ( L _(max) differing by up to a factor of ~ 8). All fast-declining SN?Ia with L _(max) & 0.3 × 10 ~(43) erg s ~(-1) are spectroscopically classified as 91bg-like and show only a single NIR peak. SNe with L _(max) & 0.5 × 10 ~(43) erg s ~(-1) appear to smoothly connect to normal SN?Ia. The total ejecta mass ( M _(ej) ) values for SNe with enough late time data are ? 1? M _(⊙) , indicating a sub-Chandrasekhar mass progenitor for these SNe.