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We present the X-ray spectrum of TW Hya observed at high and intermediatespectral resolution with the Reflection Grating Spectrometer (RGS) and theEuropean Photon Imaging Camera (EPIC) onboard the XMM-Newton satellite. TW Hyais the first classical T Tauri star for which simultaneous X-ray data with bothhigh spectral resolution and high sensitivity were obtained, thus allowing toprobe the X-ray emission properties of stars in the early pre-main sequencephase. The high plasma density, the (comparatively) low temperature, andpeculiar chemical abundances in the X-ray emitting region on TW Hya areuntypical for stellar coronae. An alternative X-ray production mechanism istherefore called for and a natural explanation is an accretion column depletedof grain forming elements. The metal depletion could be either due to theoriginal molecular cloud that formed TW Hya or due to a settling of dust in thecircumstellar disk of TW Hya.

X-ray emission from a metal depleted accretion shock onto the classical T Tauri star TW Hya