Quasi-perpendicular shock acceleration and TDE radio flares

TL;DR

This paper proposes that quasi-perpendicular shocks caused by TDE outflows interacting with the circumnuclear medium can explain the delayed radio flares observed in optical TDEs, highlighting a specific particle acceleration mechanism.

Contribution

It introduces a theoretical model showing that quasi-perpendicular shocks produce steep particle spectra consistent with observed TDE radio flares, advancing understanding of TDE outflow interactions.

Findings

Synchrotron spectral indices match theoretical predictions.

Quasi-perpendicular shocks produce steeper particle spectra.

Particle acceleration explains delayed TDE radio emission.

Abstract

Delayed radio flares of optical tidal disruption events (TDEs) indicate the existence of non-relativistic outflows accompanying TDEs. The interaction of TDE outflows with the surrounding circumnuclear medium creates quasi-perpendicular shocks in the presence of toroidal magnetic fields. Because of the large shock obliquity and large outflow velocity, we find that the shock acceleration induced by TDE outflows generally leads to a steep particle energy spectrum, with the power-law index significantly larger than the "universal" index for a parallel shock. The measured synchrotron spectral indices of recently detected TDE radio flares are consistent with our theoretical expectation. It suggests that the particle acceleration at quasi-perpendicular shocks can be the general acceleration mechanism accounting for the delayed radio emission of TDEs.