- ID:
- ivo://nasa.heasarc/ngc2808xmm
- Title:
- NGC 2808 XMM-Newton X-Ray Point Source Catalog
- Short Name:
- NGC2808XMM
- Date:
- 07 Mar 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- Galactic globular clusters harbor binary systems that are detected as faint X-ray sources. These close binaries are thought to play an important role in the stability of the clusters by liberating energy and delaying the inevitable core collapse of globular clusters. The inventory of close binaries and their identification is therefore essential. This table contains some of the results, namely an X-ray source catalog, from XMM-Newton observations of the Galactic globular cluster NGC 2808. The authors use X-ray spectral and variability analysis combined with ultraviolet observations made with the XMM-Newton optical monitor and published data from the Hubble Space Telescope to identify sources associated with the clusters. They compare the results of their observations with estimates from population synthesis models. Five sources out of 96 X-ray sources detected above 4-sigma significance are likely to be related to NGC 2808. The authors find one quiescent neutron star low-mass X-ray binary candidate in the core of NGC 2808, and propose that the majority of the central sources in NGC 2808 are cataclysmic variables. An estimation leads to 20 +/- 10 cataclysmic variables with luminosity above 4.25 x 10<sup>31</sup> erg s<sup>-1</sup>. Millisecond pulsars could also be present in the core of NGC 2808, and some sources outside the half-mass radius could possibly be linked to the cluster. NGC 2808 was observed on February 1st 2005, for 41.8 kiloseconds (ks) with the three European Photon Imaging Cameras (EPIC MOS1, MOS2 and pn) on board the XMM-Newton observatory, in imaging mode, using a full frame window and a medium filter. This table was created by the HEASARC in February 2009 based on the electronic version of Table 2 from the paper which was obtained from the CDS (their catalog J/A+A/480/397 file table2.dat). This is a service provided by NASA HEASARC .
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- ID:
- ivo://nasa.heasarc/ngc2264xmm
- Title:
- NGC 2264 XMM-Newton X-Ray Point Source Catalog
- Short Name:
- NGC2264XMM
- Date:
- 07 Mar 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- This table contains (some of) the results from an X-ray imaging survey of the young cluster NGC 2264, carried out with the European Photon Imaging Cameras (EPIC) on board the XMM-Newton spacecraft. XMM-Newton EPIC observations were made separately of the northern and southern portions of NGC 2264 on 2001 March 20 and 2002 March 17 - 18, respectively. Details concerning the two pointings are summarized in Table 1 of the reference paper. The nominal integration time was 42 ks for both observations. The three EPIC cameras were operated in full window mode. To prevent contamination of the X-ray images by the XUV and EUV emission of the optically and UV-bright sources in the field of view, the thick filter was used, which imposes a strong cut-off in the response at the lower energies. The X-ray data are merged with extant optical and near-infrared photometry, spectral classifications, H-alpha emission strengths, and rotation periods to examine the interrelationships between coronal and chromospheric activity, rotation, stellar mass, and internal structure for a statistically significant sample of pre-main-sequence stars. Out of the 316 distinct point-like sources that were detected at >= 3-sigma levels in one or more of six EPIC images, a total of 300 distinct X-ray sources can be identified with optical or near-infrared counterparts. The sources are concentrated within three regions of the cluster: in the vicinity of S Mon, within the large emission/reflection nebulosity southwest of S Mon, and along the broad ridge of molecular gas that extends from the Cone Nebula to the NGC 2264 IRS 2 field. From the extinction-corrected color-magnitude diagram of the cluster, ages and masses for the optically identified X-ray sources are derived. A median age of ~ 2.5 Myr and an apparent age dispersion of ~ 5 Myr are suggested by pre-main-sequence evolutionary models. The X-ray luminosity of the detected sources appears well-correlated with bolometric luminosity, although there is considerable scatter in the relationship. Stellar mass contributes significantly to this dispersion, while isochronal age and rotation do not. X-ray luminosity and mass are well correlated such that L<sub>X</sub> ~ (M/M<sub>solar</sub>)<sup>1.5</sup>, which is similar to the relationship found within the younger Orion Nebula Cluster. No strong evidence is found for a