  We present the results of an XMM-Newton observation of the young (~2-4 Myr)
cluster around the hot star sigma Orionis. In a previous paper we presented the
analysis of the RGS spectrum of the central hot star; here we discuss the
results of the analysis of the full EPIC field. We have detected 175 X-ray
sources, 88 of which have been identified with cluster members, including very
low-mass stars down to the substellar limit. We detected eleven new possible
candidate members from the 2MASS catalogue. We find that late-type stars have a
median log L_X/L_bol ~ -3.3, i.e. very close to the saturation limit. We
detected significant variability in ~40% of late-type members or candidates,
including 10 flaring sources; rotational modulation is detected in one K-type
star and possibly in another 3 or 4 stars. Spectral analysis of the brightest
sources shows typical quiescent temperatures in the range T_1 ~ 0.3-0.8 keV and
T_2 ~ 1-3 keV, with subsolar abundances Z ~ 0.1-0.3 Z_sun, similar to what is
found in other star-forming regions and associations. We find no significant
difference in the spectral properties of classical and weak-lined T Tauri
stars, although classical T Tauri stars tend to be less X-ray luminous than
weak-lined T Tauri stars.
