FU Orionis objects ( FUors ) have undergone strong optical outbursts and are thought to be young low-mass stars accreting at high rates of up to \dot { M } _ { acc } \sim 10 ^ { -4 } M _ { \odot } yr ^ { -1 } .
FUors have been extensively studied at optical and infrared wavelengths , but little is known about their X-ray properties .
We have thus initiated a program aimed at searching for and characterizing their X-ray emission .
First results are presented here for the prototype star FU Orionis based on observations obtained with XMM-Newton .
Its CCD X-ray spectrum is unusual compared to those of accreting classical T Tauri stars ( cTTS ) .
The cool and hot plasma components typically detected in cTTS are present but are seen through different absorption column densities .
The absorption of the cool component is consistent with A _ { V } \approx 2.4 mag anticipated from optical studies but the absorption of the hot component is at least ten times larger .
The origin of the excess absorption is uncertain but cold accreting gas or a strong near-neutral wind are likely candidates .
The hot plasma component accounts for most of the observed X-ray flux and thermal models give very high temperatures kT \geq 5 keV .
The most prominent feature in the X-ray spectrum is an exceptionally strong Fe K emission line at 6.67 keV and weak emission from fluorescent Fe I at \approx 6.4 keV may also be present .
The high plasma temperature clearly demonstrates that the emission is dominated by magnetic processes .
We discuss possible origins of the unusual X-ray spectrum in the context of a complex physical environment that likely includes disk accretion , a strong wind , magnetic activity , and close binarity .