Stars Bisected by Relativistic Blades

Abstract

We consider the dynamics of an equatorial explosion powered by a millisecond magnetar formed from the core collapse of a massive star. We study whether these outflows -- generated by a priori magneto-centrifugally-driven, relativistic magnetar winds -- might be powerful enough to produce an ultra-relativistic blade ("lamina") that successfully carves its way through the dense stellar interior. We present high-resolution numerical special-relativistic hydrodynamic simulations of axisymmetric centrifugally-driven explosions inside a star and follow the blast wave propagation just after breakout. We estimate the engine requirements to produce ultra-relativistic lamina jets and comment on the physicality of the parameters considered. We find that sufficiently collimated -- half-opening angle $\theta_r \leq 0.2^\circ$ -- laminas successfully break out of a compact progenitor at ultra-relativistic velocities ($\Gamma_{\rm core} \gtrsim 30$) and extreme isotropic energies ($E_{k,\rm iso} \sim 5 \times 10^{52}\text{erg}$) within a few percent of the typical spin-down period for a millisecond magnetar. The various phases of these ultra-thin outflows such as collimation shocks, Kelvin-Helmholtz instabilities, and lifetime are discussed and we speculate on the observational signatures echoed by this outflow geometry.