Simulating FRB Morphologies and Coherent Phase Correlation Signatures from Multi-Plane Astrophysical Lensing

Abstract

Fast Radio Bursts (FRBs), like pulsars, display radio emission from compact regions such that they can be treated as point sources. As this radiation propagates through space, they encounter sources of lensing such as a gravitational field of massive objects or inhomogeneous changes in the electron density of cold plasma. We have developed a simulation tool to generate these lensing morphologies through coherent propagation transfer functions generated by phase coherent geometric optics on a spatial grid. In the limit an FRB can be treated as a point source, the ray paths from the FRB to the observer are phase coherent. Each image will have a time delay and magnification that will alter the emitted frequency-temporal morphology of the FRB to that which is observed. The interference of these images could also decohere the observed phase properties of the images, affecting any phase related searches such as searching for the auto-correlation of the observed FRB voltage with other images in time. We present analytic test cases to demonstrate that the simulation can model qualitative properties. We provide example multi-plane lensing systems to show the capabilities of the simulation in modeling the lensed morphology of an FRB and observed phase coherence.