The young active star AB Dor ( K1 IV-V ) has been observed 16 times in the last three years with the XMM-Newton and Chandra observatories , totalling 650 ks of high-resolution X-ray spectra .
The XMM/RGS observations with the highest and lowest average emission levels have been selected to study the coronal properties of AB Dor in two different activity levels .
We compare the results based on the XMM data with those obtained from a higher resolution Chandra/HETG spectrum , using the same line-based analysis technique .
We have reconstructed the plasma Emission Measure Distribution vs. temperature ( EMD ) in the range log T ( K ) \sim 6.1–7.6 , and we have determined the coronal abundances of AB Dor , obtaining consistent results between the two instruments .
The overall shape of the EMD is also consistent with the one previously inferred from EUVE data .
The EMD shows a steep increase up to the peak at log T ( K ) \sim 6.9 and a substantial amount of plasma in the range log T ( K ) \sim 6.9–7.3 .
The coronal abundances show a clear trend of increasing depletion with respect to solar photospheric values , for elements with increasing First Ionization Potential ( FIP ) , down to the Fe value ( [ Fe/H ] = –0.57 ) , followed by a more gradual recovery of the photospheric values for elements with higher FIP .
He-like triplets and Fe xxi 
and Fe xxii lines ratios indicate electron densities log n _ { e } \sim 10.8 cm ^ { -3 } at log T ( K ) \sim 6.3 and log n _ { e } \sim 12.5 cm ^ { -3 } at log T ( K ) \sim 7 , implying plasma pressures steeply increasing with temperature .
These results are interpreted in the framework of a corona composed of different families of magnetic loop structures , shorter than the stellar radius and in isobaric conditions , having pressures increasing with the maximum plasma temperature , and which occupy a small fraction ( f \sim 10 ^ { -4 } – 10 ^ { -6 } ) of the stellar surface .