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2011MNRAS.411..915R - Mon. Not. R. Astron. Soc., 411, 915-928 (2011/February-3)
Global 3D simulations of disc accretion on to the classical T Tauri star V2129 Oph.
ROMANOVA M.M., LONG M., LAMB F.K., KULKARNI A.K. and DONATI J.-F.
Abstract (from CDS):
Simulations show that if the disc is truncated at the distance of r≈ 6.2R{Ux2605} which is comparable with the corotation radius, rcor≈ 6.8 R{Ux2605}, then the high-latitude polar spot dominates, but the accretion rate obtained from the simulations (and from the accompanying theoretical calculations) is about an order of magnitude lower than the observed one. The accretion rate matches the observed one if the disc is disrupted much closer to the star, at 3.4R{Ux2605}. However, in that case the octupolar belt spots strongly dominate. In the intermediate case of r≈ 4.3R{Ux2605}, the polar spots are sufficiently bright, and the accretion rate is within the error bar of the observed accretion rate, and this model can explain the observations. However, an even better match has been obtained in experiments with a dipole field twice as strong compared with one suggested by Donati et al.
The torque on the star from the disc-magnetosphere interaction is small, and the time-scale of spin evolution, 2 {x} 107-6 {x} 108 yr is longer than the 2 {x} 106 yr age of V2129 Oph. This means that V2129 Oph probably lost most of its angular momentum in the early stages of its evolution, possibly, during the stage when it was fully convective, and had a stronger magnetic field. The propeller mechanism could also be responsible for the rapid spin-down.
The external magnetic flux of the star is strongly influenced by the disc: the field lines connecting the disc and the star inflate and form magnetic towers above and below the disc. The potential (vacuum) approximation is still valid inside the Alfvén (magnetospheric) surface where the magnetic stress dominates over the matter stress.
Abstract Copyright: 2010 The Authors. Journal compilation2010 RAS
Journal keyword(s): accretion, accretion discs - magnetic fields - MHD - stars: magnetic field
Simbad objects: 2
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