# Radio Emission from the unbound Debris of Tidal Disruption Events

## TL;DR

This paper investigates how the interaction of unbound stellar debris with ambient medium in tidal disruption events produces observable radio emissions, using numerical simulations to connect debris dynamics with observed signals.

## Contribution

It introduces a simulation-based model linking debris-shock interactions to radio emissions in TDEs, providing insights into debris evolution and ambient gas density.

## Key findings

- Faster and wider outflows occur with smaller periapse distances.
- A TDE with periapse 7 times smaller than the tidal radius explains observed radio emission.
- The model refines estimates of the ambient gas density around the galaxy center.

## Abstract

When a star gets too close to a supermassive black hole, it is torn apart by the tidal forces. Roughly half of the stellar mass becomes unbound and flies away at tremendous velocities - around $10^4$ km/s. In this work we explore the idea that the shock produced by the interaction of the unbound debris with the ambient medium gives rise to the synchrotron radio emission observed in several TDEs. We use a moving mesh numerical simulation to study the evolution of the unbound debris and the bow shock around it. We find that as the periapse distance of the star decreases, the outflow becomes faster and wider. A tidal disruption event whose periapse distance is a factor of 7 smaller than the tidal radius can account for the radio emission observed in ASASSN-14li. This model also allows us to obtain a more accurate estimate for the gas density around the centre of the host galaxy of ASASSN-14li.