Years Delayed Gamma-ray and Radio Afterglows Originated from TDE Wind-Torus Interactions

TL;DR

This paper predicts delayed gamma-ray and radio afterglows from TDE wind-torus interactions, driven by shocks that accelerate particles and produce observable high-energy emissions years after the initial event.

Contribution

It introduces a model for years delayed gamma-ray and radio afterglows from TDE wind-torus interactions, highlighting the role of shocks in producing high-energy emissions.

Findings

Gamma-ray luminosity can reach 10^{41} erg/s depending on wind kinetic luminosity.

Radio afterglow at 1-10 GHz can reach 10^{38-39} erg/s with strong magnetic fields.

Infrared emission extends from the shocks, reaching 10^{39-40} erg/s.

Abstract

Tidal disruption events (TDEs) that occur in active galactic nuclei (AGN) with dusty tori are a special class of sources. TDEs can generate ultrafast and large opening-angle wind, which will almost inevitably collide with the preexisting AGN dusty tori a few years later after the TDE outburst. The wind-torus interactions drive two kinds of shocks: the bow shocks at the windward side of the torus clouds, and the cloud shocks inside the torus clouds. In a previous work, we proved that the shocked clouds will give rise to considerable X-ray emissions which can reach $10^{41-42}$ erg s$^{-1}$ (so called \emph{years delayed X-ray afterglows}). In this work, we focus on the radiations of high energy particles accelerated at both shocks. Benefitting from the strong radiation field at the inner edge of the torus, the inverse Compton scatterings of AGN photons by relativistic electrons at bow shocks dominate the overall gamma-ray radiation. The gamma-ray luminosity can reach $10^{41}~{\rm erg s^{-1}} (L_{\rm kin}/10^{45}{\rm erg s^{-1}})$, where $L_{\rm kin}$ is the kinetic luminosity of TDE wind. Synchrotron radiation at bow shocks contributes to the radio afterglow with a luminosity of 10$^{38-39} ~{\rm erg s^{-1}} (L_{\rm kin}/10^{45}{\rm erg s^{-1}})$ at 1-10 GHz if the magnetic field is 100 mGauss, and extends to infrared with a luminosity of $\sim 10^{39-40}~{\rm erg s^{-1}} (L_{\rm kin}/10^{45}{\rm erg s^{-1}})$. Our scenario provides a prediction of the years delayed afterglows in multiple wavebands for TDEs and reveals their connections.