calcium-rich gap transient

A calcium-rich gap transient (or calcium-rich supernova) is an observed transient rich in calcium spectral lines, that (generally?) falls in the gap in luminosity between a nova and supernova, They show differences from both core collapse supernovae and Type Ia supernovae, their spectra most similar to Type Ib or Type Ic supernovae. They often appear away from the galaxy center, even beyond the apparent host galaxy's border. One idea is they reside in nearby ultra-faint dwarf galaxies. Another is that they occur in binary stars affected by a previous supernova that gave them unusual characteristics causing the spectral differences as well as giving them a velocity kick to explain their position.