Stellar Tidal Disruption Events in General Relativity

TL;DR

This paper reviews how general relativity influences tidal disruption events (TDEs) near supermassive black holes, highlighting observable signatures like rate cutoffs, accretion delays, and X-ray modulations.

Contribution

It introduces the theoretical predictions of relativistic effects on TDEs and discusses their potential observational signatures compared to Newtonian models.

Findings

Relativistic effects cause a cutoff in TDE rates for SMBHs above 10^8 M_sun.

Relativistic precession delays accretion disk formation and alters early light curves.

Quasi-periodic X-ray modulations may indicate disk and jet precession due to GR.

Abstract

A tidal disruption event (TDE) ensues when a star passes too close to the supermassive black hole (SMBH) in a galactic center and is ripped apart by the tidal field of the SMBH. The gaseous debris produced in a TDE can power a bright electromagnetic flare as it is accreted by the SMBH; so far, several dozen TDE candidates have been observed. For SMBHs with masses above $\sim 10^7 M_\odot$, the tidal disruption of solar-type stars occurs within ten gravitational radii of the SMBH, implying that general relativity (GR) is needed to describe gravity. Three promising signatures of GR in TDEs are: (1) a super-exponential cutoff in the volumetric TDE rate for SMBH masses above $\sim 10^8 M_\odot$ due to direct capture of tidal debris by the event horizon, (2) delays in accretion disk formation (and a consequent alteration of the early-time light curve) caused by the effects of relativistic precession on stream circularization, and (3) quasi-periodic modulation of X-ray emission due to global precession of misaligned accretion disks and the jets they launch. We review theoretical models and simulations of TDEs in Newtonian gravity, then describe how relativistic modifications give rise to these proposed observational signatures, as well as more speculative effects of GR. We conclude with a brief summary of TDE observations and the extent to which they show indications of these predicted relativistic signatures.