Time Scales in Tidal Disruption Events

TL;DR

This paper investigates the timing features of tidal disruption events, linking observed lightcurve transitions to the physical processes and object types involved, particularly highlighting the case of Swift J1644+57 and the role of white dwarfs.

Contribution

It introduces a framework connecting lightcurve features with physical time scales, constraining the nature of disrupted objects and accretion processes in tidal disruption events.

Findings

Swift J1644+57's rapid flares suggest a white dwarf disruption.

Transition in Swift J2058+05's light curve may indicate Eddington accretion rate change.

Hydrodynamic time scales limit the rise time of tidal disruption events.

Abstract

We explore the temporal structure of tidal disruption events pointing out the corresponding transitions in the lightcurves of the thermal accretion disk and of the jet emerging from such events. The hydrodynamic time scale of the disrupted star is the minimal time scale of building up the accretion disk and the jet and it sets a limit on the rise time. This suggest that Swift J1644+57, that shows several flares with a rise time as short as a few hundred seconds could not have arisen from a tidal disruption of a main sequence star whose hydrodynamic time is a few hours. The disrupted object must have been a white dwarf. A second important time scale is the Eddington time in which the accretion rate changes form super to sub Eddington. It is possible that such a transition was observed in the light curve of Swift J2058+05. If correct this provides intersting constraints on the parameters of the system.