Variations in emission from episodic plasmoid ejecta around black holes

• Published in: Monthly notices of the Royal Astronomical Society Vol. 454; no. 3; pp. 3283 - 3298
• Main Authors: Younsi, Ziri, Wu, Kinwah
• Format: Journal Article
• Language: English
• Published: London Oxford University Press 11.12.2015
• Subjects: Astrophysics; Black holes; Black holes (astronomy); Ejecta; Emission; Emission spectroscopy; Flares; Magnetic fields; Mathematical analysis; Plasmoids; Time dependence; X-ray astronomy; relativistic processes; black hole physics; Galaxy: centre; radiative transfer; gravitational lensing: strong; Sun: coronal mass ejections (CMEs)
• ISSN: 0035-8711; 1365-2966
• DOI: 10.1093/mnras/stv2203

The X-ray and radio flares observed in X-ray binaries and active galactic nuclei are attributed to energetic electrons in the plasma ejecta from the accretion flows near the black hole in these systems. It is argued that magnetic reconnection could occur in the coronae above the accretion disc around the black hole, and that this drives plasmoid outflows resembling the solar coronal mass ejection phenomenon. The X-ray and radio flares are emission from energetic electrons produced in the process. As the emission region is located near the black hole event horizon, the flare emission would be subject to special- and general-relativistic effects. We present calculations of the flaring emission from plasmoids orbiting around a black hole and plasmoid ejecta launched from the inner accretion disc when general-relativistic effects are crucial in determining the observed time-dependent properties of the emission. We consider fully general-relativistic radiative transfer calculations of the emission from evolving ejecta from black hole systems, with proper accounting for differential arrival times of photons emitted from the plasmoids, and determine the emission light curves of plasmoids when they are in orbit and when they break free from their magnetic confinement. The implications for interpreting time-dependent spectroscopic observations of flaring emission from accreting black holes are discussed.