Quantifying the impact of relativistic precession on tidal disruption event light curves

Abstract

The tidal field of a black hole can turn a star into a gas stream whose orbit can precess, especially if the a black hole is rapidly spinning. In this work, we investigate the impact of precession on the light curves of tidal disruption events (TDE). To do so, we perform two-dimensional radiation-hydrodynamic simulations of the interaction of the TDE wind and luminosity with the precessed stream wrapped around the black hole. Our results show that in events with black holes of $\sim10^6~\text{M}_{\odot}$ and no orbit-spin inclination, the line of sight has little effect on the light curves, since the stream covers a small fraction of the solid angle as the precession is confined to the orbital plane. In the case of black holes of $\gtrsim10^7~\text{M}_{\odot}$ and high inclination ($i\sim90^{\circ}$), the light curve peaks can be delayed by $\sim$100 days due to presence of the precessed stream blocking the radiation in the early phase of the event. We also discuss our efforts to model self-consistently the hydrodynamic evolution of a tidal stellar stream on curved spacetimes by the presence of a massive black hole.

Figures (4)

• Figure 1: Initial conditions for the precessing TDE setup. Each panel shows a two-dimensional $(r,\theta)$ density maps for models with $a_\text{h}=0.9$ for inclination $i=90^{\circ}$ and black hole mass $M_\text{h}=10^{6.0}$, $10^{6.5}$, $10^{7.0}$, $10^{7.5}~\text{M}_{\odot}$. Spatial scales are shown in units of the Schwarzschild radius $R_\text{Sch}=2GM_{\rm h}/c^2$.
• Figure 2: Simulated light curves for models with $M_\text{h}=10^6$ (left-hand side) and $10^7$ M$_{\odot}$ (right-hand side). Each observer line of sight along $\theta_\text{obs}=0,~30^{\circ},~60^{\circ},~90^{\circ}$ is represented with solid yellow, dashed beige, dotted-dashed grey, and dotted blue lines, respectively. The solid thin black line is shown as a reference for an event without surrounding medium piro2020. The lower part of each panel shows the relative difference between the simulation and the reference.
• Figure 3: Stellar disruption evolution during pericentre passage from the simulation with SPHINCS. The panels correspond to density maps integrated along the $z$ axis that is perpendicular to the orbital plane. These maps were made using the code splash price2007. Notice that every panel does not show the same spatial scale.
• Figure 4: Mass fallback rate as a function of time from the first pericentre passage (solid blue line). The dashed gray line represents the $t^{-5/3}$ decay.