Advection-dominated accretion and the black hole event horizon

2008/03/03 by Ramesh Narayan, Jeffrey E. McClintock · 24 citations
Engineering · Physics and Astronomy · #Accretion (finance) #Advection #Astronomy #Astrophysical Phenomena and Observations #Astrophysics #Black hole (networking) #Event (particle physics) #Event horizon #Galaxy #Gravitation #Heat Transfer Mechanisms #Neutron star #Physics #Stellar black hole #Strong gravity #astro-ph

paper · pdf · doi:10.1016/j.newar.2008.03.002

published as New Astron.Rev.51:733-751,2008 · To appear in "Jean-Pierre Lasota, X-ray binaries, accretion disks and compact stars" New Astronomy Reviews, eds. M.A. Abramowicz and O. Straub (Elsevier, 2008)

arxiv created 2008/03/03 · openalex publication_date 2008/03/19 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05

Abstract

As the luminosity of an accreting black hole drops to a few percent of Eddington, the spectrum switches from the familiar soft state to a hard state that is well-described by a distended and tenuous advection-dominated accretion flow (ADAF). An ADAF is a poor radiator, and the ion temperature can approach 10¹² K near the center, although the electrons are cooler, with their temperature typically capped at ~10^9-11 K. The foundational papers predicted that the large thermal energy in an ADAF would drive strong winds and jets, as later observed and also confirmed in computer simulations. Of chief interest, however, is the accreting gas that races inward. It carries the bulk of the accretion energy as stored thermal energy, which vanishes without a trace as the gas passes through the hole's event horizon. One thus expects black holes in the ADAF regime to be unusually faint. Indeed, this is confirmed by a comparison of accreting stellar-mass black holes and neutron stars, which reside in very similar transient X-ray binary systems. The black holes are on average observed to be fainter by a factor of ~100-1000. The natural explanation is that a neutron star must radiate the advected thermal energy from its surface, whereas a black hole can hide the energy behind its event horizon. The case for an event horizon in Sagittarius A*, which is immune to caveats on jet outflows and is furthermore independent of the ADAF model, is especially compelling. These two lines of evidence for event horizons are impervious to counterarguments that invoke strong gravity or exotic stars.

Citations

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Cited by

• Pre-outburstChandraobservations of the recurrent nova T Pyxidis
• SUZAKUBROADBAND SPECTROSCOPY OFSWIFTJ1753.5–0127 IN THE LOW-HARD STATE
• A systematic study of the condensation of the corona and the application for Γ 2-10 keV-Lbol/LEdd correlation in luminous active galactic nuclei
• On the convective instability of hot radiative accretion flows
• Black holes as gravitational atoms
• Active Galactic Nucleus Feedback with the Square Kilometre Array and Implications for Cluster Physics and Cosmology
• Study of MRI in stratified viscous plasma configuration
• General relativistic magnetohydrodynamic dynamo in thick accretion disks: fully nonlinear simulations
• Revised conditions for MRI due to isorotation theorem
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• Swift J1357.2−0933: the faintest black hole?
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• Parabolic Jets from the Spinning Black Hole in M87
• X-RAY AND RADIO VARIABILITY OF M31*, THE ANDROMEDA GALAXY NUCLEAR SUPERMASSIVE BLACK HOLE
• APPLICATION OF THE DISK EVAPORATION MODEL TO ACTIVE GALACTIC NUCLEI
• Outliers: multicolour photometry guiding the search for evolved binary systems in the globular cluster 47 Tucanae
• Iron Kα line of Kerr black holes with Proca hair

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