  Using three XMM-Newton observations we study the X-ray emission of RU Lup, a
accreting and wind-driving CTTS. In comparison with other bright CTTS we study
possible signatures of accretion and winds in their X-ray emission. Results: We
find three levels of activity among the observations of RU Lup, clearly of
magnetic origin due to the corresponding high plasma temperatures. Density
analysis with the OVII triplet indicates high densities in the cool plasma,
suggesting accretion shocks to be a significant contributor to the soft X-ray
emission. No strong overall metal depletion is observed. Excess emission at 6.4
keV during the more active phase suggest the presence of iron fluorescence. In
accreting stars we find an excess of cool plasma as evidenced by lower
OVIII/OVII line ratios compared to main-sequence stars. High density plasma
appears to be only present in low-mass CTTS, while accreting stars with
intermediate masses (> 2 M_Sun) have lower densities. Conclusions: In all
investigated CTTS the characteristics of the cooler X-ray emitting plasma are
influenced by the accretion process. We suspect different accretion rates and
amount of funneling, possibly linked to stellar mass and radius, to be mainly
responsible for the different properties of their cool plasma component. The
exceptional strong X-ray absorption in RU Lup and other CTTS is probably
related to accretion flows and an optically transparent wind emanating from the
star or the disk.
