A Magnetar is a Neutron Star with a strong magnetic field. The decay of the field powers Emission of X-rays and Gamma Rays. Star quakes can trigger gamma ray flashes, i.e., the source of some longer Gamma-Ray Bursts (GRB).
Magnetars have been observed since 1979 and a theory was put forward in 1992. Circa 2013, 21 magnetars have been identified.
Canadian Institute for Theoretical Astrophysics (CITA)
Superluminous Supernova (SLSN)