2015MNRAS.454.3311M

Strongly magnetized, rapidly rotating neutron stars are contenders for the central engines of both long gamma-ray bursts (LGRBs) and hydrogen-poor superluminous supernovae (SLSNe-I). Models for typical (minute long) LGRBs invoke magnetars with high dipole magnetic fields (Bd ≳ 10¹⁵ G) and short spin-down times, SLSNe-I require neutron stars with weaker fields and longer spin-down times of weeks. Here, we identify a transition region in the space of Bd and birth period for which a magnetar can power both a LGRB and a luminous supernova. In particular, a 2 ms period magnetar with a spin-down time of ∼ 10⁴ s can explain both the ultralong GRB 111209 and its associated luminous SN2011kl. For magnetars with longer spin-down times, we predict even longer duration ( ∼ 10⁵ - 6 s) GRBs and brighter supernovae, a correlation that extends to Swift J2058+05 (commonly interpreted as a tidal disruption event). We further show that previous estimates of the maximum rotational energy of a protomagnetar were too conservative and energies up to Emax ∼ 1-2x10⁵³ ergs are possible. A magnetar can therefore comfortably accommodate the extreme energy requirements recently posed by the most luminous supernova ASASSN-15lh. The luminous pulsar wind nebula powering ASASSN-15lh may lead to an `ionization breakout' X-ray burst over the coming months, accompanied by a change in the optical spectrum.