SWIFT J164449.3+573451: a plunging event with the Poynting-flux dominated outflow

TL;DR

This paper investigates the tidal disruption event Swift J164449.3+573451, proposing that magnetic processes dominate the outflow and explaining the observed X-ray emission in terms of accretion rate and magnetic activity.

Contribution

It demonstrates that magnetic activities, such as the Blandford-Znajek process, are likely responsible for the outflow, and links the X-ray luminosity to accretion rate during the event.

Findings

Outflow launched mainly via magnetic activities.

X-ray luminosity proportional to accretion rate.

Periastron distance smaller than disruption radius.

Abstract

Swift J164449+573451 is a peculiar outburst which is most likely powered by the tidal disruption of a star by a massive black hole. Within the tidal disruption scenario, we show that the periastron distance is considerably smaller than the disruption radius and the outflow should be launched mainly via magnetic activities (e.g., Blandford-Znajek process) otherwise the observed long-lasting X-ray afterglow emission satisfying the relation $L_{X}\propto\dot{M}$ can not be reproduced, where $L_{X}$ is the X-ray luminosity and $\dot{M}$ is the accretion rate. We also suggest that $L_{X}\propto\dot{M}$ may hold in the quick decline phase of Gamma-ray Bursts.