GRB 170714A: A good sample for investigating screen of magnetic field?

Abstract

X-ray afterglow of the gamma-ray burst (GRB), GRB 170714A, may exhibit an intriguing characteristic: It comprises two plateaus, each followed by a precipitous decay segment. We posit that this unusual feature can be rationalized within the framework of GRB magnetar scenario. Specifically, initial break in the X-ray afterglow is attributed to the decay of magnetic field of the central magnetar, whereas the subsequent break corresponds to the collapse of this magnetar. We argue that the decay of magnetar’s magnetic field is caused by the fall-back accretion. Given this current understanding, we deduce that rare hypercritical fall-back accretion is layered, with density profile of the fallback matter along the radial direction being notably discontinuous. Our work potentially shows the prospect of employing GRBs as a tool to investigate intricacies of highly uncertain fall-back accretion processes.