Radiative hydrodynamic models of accretion streams in Classical T Tauri Stars - Observatoire de Paris Access content directly
Conference Papers Year : 2018

Radiative hydrodynamic models of accretion streams in Classical T Tauri Stars

L. Ibgui
  • Function : Author
S. Orlando
  • Function : Author
R. Rodriguez
  • Function : Author
M. González
Sa L. De
  • Function : Author

Abstract

Classical T Tauri Stars (CTTSs) are young stars accreting mass from their circumstellar disk. According to the largely accepted magnetospheric accretion scenario, the disk extends up to the truncation radius. In this region, the magnetic field is strong enough to disrupt the inner part of the disk and to channel the material towards the star, thereby forming accretion columns. The material falls onto the star at free fall velocity and hits the stellar surface; this produces shocks that heat the plasma up to a few million degrees. In the last twenty years, the X-ray and UV observations of these systems have raised several questions. In particular, the value predicted by theoretical models is systematically above the observed X-ray luminosity, and, also, the UV lines arising from these regions show complex profiles, which cannot be easily interpreted with current accretion models based only on magnetohydrodynamical effects. To tackle these problems, we modelled the structure and the dynamics of the plasma in the impact region, using radiation hydrodynamics simulations that include, for the first time, the effects of radiative transport in the Non Local Thermodynamic Equilibrium (non-LTE) regime. We found that the radiation arising from the shocked plasma is partially absorbed by the unshocked accretion column. This might explain the excess of X-ray flux predicted by MHD models in which only radiative losses are considered. Moreover, due to the absorption of radiation, the pre-shock down-falling accreted material is gradually heated up to a few 10^5 K due to irradiation of X-rays arising from the shocked plasma at the impact region. We discuss the implication of this pre-shock heating for the UV and X-ray emission arising from the impact region.
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Dates and versions

obspm-03992813 , version 1 (16-02-2023)

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S. Colombo, L. Ibgui, S. Orlando, R. Rodriguez, M. González, et al.. Radiative hydrodynamic models of accretion streams in Classical T Tauri Stars. SF2A-2018: Proceedings of the Annual meeting of the French Society of Astronomy and Astrophysics, Jul 2018, Paris, France. pp.141 - 144. ⟨obspm-03992813⟩
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