Long-term X-ray emission from Swift J1644+57

TL;DR

This paper models the complex, pulsed X-ray emission of Swift J1644+57 as reverse shocks from shell collisions, successfully fitting the observed light curve and spectrum with a detailed shock model.

Contribution

It introduces a novel reverse shock model to explain the pulsed X-ray emission and fits the observed data with specific parameter choices.

Findings

The model reproduces the pulse structure of the X-ray light curve.

The spectral features are well-matched by the shock emission.

The decline in pulse amplitudes is explained by shock dynamics.

Abstract

The X-ray emission from Swift J1644+57 is not steadily decreasing instead it shows multiple pulses with declining amplitudes. We model the pulses as reverse shocks from collisions between the late ejected shells and the externally shocked material, which is decelerated while sweeping the ambient medium. The peak of each pulse is taken as the maximum emission of each reverse shock. With a proper set of parameters, the envelope of peaks in the light curve as well as the spectrum can be modelled nicely.