Modeling accretion shocks on CTTSs and their X-ray emission

Abstract

Recent high spectral resolution X-ray observations of some CTTSs show the presence of high density plasma (ne=10^{11}-10^{13} cm^{-3}) at temperature T=2-3 MK. This plasma is likely heated up by an accretion shock on the star surface. We investigate this issue by an accurate modelling of the impact of an accretion stream onto the stellar chromosphere. Specifically, we present a large set of 1D hydrodynamical simulations aimed at investigating the physical properties of the system as a function of the density, and the velocity of the accretion stream and of the abundances of the heavy elements. We also synthesize the plasma X-ray emission from the simulations results, in order to link the observed properties of the CTTSs with the accretion shock physics. Furthermore, we present results of 2D magneto-hydrodynamical simulations aimed at investigating the role of the magnetic field in confining the shocked plasma at the base of the accretion column for different magnetic field strength.