Ultra-Close Encounters of Stars With Massive Black Holes: Tidal Disruption Events With Prompt Hyperaccretion

TL;DR

This paper presents general relativistic simulations of ultra-close stellar encounters with intermediate mass black holes, revealing prompt disk formation and sustained super-Eddington accretion shortly after disruption.

Contribution

It introduces a new class of tidal disruption events with rapid disk formation and high accretion rates, differing from traditional models with delayed disk formation.

Findings

Prompt formation of thick accretion disks within hours.

Sustained super-Eddington accretion rates for several days.

Distinct observational signatures from ultra-close encounters.

Abstract

A bright flare from a galactic nucleus followed at late times by a $t^{-5/3}$ decay in luminosity is often considered the signature of the complete tidal disruption of a star by a massive black hole. The flare and power-law decay are produced when the stream of bound debris returns to the black hole, self-intersects, and eventually forms an accretion disk or torus. In the canonical scenario of a solar-type star disrupted by a $10^{6}\; M_\odot$ black hole, the time between the disruption of the star and the formation of the accretion torus could be years. We present fully general relativistic simulations of a new class of tidal disruption events involving ultra-close encounters of solar-type stars with intermediate mass black holes. In these encounters, a thick disk forms promptly after disruption, on timescales of hours. After a brief initial flare, the accretion rate remains steady and highly super-Eddington for a few days at $\sim 10^2\,M_\odot\,{\rm yr}^{-1}$.