XMM-Newton observations of the sigma Ori cluster. II. Spatial and spectral analysis of the.pdfVIP

Astronomy Astrophysics manuscript no. aa3605 February 4, 2008 (DOI: will be inserted by hand later) XMM-Newton observations of the σ Ori cluster. II. Spatial and spectral analysis of the full EPIC field ⋆ 1 1 2 E. Franciosini , R. Pallavicini , and J. Sanz-Forcada 1 INAF - Osservatorio Astronomico di Palermo, Piazza del Parlamento 1, I-90134 Palermo, Italy 5 2 Astrophysics Division – Research and Science Support Department of ESA, ESTEC, Postbus 299, NL-2200 AG Noordwijk, 0 The Netherlands 0 2 Received 9 June 2005/Accepted 15 September 2005 t c O Abstract. We present the results of an XMM-Newton observation of the young (∼ 2 − 4 Myr) cluster around the hot star σ Orionis. In a previous paper we presented the analysis of the RGS spectrum of the central hot star; here we discuss the 7 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 1 from the 2MASS catalogue. We find that late-type stars have a median log LX /Lbol ∼ −3.3, i.e. very close to the saturation v limit. We detected significant variability in ∼ 40% of late-type members or candidates, including 10 flaring sources; rotational 9 modulation is detected in one K-type star and possibly in another 3 or 4 stars. Spectral analysis of the brightest sources shows 0 typical quiescent temperatures in the range T1 ∼ 0.3 − 0.8 keV and T2 ∼ 1 −