Astronomers have proposed a number of mechanisms to produce supernova
explosions. Although many of these mechanisms are now not considered primary
engines behind supernovae, they do produce transients that will be observed by
upcoming ground-based surveys and NASA satellites. Here we present the first
radiation-hydrodynamics calculations of the spectra and light curves from three
of these "failed" supernovae: supernovae with considerable fallback, accretion
induced collapse of white dwarfs, and energetic helium flashes (also known as
type .Ia supernovae).Comment: 33 pages, 14 figure
