Paper detail

Line formation in the inner winds of classical T Tauri stars: testing the conical-shell wind solution

We present the emission line profile models of hydrogen and helium based on the results from axisymmetric magnetohydrodynamics (MHD) simulations of the wind formed near the disk-magnetosphere boundary of classical T Tauri stars (CTTSs). We extend the previous outflow models of `the conical-shell wind' by Romanova et al. to include a well defined magnetospheric accretion funnel flow which is essential for modelling the optical and near-infrared hydrogen and helium lines of CTTSs. The MHD model with an intermediate mass-accretion rate shows outflows in conical-shell shape with a half opening angle about 35 degrees. The flow properties such as the maximum outflow speed in the conical-shell wind, maximum inflow speed in the accretion funnel, mass-accretion and mass-loss rates are comparable to those found in a typical CTTS. The density, velocity and modified temperature from the MHD simulations are used in a separate radiative transfer model to predict the line profiles and test the consistency of the MHD models with observations. The line profiles are computed with various combinations of X-ray luminosities, temperatures of X-ray emitting plasma, and inclination angles. A rich diversity of line profile morphology is found, and many of the model profiles are very similar to those found in observations. We find that the conical-shell wind may contribute to the emission in some hydrogen lines (e.g. H-alpha, H-beta, Pa-beta and Pa-gamma) significantly when the temperature in the wind is relatively high (e.g. \sim 10^{4} K); however, the wind contribution decreases rapidly when a lower wind temperature is adopted. The model well reproduces a relatively narrow and low-velocity blueshifted absorption component in He I (10830), which are often seen in observations.