Global Simulations of Tidal Disruption Event Disk Formation via Stream Injection in GRRMHD

TL;DR

This study uses advanced GRRMHD simulations to explore early accretion disk formation from tidal disruption events, revealing insights into disk eccentricity, radiation, and observational signatures.

Contribution

First simulations to simultaneously model stream injection, disk formation, and emitted radiation in TDEs, providing new understanding of their dynamics and observational features.

Findings

Disks become mildly circularized with eccentricity ~0.6 within days.

TDE radiation is mildly super-Eddington with luminosity 3-5 times Eddington.

Photosphere is highly asymmetric, affecting viewing angle-dependent observations.

Abstract

We use the general relativistic radiation magnetohydrodynamics code \verb=KORAL= to simulate the early stages of accretion disk formation resulting from the tidal disruption of a solar mass star around a super massive black hole (BH) of mass $10^6\,M_\odot$. We simulate the disruption of artificially more bound stars with orbital eccentricity $e\leq0.99$ (compared to the more realistic case of parabolic orbits with $e=1$) on close orbits with impact parameter $\beta\geq3$. We use a novel method of injecting the tidal stream into the domain. For two simulations, we choose $e=0.99$ and inject mass at a rate that is similar to realistic TDEs. We find that the disk only becomes mildly circularized with eccentricity $e\approx0.6$ within the $3.5$ days that we simulate. The rate of circularization is faster for pericenter radii that come closer to the BH. The emitted radiation is mildly super-Eddington with $L_{\rm{bol}}\approx3-5\,L_{\rm{Edd}}$ and the photosphere is highly asymmetric with the photosphere being significantly closer to the inner accretion disk for viewing angles near pericenter. We find that soft X-ray radiation with $T_{\rm{rad}} \approx 3-5\times 10^5$ K may be visible for chance viewing angles. Our simulations predict that TDEs should be radiatively inefficient with $\eta\approx0.009-0.014$. These are the first simulations which simultaneously capture the stream, disk formation, and emitted radiation.