A Calcium-Rich Gap Transient (or Calcium-rich Supernova)
is an observed Transient
within the gap in transient-sizes between a Nova and Supernova,
that is rich in Calcium Spectral Lines.
No model is yet fully accepted, but typical supernova explanations
(core collapse and thermonuclear explosion) are generally rejected.
Extant theories involve White Dwarves and/or Neutron Stars
or even a merger of both.