One leading theory suggests that the incredible output of an SLSN is powered by what type of compact object forming at the core?

Answer

A rapidly spinning, highly magnetized neutron star (magnetar)

The Magnetar Engine theory posits that a rapidly spinning, highly magnetized neutron star channels enormous energy into ejected material, powering the extreme brightness.

One leading theory suggests that the incredible output of an SLSN is powered by what type of compact object forming at the core?
galaxyastronomystarssupernovabrightness