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Description
This table contains some of the results of an analysis of the full EPIC field in an XMM-Newton observation of the young (~2 - 4 Myr) cluster around the hot star sigma Orionis. The authors 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. They detected eleven new possible candidate members from the 2MASS (<a href="https://cdsarc.cds.unistra.fr/ftp/cats/II/246">CDS Cat. <II/246></a>) catalog. The authors find that late-type stars have a median log L<sub>X</sub>/L<sub>bol</sub> ~ -3.3, i.e. very close to the saturation limit. They detected significant variability in ~ 40% of late-type members or candidates, including 10 flaring sources; rotational modulation was 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<sub>1</sub> ~ 0.3 - 0.8 keV and T<sub>2</sub> ~ 1 - 3 keV, with subsolar abundances Z ~ 0.1 - 0.3 solar, similar to what is found in other star-forming regions and associations. The authors 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. XMM-Newton observations of the sigma Ori cluster, centered on the hot star sigma Ori AB, were carried out as part of the Guaranteed Time of Roberto Pallavicini using both the EPIC MOS and PN cameras and the RGS instrument. The observation (ID 0101440301) started at 21:47 UT on March 23, 2002 and ended at 9:58 UT on March 24, 2002, for a total duration of 43 ks. The EPIC cameras were operated in Full Frame mode using the thick filter. This table contains the combined list of 88 X-ray sources positionally (<= 5") associated with confirmed or candidate cluster members, and 66 X-ray sources with no such positional associations, detected above a significance threshold of 5 sigma. The two X-ray sources (source numbers 67 and 167) with 2 possible positional associations are listed twice, once for each positional association, with the X-ray information repeated. Thus, there are 156 entries in this HEASARC table. This table was created by the HEASARC in May 2007 based on <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/A+A/446/501">CDS catalog J/A+A/446/501</a> files tablea1.dat and tableb.dat. This is a service provided by NASA HEASARC .
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