( 2002. The American Astronomical Society. All rights reserved. Printed in U.S.A. EVIDENCE FOR ACCRETION: HIGH-RESOLUTION X-RAY SPECTROSCOPY OF THE CLASSICAL

We present high-resolution X-ray spectra of the X-rayÈbright classical T Tauri star, TW Hydrae, covering the wavelength range of 1.5È25 The dierential emission measure derived from Ñuxes ofA . temperature-sensitive emission lines shows a plasma with a sharply peaked temperature distribution, peaking at log T \ 6.5. Abundance anomalies are apparent, with iron very deÐcient relative to oxygen, while neon is enhanced relative to oxygen. Density-sensitive line ratios of Ne IX and O VII indicate den-sities near log A Ñare with rapid (D1 ks) rise time was detected during our 48 ks observation;n e \ 13. however, based on analysis of the emission-line spectrum during quiescent and Ñaring states, the derived plasma parameters do not seem strongly time-dependent. The inferred plasma temperature distribution and densities are consistent with a model in which the bulk of the X-ray emission from TW Hya is generated via mass accretion from its circumstellar disk. Assuming that accretion powers the X-ray emis-sion, our results for log suggest an accretion rate of D10~8 yr~1.n e