Particle Acceleration from the Intrabinary Shock in Spider Pulsars

Relativistic collisionless shocks are efficient sites of particle acceleration, producing broad nonthermal spectra with power-law distributions. One such example is expected from compact binary systems composed of a millisecond pulsar and a low mass companion, colloquially known as “Spider” pulsars. The relativistic and strongly magnetized pulsar wind impacts onto the companion, ablating it and slowly consuming its atmosphere. This interaction gives rise to the formation of an intrabinary shock, a proposed site of particle acceleration and nonthermal emission. Using TRISTAN-MP we perform global, fully kinetic particle-in-cell simulations of the interaction of a striped pulsar wind with a companion star. We present an analysis of the different mechanisms responsible for accelerating particles, focusing on the interplay between magnetic reconnection and the first- and second-order Fermi processes. Our first-principles synchrotron spectra and lightcurves show good agreement with X-ray observations if the system’s orbital angular momentum is nearly aligned with the pulsar spin axis.