  We present a study of the X-ray sources present in the nearby L1551 star
forming region, based on a deep XMM observation complemented with Chandra data
for the brightest sources. All the known pre-main sequence stars in the region
have been detected, most of them with sufficient statistics to allow a detailed
study of the temporal and spectral characteristics of their X-ray emission.
Significant temporal (and spectral) variability on both short and long time
scales is visible for most of the stars. In particular XZ Tau shows
large-amplitude variations on time scales of several hours with large changes
in the intervening absorption, suggestive of the X-ray emission being eclipsed
by the accretion stream (and thus of the X-ray emission being partly or totally
accretion-induced). The coronal metal abundance of the WTTS sources is
clustered around Z = 0.2, while the CTTS sources span almost two orders of
magnitudes in coronal Z, even though the photospheric abundance of all stars in
the L1551 is likely to be very similar. Some individual elements (notably Ne)
appear to be systematically enhanced with respect to Fe in the WTTS stars. The
significant differences between the spectral and temporal characteristics of
the CTTS and WTTS populations suggest that a different emission mechanism is
(at least partly) responsible for the X-ray emission of the two types of stars.
