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

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 $e\le 0.99$ (compared to the more realistic case of parabolic orbits with $e=1$) on close orbits with impact parameter ${\hat{I}}^2\ge 3$. 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 $e\approx 0.6$ 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 $L_{\mathrm{bol}}\approx 3-5L_{\mathrm{Edd}}$ 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 $T_{\mathrm{rad}}\approx 3-5\times 10^5$ K may be visible for chance viewing angles. Our simulations predict that TDEs should be radiatively inefficient with $\hat{I}\cdot \approx 0.009-0.014$. These are the first simulations which simultaneously capture the stream, disk formation, and emitted radiation.

21 pages, 20 figures