Stellar transits across a magnetized accretion torus as a mechanism for plasmoid ejection

TL;DR

This study uses GRMHD simulations to explore how stellar passages near supermassive black holes can temporarily inhibit accretion and eject plasmoids, potentially observable through multi-messenger signals.

Contribution

It introduces the first detailed GRMHD simulation analysis of stellar-induced perturbations in black hole accretion flows, highlighting plasmoid ejection mechanisms.

Findings

Stellar passages can inhibit accretion temporarily.

Plasmoids are ejected along magnetic field lines.

Perturbations produce detectable variability signatures.

Abstract

The close neighbourhood of a supermassive black hole contains not only the accreting gas and dust but also stellar-sized objects, such as late-type and early-type stars and compact remnants that belong to the nuclear star cluster. When passing through the accretion flow, these objects perturb it by the direct action of stellar winds, as well as their magnetic and gravitational effects. By performing General-Relativistic Magnetohydrodynamic (GRMHD) simulations, we investigate how the passages of a star can influence the supermassive black hole gaseous environment. We focus on the changes in the accretion rate and the emergence of blobs of plasma in the funnel of an accretion torus. We compare results from 2D and 3D numerical computations that have been started with comparable initial conditions. We find that a quasi-stationary inflow can be temporarily inhibited by a transiting star, and the plasmoids can be ejected along the magnetic field lines near the rotation axis. We observe the characteristic signatures of the perturbing motion in the power spectrum of the accretion variability, which provides an avenue for a multi-messenger detection of these transient events. Finally, we discuss the connection of our results to multi-wavelength observations of galactic nuclei, with the emphasis on ten promising sources (Sgr~A*, OJ 287, J0849$+$5108, RE J1034$+$396, 1ES 1927+65, ESO 253--G003, GSN 069, RX J1301.9$+$2747, eRO-QPE1, eRO-QPE2).