Line and continuum radiative transfer modelling of AA Tau

Abstract

We present photometric and spectroscopic models of the Classical T Tauri star AA Tau. Photometric and spectroscopic variability present in observations of AA Tau is attributed to a magnetically induced warp in the accretion disc, periodically occulting the photosphere on an 8.2 d time-scale. Emission line profiles show signatures of both infall, attributed to magnetospherically accreting material, and outflow. Using the radiative transfer code TORUS, we have investigated the geometry and kinematics of AA Tau's circumstellar disc and outflow, which is modelled here as a disc wind. Photometric models have been used to constrain the aspect ratio of the disc, the offset angle of the magnetosphere dipole with respect to the stellar rotation axis, and the inner radius of the circumstellar disc. Spectroscopic models have been used to constrain the wind and magnetosphere temperatures, wind acceleration parameter, and mass-loss rate. We find that observations are best fitted by models with a mass accretion rate of 5 × 10-9 M⊙ yr-1, a dipole offset of between 10° and 20°, a magnetosphere that truncates the disc from 5.2 to 8.8R*, a mass-loss-rate to accretion-rate ratio of ∼0.1, a magnetosphere temperature of 8500-9000 K, and a disc-wind temperature of 8000 K. © 2014 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society.