# Simulating realistic disc formation in tidal disruption events

## TL;DR

This paper presents the first realistic simulation of disc formation in tidal disruption events, revealing how debris evolves into a thick, marginally-bound disc with spiral shocks and an extended envelope, illuminating early TDE radiation.

## Contribution

It introduces a novel simulation approach using outflow initial conditions to model realistic stellar trajectories and black hole masses in TDEs.

## Key findings

- Rapid formation of a thick, marginally-bound disc with spiral shocks.
- Presence of an extended envelope surrounding the accretion flow.
- Shock heating rate consistent with observed TDE luminosities.

## Abstract

A star coming too close to a supermassive black hole gets disrupted by the tidal force of the compact object in a tidal disruption event, or TDE. Following this encounter, the debris evolves into an elongated stream, half of which coming back to pericenter. Relativistic apsidal precession then leads to a self-crossing shock that initiates the formation of an accretion disc. We perform the first simulation of this process considering a realistic stellar trajectory and black hole mass, which has so far eluded investigations for computational reasons. This numerical issue is alleviated by using as initial conditions the outflow launched by the self-crossing shock according the local simulation of Lu & Bonnerot (2019). We find that the gas leaving the intersection point experiences numerous secondary shocks that result in the rapid formation of a thick and marginally-bound disc. The mass distribution features two overdensities identified as spiral shocks that drive slow gas inflow along the mid-plane. Inward motion primarily takes place along the funnels of the newly-formed torus, from which a fraction of the matter can get accreted. Further out, the gas moves outward forming an extended envelope completely surrounding the accretion flow. Secondary shocks heat the debris at a rate of a few times $10^{44} \, \rm erg \, s^{-1}$ with a large fraction likely participating to the bolometric luminosity. These results pave the way towards a complete understanding of the early radiation from TDEs that progressively becomes accessible from observations.