Disentangle the physical origin of the thermal-emission decay

Determine whether the early X-ray luminosity decay and shrinking thermal-emitting areas of the magnetar EP J223759.5+531421 are produced predominantly by untwisting-magnetosphere currents, crustal heat diffusion, or a combination of these mechanisms.

Background

The source’s luminosity decreases as the inferred warm and hot emitting regions contract, while their temperatures show no comparably clear monotonic evolution. The paper discusses two principal interpretations: contraction of a current-carrying bundle in an untwisting magnetosphere and thermal energy deposited in the crust that diffuses toward the surface and deeper layers.

Because both mechanisms can produce a fading thermal outburst and may operate simultaneously, the existing broadband and temporal observations do not determine which physical process dominates the observed decay.