Open AccessSlim accretion discs: a model for ADAF–SLE transitions
Author(s) -
Igumenshchev Igor V.,
Abramowicz Marek A.,
Novikov Igor D.
Publication year - 1998
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 - 10.1046/j.1365-8711.1998.01774.x
Subject(s) - physics , accretion (finance) , advection , transonic , radius , astrophysics , limiting , shock wave , shock (circulatory) , boundary value problem , mechanics , classical mechanics , thermodynamics , quantum mechanics , mechanical engineering , medicine , computer security , computer science , engineering , aerodynamics
We numerically construct slim, global, vertically integrated models of optically thin, transonic accretion discs around black holes, assuming a regularity condition at the sonic radius and boundary conditions at the outer radius of the disc and near the black hole. In agreement with several previous studies, we find two branches of shock‐free solutions, in which the cooling is dominated either by advection or by local radiation. We also confirm that the part of the accretion flow where advection dominates is in some circumstances limited in size: it does not extend beyond a certain outer limiting radius. New results found in our paper concern the location of the limiting radius and the properties of the flow near to it. In particular, we find that beyond the limiting radius the advective‐dominated solutions match on to Shapiro, Lightman &38; Eardley (SLE) discs through a smooth transition region. Therefore, the full global solutions are shock‐free and unlimited in size. There is no need to postulate an extra physical effect (e.g. evaporation) for triggering the ADAF–SLE transition. It occurs as a result of standard accretion processes described by the classic slim disc equations.