Magnetic Reconnection in Black-Hole Magnetospheres: Lepton Loading into Jets, Superluminal Radio Blobs, and Multi-wavelength Flares

Abstract

Supermassive black holes in active galactic nuclei launch relativistic jets, as indicated by observed superluminal radio blobs. The energy source of these jets is widely discussed in the theoretical framework of Blandford-Znajek process, the electromagnetic energy extraction from rotating black holes (BHs), while formation mechanism of the radio blobs in the electromagnetically-dominated jets has been a long-standing problem. Recent high-resolution magnetohydrodynamic simulations of magnetically arrested disks exhibited magnetic reconnection in a transient magnetically-dominated part of the equatorial disk near the BH horizon, which led to a promising scenario of efficient MeV gamma-ray production and subsequent electron-positron pair loading into BH magnetosphere. We develop this scenario to build a theoretical framework on energetics, timescales and particle number density of the superluminal radio blobs and discuss observable signatures in other wavebands. We analytically show that the non-thermal electrons emit broadband photons from optical to multi-MeV bands. The electron-positron pairs produced in the magnetosphere are optically thick for synchrotron-self absorption, so that the injected energy is stored in the plasma. The stored energy is enough to power the superluminal radio blobs observed in M87. This scenario predicts rather dim radio blobs around Sgr A*, which are consistent with no clear detection by current facilities. In addition, this scenario inevitably produces strong X-ray flares in a short timescale, which will be detectable by future X-ray satellites.

14 pages, 5 figures, 1 table, accepted for publication in ApJL

References in corpus (24)

• First M87 Event Horizon Telescope Results. I. The Shadow of the Supermassive Black Hole
• First Sagittarius A* Event Horizon Telescope Results. I. The Shadow of the Supermassive Black Hole in the Center of the Milky Way
• First M87 Event Horizon Telescope Results. VI. The Shadow and Mass of the Central Black Hole
• First M87 Event Horizon Telescope Results. V. Physical Origin of the Asymmetric Ring
• The Physics of Gamma-Ray Bursts and Relativistic Jets
• First Sagittarius A* Event Horizon Telescope Results. V. Testing Astrophysical Models of the Galactic Center Black Hole
• Formation of Hard Power-laws in the Energetic Particle Spectra Resulting from Relativistic Magnetic Reconnection
• Magnetic acceleration of ultra-relativistic jets in gamma-ray burst sources
• Variable TeV emission as a manifestation of jet formation in M87?
• Ab Initio Horizon-Scale Simulations of Magnetically Arrested Accretion in Sagittarius A* Fed by Stellar Winds
• Sgr A* near-infrared flares from reconnection events in a magnetically arrested disc
• State-of-the-art energetic and morphological modelling of the launching site of the M87 jet
• Black Hole Magnetospheres
• NuSTAR detection of high-energy X-ray emission and rapid variability from Sagittarius A* flares
• Recent Progress on Particle Acceleration and Reconnection Physics during Magnetic Reconnectionin the Magnetically-dominated Relativistic Regime
• Kinematics of the M87 jet in the collimation zone: gradual acceleration and velocity stratification
• Magnetization degree at the jet base of M87 derived from the event horizon telescope data: Testing magnetically driven jet paradigm
• A Resolution Study of Magnetically Arrested Disks
• Comptonization by Reconnection Plasmoids in Black Hole Coronae I: Magnetically Dominated Pair Plasma
• GRMHD Simulations and Modeling for Jet Formation and Acceleration Region in AGNs
• Pair Drizzle around Sub-Eddington Supermassive Black Holes
• The intrinsic structure of Sagittarius A* at 1.3 cm and 7 mm
• Matter density distribution of general relativistic highly magnetized jets driven by black holes
• Mushroom-instability-driven Magnetic Reconnections in Collisionless Relativistic Jets

Cited by in corpus (4)

• Observable signatures of stellar-mass black holes in active galactic nuclei
• A "coronal-mass-ejection'' model for flares in Sagittarius A*
• Discovery of Limb Brightening in the Parsec-scale Jet of NGC 315 through Global Very Long Baseline Interferometry Observations and Its Implications for Jet Models
• Nonuniform Particle Injection into Black Hole Jets by Radiative Magnetic Reconnection