  Type Ia supernovae are thought to result from thermonuclear explosions of
carbon-oxygen white dwarf stars. This model generally explains the observed
properties with certain exceptions, like sub-luminous supernovae. Here we
discuss the possibility of sub-Chandrasekhar WDs detonating due to the build up
of a layer of helium on the C-O WD by accreting from a helium rich companion
star to explain observed deviations such as subluminous type Ia. We also detail
some of the energetics involved that will make such scenarios plausible.
