  We present results of pointed X-ray observations of the accreting jet-driving
T Tauri star RY Tau using Chandra and XMM-Newton. We obtained high-resolution
grating spectra and excellent-quality CCD spectra and light curves with the
objective of identifying the physical mechanisms underlying RY Tau's bright
X-ray emission. Grating spectra reveal numerous emission lines spanning a broad
range of temperature superimposed on a hot continuum. The X-ray emission
measure distribution is dominated by very hot plasma at T_hot ~ 50 MK but
higher temperatures were present during flares. A weaker cool plasma component
is also present as revealed by low-temperature lines such as O VIII. X-ray
light curves show complex variability consisting of short-duration (~hours)
superhot flares accompanied by fluorescent Fe emission at 6.4 keV superimposed
on a slowly-varying (~one day) component that may be tied to stellar rotation.
The hot flaring component is undoubtedly of magnetic (e.g. coronal) origin.
Soft and hard-band light curves undergo similar slow variability implying that
at least some of the cool plasma shares a common magnetic origin with the hot
plasma. Any contribution to the X-ray emission from cool shocked plasma is
small compared to the dominant hot component but production of individual
low-temperature lines such as O VIII in an accretion shock is not ruled out.
