SIGORIXMM ivo://nasa.heasarc/sigorixmm NASA/GSFC HEASARC Franciosini et al. 2026-10-09 NASA/GSFC HEASARC help desk heasarc-vo at athena.gsfc.nasa.gov Survey Source 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 . 2006A&A...446..501F https://heasarc.gsfc.nasa.gov/W3Browse/all/sigorixmm.html Catalog Research served-by HEASARC TAP https://heasarc.gsfc.nasa.gov/xamin/vo/cone?showoffsets&table=sigorixmm& GET text/xml 180 99999 true 84.72579167 -2.82483333 0.0166666666666667 https://heasarc.gsfc.nasa.gov/xamin/vo/tap https://heasarc.gsfc.nasa.gov/cgi-bin/W3Browse/getvotable.pl?name=sigorixmm GET text/xml https://heasarc.gsfc.nasa.gov/cgi-bin/W3Browse/w3query.pl?tablehead=name=heasarc_sigorixmm&Action=More+Options&Action=Parameter+Search&ConeAdd=1 XMM-NEWTON 0.0166666666666667 X-ray public sigorixmm Sigma Orionis Cluster XMM-Newton X-Ray Point Source Catalog name Catalog Source Designation meta.id;meta.main char nullable ra Right Ascension degree pos.eq.ra;meta.main double nullable dec Declination degree pos.eq.dec;meta.main double nullable count_rate Count Rate in the 0.3-7.8 keV Band ct/s phot.count;em.X-ray double nullable count_rate_error RMS Uncertainty on Count Rate ct/s stat.error;phot.count;em.X-ray double nullable optical_name Designation of Optical Counterpart meta.id.assoc char nullable imag I Magnitude mag phot.mag;em.opt.I double nullable spect_type MK Spectral Type src.spType char nullable snr Significance of Detection stat.snr;em.X-ray double nullable optical_name_flag Flag [cde] Indicates Note on Optical Counterpart meta.code char nullable lii Galactic Longitude degree pos.galactic.lon double nullable source_number Sequential Identification Number for Each X-Ray Source in Catalog meta.id short nullable ri_color R-I Color Index mag phot.color;em.opt.R;em.opt.I double nullable bii Galactic Latitude degree pos.galactic.lat double nullable ij_color I-J color Index mag phot.color;em.opt.I;em.IR.J double nullable log_lx Logarithm of the Unabsorbed X-Ray Luminosity in 0.3-8 keV Band log(erg/s) phys.luminosity;em.X-ray double nullable source_flag Flag [YN] Indicates X-Ray Source Detected Only on One MOS meta.code char nullable class Browse Object Classification src.class short nullable cluster_flag Flag [YN] Indicates Source Table meta.code char nullable log_lx_flag Flag [F] Indicates X-Ray Luminosity Derived from PN or MOS1 Spectral Fits meta.code char nullable spect_type_flag Flag [L] Indicates Spectral Type Taken from Literature meta.bib char nullable ttau_flag Flag Indicates Probable/Possible Classical or Weak-Lined T Tauri Star meta.code char nullable "__x_ra_dec" System unit vector column double nullable "__y_ra_dec" System unit vector column double nullable "__z_ra_dec" System unit vector column double nullable "__row" System index column char nullable off_set Offset Between X-Ray and Optical Source Positions (arcsec) arcsec pos.angDistance;em.opt;em.X-ray double nullable