Outbursts of Young Stellar Objects
arXiv:astro-ph/0310598 · doi:10.1111/j.1365-2966.2004.07288.x
Abstract
We argue that the outbursts of the FU Orionis stars occur on timescales which are much longer than expected from the standard disc instability model with α_{c} \gtrsim 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} \sim 40 \rsun. 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 on 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.
13 pages, 7 figures, accepted by MNRAS
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