A model for the multiwavelength radiation from tidal disruption event Swift J1644+57

TL;DR

This paper presents a model explaining multiwavelength observations of the tidal disruption event Swift J1644+57, showing that inverse-Compton cooling accounts for the flat radio and mm lightcurves despite declining jet energy.

Contribution

The work introduces a model that explains the conflicting observational data by attributing flat radio and mm lightcurves to inverse-Compton cooling, not additional energy input.

Findings

Inverse-Compton cooling explains flat radio and mm lightcurves.

X-ray flux decline correlates with reduced electron cooling.

Jet energy declines as t^{-5/3} from x-ray data.

Abstract

Gamma-ray observations of a stellar tidal disruption event (TDE) detected by the Swift satellite and follow up observations in radio, mm, infrared and x-ray bands have provided a rich data set to study accretion onto massive blackholes, production of relativistic jets and their interaction with the surrounding medium. The radio and x-ray data for TDE Swift J1644+57 provide a conflicting picture regarding the energy in relativistic jet produced in this event: x-ray data suggest jet energy declining with time as t^{-5/3} whereas the nearly flat lightcurves in radio and mm bands lasting for about 100 days have been interpreted as evidence for the total energy output increasing with time. We show in this work that flat lightcurves do not require addition of energy to decelerating external shock (which produced radio and mm emission via synchrotron process), instead the flat behavior is due to inverse-Compton cooling of electrons by x-ray photons streaming through the external shock; the higher x-ray flux at earlier times cools electrons more rapidly thereby reducing the emergent synchrotron flux, and this effect weakens as the x-ray flux declines with time.