One-dimensional General Relativistic Particle-in-cell Simulations of Stellar-mass Black Hole Magnetospheres: A Semianalytic Model of Gamma-Rays from Gaps

In the absence of a sufficient amount of plasma injection into the black hole (BH) magnetosphere, the force-free state of the magnetosphere cannot be maintained, leading to the emergence of strong, time-dependent, longitudinal electric fields (i.e., spark gaps). Recent studies of supermassive BH magnetospheres using analytical methods and particle-in-cell (PIC) simulations propose the possibility of efficient particle acceleration and consequent gamma-ray emission in the spark gap. In this work, we perform 1D general relativistic PIC simulations to examine the gamma-ray emission from stellar-mass BH magnetospheres. We find that intermittent spark gaps emerge and particles are efficiently accelerated in a similar manner to the supermassive BH case. We build a semianalytic model of the plasma dynamics and radiative processes, which reproduces the maximum electron energies and peak gamma-ray luminosities of the simulation results. Based on this model, we show that the gamma-ray signals from stellar-mass BHs wandering through the interstellar medium could be detected by gamma-ray telescopes such as the Fermi Large Area Telescope or the Cherenkov Telescope Array.