Magnetar-Powered Transients

In this talk, I will review recent studies of magnetar-powered transients. These phenomena include gamma-ray burst afterglows and superluminous supernovae. For short gamma-ray bursts, I will discuss implications of magnetars left behind by the merger of two neutron stars. This central engine would be testable with future observations of gravitational waves and polarization of multi-waveband electromagnetic emission. I will also discuss some energy source models for superluminous supernovae, and in particular, I will show that ASASSN-15lh-like superluminous supernovae provide a signature for the birth of a strange quark star.