  We studied the X-ray properties of the young (~1-8 Myr) open cluster around
the O8III star lambda Ori using XMM-Newton. We detected 167 X-ray sources, of
which 58 are identified with known cluster members, from massive stars down to
low-mass stars with spectral types M5.5. Another 23 sources were identified
with new possible photometric candidates. Late-type stars have a median log
LX/Lbol ~ -3.3, close to the saturation limit. Variability was observed in 35%
of late-type members, including six flaring sources. The emission from the
central hot star lambda Ori is dominated by plasma at 0.2-0.3 keV, with a
weaker component at 0.7 keV, consistently with a wind origin. The coronae of
late-type stars can be described by two plasma components with temperatures
T1~0.3-0.8 keV and T2~0.8-3 keV, and subsolar abundances Z~0.1-0.3 Zsun,
similar to what is found in other star-forming regions and associations. No
significant difference was observed between stars with and without
circumstellar discs, although the smallness of the sample of stars with discs
and accretion does not allow us to draw definitive conclusions. The X-ray
properties of lambda Ori late-type stars are comparable to those of the coeval
sigma Ori cluster, suggesting that stellar activity in lambda Ori has not been
significantly affected by the different ambient environment.
