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Keywords:

  • line: formation;
  • radiative transfer;
  • stars: formation;
  • stars: pre-main-sequence

ABSTRACT

We present 3D simulations of rotationally induced line variability arising from complex circumstellar environment of classical T Tauri stars (CTTS) using the results of the 3D magnetohydrodynamics (MHD) simulations of Romanova et al., who considered accretion on to a CTTS with a misaligned dipole magnetic axis with respect to the rotational axis. The density, velocity and temperature structures of the MHD simulations are mapped on to the radiative transfer grid, and corresponding line source function and the observed profiles of neutral hydrogen lines (Hβ, Paβ and Brγ) are computed using the Sobolev escape probability method. We study the dependency of line variability on inclination angles (i) and magnetic axis misalignment angles (Θ). We find the line profiles are relatively insensitive to the details of the temperature structure of accretion funnels, but are influenced more by the mean temperature of the flow and its geometry. By comparing our models with the Paβ profiles of 42 CTTS observed by Folha & Emerson, we find that models with a smaller misaligngment angle (Θ < ∼15°) are more consistent with the observations which show that majority of Paβ are rather symmetric around the line centre. For a high inclination system with a small dipole misalignment angle (Θ≈ 15°), only one accretion funnel (on the upper hemisphere) is visible to an observer at any given rotational phase. This can cause an anticorrelation of the line equivalent to the width in the blue wing (v < 0) and that in the red wing (v > 0) over half of a rotational period, and a positive correlation over the other half. We find a good overall agreement of the line variability behaviour predicted by our model and those from observations.