On the formation of Hα line emission around classical T Tauri stars

By R. Kurosawa, Tim Harries, Neil H. Symington University of Exeter, U. S. Andrews. 2006

160 citations recorded by the source corpus.

We present radiative transfer models of the circumstellar environment of classical T Tauri stars, concentrating on the formation of the Hα emission. The wide variety of line profiles seen in observations are indicative of both inflow and outflow , and we therefore employ a circumstellar structure that includes both magnetospheri c accretion and a disc wind. We perform systematic investigations of the model parameters for the wind and the magnetosphere to search for possible geometrical and physical conditions which lead to the types of profiles seen in observations. We find that the hybrid models can repro duce the wide range of profile types seen in observations, and that the most common profile t ypes observed occupy a large volume of parameter space. Conversely, the most infrequently observed profile morphologies require a very specific set of models parameters. We find our mo del profiles are consistent with the canonical value of the mass-loss rate to mass-accretion rate ratio (� = 0.1) found in earlier magneto-hydrodynamic calculations and observations, but the models with 0.05 < � < 0.2 are still in accord with observed Hα profiles. We investigate the wind contribution to the line profile as a function of model parameters, and examine the rel iability of Hα as a mass accretion diagnostic. Finally, we examine the Hα spectroscopic classification used by Reipurth et. al, and discuss the basic physical conditions that are re quired to reproduce the profiles in each classified type.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/4e01bf8cdc5da165c8f879b881a8a47c4f2e2e92

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In Astronomy and Astrophysics

1. J. Bouvier
2. G. Herczeg
3. L. Hillenbrand
4. A. Kulkarni
5. Suzanne Aigrain
6. S. Matt
7. R. Pudritz
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Citations in the corpus

• Magnetic fields and accretion flows on the classical T Tauri star V2129 Oph (2007, background): “Detailed radiative transfer computations (e.g., Symington et al. 2005b; Kurosawa et al. 2006) are needed to confirm this.”
• Magnetospheric accretion-ejection processes in the classical T Tauri star AA Tauri (2006, methodology): “The Hα average profile is reminiscent of the model Hα profile computed by Kurosawa et al. (2006) which assumes that the line is formed partly in an axisymmetric magnetospheric funnel flow and partly in a slowly accelerating disk wind both seen at a high inclination (see their Fig.”
• UV Excess Measures of Accretion onto Young Very Low Mass Stars and Brown Dwarfs (2008, methodology): “…in opticallythick post-shock gas, the Balmer continuum emission is produced in optically-thin pre-shock gas, and the Balmer line emission is mostly produced primarily in the magnetospheric accretion column (Hartmann et al. 1994; Calvet & Gullbring 1998; Muzerolle et al. 2001; Kurosawa et al. 2006).”
• Accretion-powered Stellar Winds. II. Numerical Solutions for Stellar Wind Torques (2008, background): “Furthermore, Kurosawa et al. (2006) modeled the Hα emission line in these systems and suggested that a stellar wind component could most naturally explain the profiles observed in ∼ 7% of the stars in a sample compiled by Reipurth et al. (1996).”
• Accretion to magnetized stars through the Rayleigh–Taylor instability: global 3D simulations (2008, background): “The spectral line profiles are dependent upon the density and velocity of the accretion flow (see, e.g., Symington et al. 2005; Kurosawa et al. 2006), and will therefore be affected by instabilities.”
• Accretion dynamics and disk evolution in NGC 2264: a study based on the Corot photometric observations (2010, methodology): “…⋆ The CoRoT space mission was developed and is operated by the French space agency CNES, with participation of ESA’s RSSD and Science Programmes, Austria, Belgium, Brazil, Germany, and Spain (Shu et al., 1994; Hartmann et al., 1994; Muzerolle et al., 2001; Kurosawa et al., 2006).”