Open AccessDisc outflows and the accretion rate gap
Author(s) -
Begelman Mitchell C.,
Celotti Annalisa
Publication year - 2004
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1111/j.1365-2966.2004.08137.x
Subject(s) - physics , astrophysics , accretion (finance) , active galactic nucleus , outflow , schwarzschild radius , astronomy , luminosity , adiabatic process , black hole (networking) , accretion disc , eddington luminosity , galaxy , meteorology , computer science , thermodynamics , link state routing protocol , computer network , routing protocol , routing (electronic design automation)
We argue that the observed ‘accretion rate gap’– between black holes in radio‐loud active galactic nuclei (AGN) accreting at close to the Eddington limit and those accreting at considerably lower rates – can be explained in terms of the adiabatic inflow–outflow scenario (ADIOS) for radiatively inefficient accretion. Whenever the accretion rate falls below a threshold value (corresponding to a luminosity L crit ) that depends on the viscosity parameter, α, the inner region of the accretion disc – extending from the marginally stable orbit to ∼1000 Schwarzschild radii – is susceptible to becoming hot and radiatively inefficient. If this happens, the disc luminosity decreases by a factor of ∼100, as most of the matter originally destined to be swallowed is instead expelled in a wind. According to our conjecture, accretion flows on to black holes never radiate steadily in the range ∼0.01 L crit < L < L crit , hence the inferred accretion rate gap. We expect the gap to exist also for black holes in X‐ray binaries, where it may be responsible for state transitions and the luminosity fluctuations associated with X‐ray nova outbursts.