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 } \sim 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 ( \sim hours ) superhot flares accompanied by fluorescent Fe emission at 6.4 keV superimposed on a slowly-varying ( \sim 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 .