SUPERNOVAE POWERED BY MAGNETARS THAT TRANSFORM INTO BLACK HOLES

Rapidly rotating, strongly magnetized neutron stars (NSs; magnetars) can release their enormous rotational energy via magnetic spin-down, providing a power source for bright transients such as superluminous supernovae (SNe). On the other hand, particularly massive (so-called supramassive) NSs require a minimum rotation rate to support their mass against gravitational collapse, below which the NS collapses to a black hole (BH). We model the light curves (LCs) of SNe powered with magnetars that transform into BHs. Although the peak luminosities can reach high values in the range of superluminous SNe, their post maximum LCs can decline very rapidly because of the sudden loss of the central energy input. Early BH transformation also enhances the shock breakout signal from the magnetar-driven bubble relative to the main SN peak. Our synthetic LCs of SNe powered by magnetars transforming to BHs are consistent with those of some rapidly evolving bright transients recently reported by Arcavi et al.