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XMM-Newton Observations of the sigma Ori Cluster

XMM-Newton Observations of the sigma Ori Cluster

Publication date: 02 February 2006

Authors: Franciosini, E., et al.

Journal: Astronomy & Astrophysics
Volume: 446
Issue: 2
Page: 501
Year: 2006

Copyright: ESO

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 also 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 other 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_sol, similarly 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.

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