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We report a ~38 ks X-ray observation of McNeil's Nebula obtained with XMM on2004 April 4. V1647 Ori, the young star in outburst illuminating McNeil'sNebula, is detected with XMM and appears variable in X-rays. We investigate thehardness ratio variability and time variations of the event energy distributionwith quantile analysis, and show that the large increase of the count rate fromV1647 Ori observed during the second half of the observation is not associatedwith any large plasma temperature variations as for typical X-ray flares fromyoung low-mass stars. X-ray spectral fitting shows that the bulk (~75%) of theintrinsic X-ray emission in the 0.5-8 keV energy band comes from a soft plasmacomponent (0.9 keV) reminiscent of the X-ray spectrum of the classical T Tauristar TW Hya, for which X-ray emission is believed to be generated by anaccretion shock onto the photosphere of a low-mass star. The hard plasmacomponent (4.2 keV) contributes ~25% of the total X-ray emission, and can beunderstood only in the framework of plasma heating sustained by magneticreconnection events. We find a hydrogen column density of NH=4.1E22 cm-2, whichpoints out a significant excess of hydrogen column density compared to thevalue derived from optical/IR observations, consistent with the picture of therise of a wind/jet unveiled from ground optical spectroscopy. The X-ray fluxobserved with XMM ranges from roughly the flux observed by Chandra on 2004March 22 (~10 times greater than the pre-outburst X-ray flux) to a value twotimes greater than that caught by Chandra on 2004 March 7 (~200 times greaterthan the pre-outburst X-ray flux). We have investigated the possibility thatV1647 Ori displays a periodic variation in X-ray brightness as suggested by thecombined Chandra+XMM data set (abridged).Comment: 11 pages and 8 Figures. Accepted for publication by Astronomy &  Astrophysic

Enhanced X-ray variability from V1647 Ori, the young star in outburst illuminating McNeil's Nebula