Electron-Positron Pairs in Hot Accretion Flows and Thin Disk Coronae

Abstract

We investigate equilibrium accretion flows dominated by $e^{+}{e}^{-}$ pairs. We consider one- and two-temperature accretion disk coronae above a thin disk, as well as hot optically thin two-temperature accretion flows without an underlying thin disk; we model the latter in the framework of advection-dominated accretion flows (ADAFs). In all three cases we include equipartition magnetic fields. We confirm the previous result that the equilibrium density of pairs in two-temperature ADAFs is negligible; and show that the inclusion of magnetic fields and the corresponding synchrotron cooling reduces the pair density even further. Similarly, we find that pairs are unimportant in two-temperature coronae. Even when the corona has significantly enhanced heating by direct transfer of viscous dissipation in the thin disk to the corona, the inefficient Coulomb coupling between protons and electrons acts as a bottleneck and prevents the high compactness required for pair-dominated solutions. Only in the case of a one-temperature corona model do we find pair-dominated thermal equilibria. These pair-dominated solutions occur over a limited range of optical depth and temperature.

38 pages, including 10 figures, LaTeX; to appear in ApJ

References in corpus (5)

• Particle Heating by Alfvenic Turbulence in Hot Accretion Flows
• Radiative Efficiency of Collisionless Accretion
• Cyclo-synchrotron emission from magnetically dominated active regions above accretion discs
• Two-temperature coronae in active galactic nuclei
• Magnetic Flares and the Observed Optical Depth in Seyfert Galaxies

Cited by in corpus (7)

• Hot Accretion Flows Around Black Holes
• Pair Production in Low Luminosity Galactic Nuclei
• Preheated Advection Dominated Accretion Flow
• General-relativistic model of hot accretion flows with global Compton cooling
• Two temperature solutions and emergent spectra from relativistic accretion discs around black holes
• A model for electromagnetic extraction of rotational energy and formation of accretion-powered jets in radio galaxies
• Influences of magnetic coupling process on the spectrum of a disk covered by the corona