X-ray emission from classical T Tauri stars: Accretion shocks and coronae?

Abstract

Context. Classical T Tauri stars (CTTS) are surrounded by actively accreting disks. According to current models material falls along the magnetic field lines from the disk with more or less free-fall velocity onto the star, where the plasma heats up and generates X-rays. Aims. We want to quantitatively explain the observed high energy emission and measure the infall parameters from the data. Absolute flux measurements allow to calculate the filling factor and the mass accretion rate. Methods. We use a numerical model of the hot accretion spot and solve the conservation equations. Results. A comparison to data from XMM-Newton and Chandra shows that our model reproduces the main features very well. It yields for TW Hya a filling factor of 0.3% and a mass accretion rate 2 × 10-10 M⊙ yr-1. © ESO 2007.