Modeling the Hα line emission around classical T Tauri stars using magnetospheric accretion and disk wind models
Departamento de Física, ICEx-UFMG
CP 702, Belo Horizonte,
2 Department of Astronomy, University of Michigan, 830 Dennison Building, 500 Church Street, Ann Arbor, MI 40109, USA
3 Space Telescope Science Institute, 3700 San Martin Dr., Baltimore, MD 21218, USA
Accepted: 20 July 2010
Context. Spectral observations of classical T Tauri stars show a wide range of line profiles, many of which reveal signs of matter inflow and outflow. Hα is the most commonly observed line profile owing to its intensity, and it is highly dependent on the characteristics of the surrounding environment of these stars.
Aims. Our aim is to analyze how the Hα line profile is affected by the various parameters of our model, which contains both the magnetospheric and disk wind contributions to the Hα flux.
Methods. We used a dipolar axisymmetric stellar magnetic field to model the stellar magnetosphere, and a modified Blandford & Payne model was used in our disk wind region. A three-level atom with continuum was used to calculate the required hydrogen level populations. We used the Sobolev approximation and a ray-by-ray method to calculate the integrated line profile. Through an extensive study of the model parameter space, we investigated the contribution of many of the model parameters to the calculated line profiles.
Results. Our results show that the Hα line is strongly dependent on the densities and temperatures inside the magnetosphere and the disk wind region. The bulk of the flux comes most of the time from the magnetospheric component for standard classical T Tauri star parameters, but the disk wind contribution becomes more important as the mass accretion rate, the temperatures, and the densities inside the disk wind increase. We also found that most of the disk wind contribution to the Hα line is emitted at the innermost region of the disk wind.
Conclusions. Models that take into consideration both inflow and outflow of matter are a necessity to fully understand and describe classical T Tauri stars.
Key words: accretion, accretion disks / line: profiles / magnetohydrodynamics (MHD) / radiative transfer / stars: formation / stars: pre-main sequence
© ESO, 2010