Open AccessOutbursts of young stellar objects
Author(s) -
Matthews O. M.,
Speith R.,
Wynn G. A.
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.1365-2966.2004.07288.x
Subject(s) - physics , accretion (finance) , astrophysics , magnetic field , accretion disc , radius , stars , instability , stellar magnetic field , astronomy , mechanics , computer security , coronal mass ejection , quantum mechanics , computer science , solar wind
ABSTRACT We argue that the outbursts of the FU Orionis stars occur on time‐scales which are much longer than expected from the standard disc instability model with α c ≳ 10 −3 . The outburst, recurrence and rise times are consistent with the idea that the accretion disc in these objects is truncated at a radius R i ∼ 40 R ⊙ . In agreement with a number of previous authors, we suggest that the inner regions of the accretion discs in FU Ori objects are evacuated by the action of a magnetic propeller anchored to the central star. We develop an analytic solution for the steady‐state structure of an accretion disc in the presence of a central magnetic torque, and present numerical calculations to follow its time evolution. These calculations confirm that a recurrence time that is consistent with observations can be obtained by selecting appropriate values for viscosity and magnetic field strength.