Spectral properties of X-ray bright variable sources in the Taurus molecular cloud

Aims. We analyze 19 bright variable X-ray sources detected in the XMM-Newton Extended Survey of the Taurus Molecular Cloud (XEST), in order to characterize the variations with time of their coronal properties and to derive informations on the X-ray emitting structures. Methods. We performed time-resolved spectroscopy of the EPIC PN and MOS spectra of the XEST sources, using a model with one or two thermal components, and we used the time evolution of the temperatures and emission measures during the decay phase of ares to derive the size of the aring loops. Results. The light curves of the selected sources show di erent types of variability: ares, long-lasting decay or rise through the whole observation, slow modulation or complex are-lik e variability. Spectral analysis shows typical quiescent plasma temperatures of 5 n 10 MK and 15 n 35 MK; the cool component generally remains constant, while the observed ux changes are due to variations of the hot component. During ares the plasma reaches temperatures up to 100 MK and luminosities up to 10 31 erg s 1 . Loop sizes inferred from are analysis are generally smaller than or comparable to the stellar radius.