Open AccessOn equilibrium rotation of the central object of an accretion disc
Author(s) -
Glatzel Wolfgang,
Obach Carsten
Publication year - 1999
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.1365-8711.1999.02725.x
Subject(s) - physics , angular momentum , total angular momentum quantum number , accretion (finance) , rotation (mathematics) , angular momentum of light , classical mechanics , specific relative angular momentum , flux (metallurgy) , angular momentum coupling , astrophysics , torque , mechanics , quantum mechanics , geometry , mathematics , materials science , metallurgy
The hydrodynamic interaction of an accretion disc with its central object is reanalysed within the framework of the slim‐disc approximation. Arguments are presented against an interpretation of the total angular momentum flux as an eigenvalue of the system. A simple intuitive consideration is provided, which shows that the central object may be in a state of stationary rotation even if the disc imposes the constraint of a finite angular momentum flux into it. It is argued that equilibrium rotation is characterized by vanishing viscous torque rather than by zero total angular momentum flux. As a consequence, the central object can be in a state of stationary rotation below the break‐up limit, although its angular momentum increases. Despite accretion, even for positive total angular momentum flux and subcritical rotation, central objects are spun down within a considerable range of their parameters. The results are illustrated by application to FU Orionis systems.