Evidence for Accretion: High-Resolution X-Ray Spectroscopy of the Classical T Tauri Star TW Hydrae

Joel H. Kastner, Rochester Institute of Technology
David P. Huenemoerder, Massachusetts Institute of Technology
Norbert S. Schulz, Massachusetts Institute of Technology
Claude R. Canizares, Massachusetts Institute of Technology
David A. Weintraub, Vanderbilt University

© 2002 The American Astronomical Society

The authors wish to thank Eric Feigelson, Andrea Dupree, and Steve Beckwith for incisive comments and enlightening discussions. This research was supported in part by contracts SV-61010 and NA-39073 to MIT.ISSN:1538-4365 Note: imported from RIT’s Digital Media Library running on DSpace to RIT Scholar Works in February 2014.


We present high resolution X-ray spectra of the X-ray bright classical T Tauri star, TW Hydrae, covering the wavelength range of 1.5-25 °A. The differential emission measure derived from fluxes of 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 deficient relative to oxygen, while neon is enhanced relative to oxygen. Density-sensitive line ratios of Ne ix and O vii indicate densities near (log ne)=13. A flare with rapid (~1 ks) rise time was detected during our 48 ksec observation; however, based on analysis of the emission-line spectrum during quiescent and flaring states, the derived plasma parameters do not appear 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 accretion powers the X-ray emission, our results for (log ne) suggest an accretion rate of ~10^−8M⊙ yr^−1 (Refer to PDF file for exact formulas).