The chromosphere and corona of T Tauri

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Abstract
Observations of the ultraviolet spectrum of the pre-main-sequence star T Tauri have been made using the International Ultraviolet Explorer (IUE) satellite. The fluxes of the emission lines are used to make models of the temperature and density structure of the chromosphere and transition region to the corona. Several models are discussed to cover the range of possible gas and electron pressures. Various spectroscopic techniques are used to limit the range of acceptable electron pressures. Previous observations in the X-ray flux measured with the Einstein satellite by Feigelson & De Campli are used to extend the models to a corona at Te ∼ 5 × 106 K. It is difficult to avoid the conclusion that a two-component atmosphere is required – one having a high electron pressure extending to high temperatures to produce the X-ray emission and the other a region of lower density where the mass loss, indicated by blueshifted absorption, originates. In addition to hydrostatic models a simple Alfvén wave driven, dynamic model is made using the same approximations as adopted by Hartmann et al. Other forms of heating functions remain to be explored.

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