Tom J. G. Wilson

S. Matt,
T.J. Harries



  • CTTSs are known for their hydrogen emission lines, magnetospheric accretion and mass outflow[1].

  • By comparing synthetic hydrogen profiles from the RT code TORUS[2] with observations of CTTSs, we aim to constrain and provide insight into the physics.

  • Our initial parameter study indicates that the existing line broadening mechanisms are insufficient to account for the observed hydrogen emission.

Stellar wind

Radiative Transfer Model

  • Synthetic line profile computed using the radiative transfer code TORUS.


  • The Figure shows line profiles for 29 T Tauri stars (columns) from the ESO Archive[3], selected to have an accretion rate range of 104. The stars are ordered by H⍺ peak intensity.

  • High resolution: R~1100 (infrared) and R~1800 (optical) spectra from VLT’s X-Shooter, observed in Jan 2010.

  • Near simultaneous observations of H⍺ (top), Paβ (middle), and Br𝛄 (bottom). The x-axis is velocity with a range of 600 to −600 kms-1.

  • A strong correlation of shape and intensity is seen between the infrared lines, but not between H⍺ and the infrared observations.
reipurth Class
FWHM vs. HW10%


  • The figure shows the FWHM vs. half width at 10% maxima (HW10%). The synthetic observations are clipped so that the H⍺ data points lie near the observed parameter space.

  • Synthetic and observed H⍺ lines show a good accord between the measured parameters of Reipurth classification[4], Wλ, FWHM, and HW10%.

  • Synthetic lines for Paβ and Br𝛄 are found to be too narrow and Stark broadening is unable to account for the difference. This suggests another form of broadening needs to be invoked.

  • Inverse P-Cygni profiles are commonly predicted by the simulations for Paβ and Br𝛄, yet this is not reflected in the observations[5].