correlation between E(H-K), the near-infrared color excess, and the fractional X-ray luminosity, which suggests that optically thick dust disks have little direct influence on the observed X-ray activity levels. Among the X-ray-detected weak-line T Tauri stars, the fractional X-ray luminosity, L<sub>X</sub>/L<sub>bol</sub>, is moderately well correlated with the fractional H-alpha luminosity, L<sub>H(alpha)</sub>/L<sub>bol</sub>, but only at the 2-sigma level of significance. The cumulative distribution functions for the X-ray luminosities of the X-ray-detected classical and weak-line T Tauri stars within the cluster are comparable, assuming the demarcation between the two classes is at an H-alpha equivalent width of 10 Angstroms. However, if the non-detections in X-rays for the entire sample of H-alpha emitters known within the cluster are taken into account, then the cumulative distribution functions of these two groups are clearly different, such that classical T Tauri stars are underdetected by at least a factor of 2 relative to the weak-line T Tauri stars. Examining a small subsample of X-ray-detected stars that are probable accretors based on the presence of strong H-alpha emission and near-infrared excess, the authors conclude that definitive non-accretors are ~ 1.6 times more X-ray luminous than their accreting counterparts. In agreement with earlier published findings for the Orion Nebula Cluster, the authors find a slight positive correlation (valid at the 2-sigma confidence level) between L<sub>X</sub>/L<sub>bol</sub> and the rotation period in NGC 2264 stars. The lack of a strong anti-correlation between X-ray activity and rotation period in the stellar population of NGC 2264 suggests that either the deeply convective T Tauri stars are rotationally saturated or that the physical mechanism responsible for generating magnetic fields in pre-main-sequence stars is distinct from the one that operates in evolved main-sequence stars. This table was created by the HEASARC in September 2007 based on the electronic version of Table 2 from the reference paper which was obtained from the electronic AJ site. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/ngc6530xmm
- Title:
- NGC 6530 XMM-Newton X-Ray Point Source Catalog
- Short Name:
- NGC6530XMM
- Date:
- 07 Mar 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- This table contains the results of a 20 ks XMM-Newton observation of the Lagoon Nebula (M 8). The EPIC images of this region reveal a cluster of point sources, most of which have optical counterparts inside the very young open cluster NGC 6530. The bulk of these X-ray sources are probably associated with low and intermediate mass pre-main sequence stars. One of the sources experienced a flare-like increase of its X-ray flux making it the second brightest source in M 8 after the O4 star 9 Sgr. The X-ray spectra of most of the brightest sources can be fitted with thermal plasma models with temperatures of kT ~ a few keV. Only a few of the X-ray selected PMS candidates are known to display H-alpha emission and were previously classified as classical T Tauri stars. This suggests that most of the X-ray emitting PMS stars in NGC 6530 are weak-line T Tauri stars. In addition to 9 Sgr, the EPIC field of view contains also a few early-type stars. This table contains information on 117 of the 119 X-ray sources (2 sources, a point source associated with 9 Sgr and an extended source associated with the Hourglass Nebula were excluded from this table by the authors) that were detected using the SAS source detection algorithms in the soft band (0.5 - 1.2 keV) of an EPIC observation of 9 Sgr which have either a combined likelihood >= 20 and are detected in the individual images from all 3 EPIC instruments with -ln p_i >= 3.0 or (in two cases) where clearly detected in 2 of the 3 instruments but fell outside of the FOV of the third. The faintest sources in this category have about 10-3 cts s<sup>-1</sup> over the 0.5 - 1.2 keV band of the MOS instruments. Assuming a 1 keV thermal spectrum with a neutral hydrogen column density of 0.17 x 10<sup>22</sup> cm<sup>-2</sup>, the faintest sources correspond to an observed flux of about 8.9 x 10<sup>-15</sup> erg cm<sup>-2</sup> s<sup>-1</sup> and an unabsorbed flux of 13.1 x 10<sup>-15</sup> erg cm<sup>-2</sup> s<sup>-1</sup> in the 0.5 - 5.0 keV energy range. Note that the corresponding observed flux in the 0.5 - 1.2 keV soft band would be 5.2 x 10<sup>-15</sup> erg cm<sup>-2</sup> s<sup>-1</sup>. 72 X-ray sources have a single optical counterpart from the Sung et al (2000, <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/AJ/120/333">CDS Cat. <J/AJ/120/333></a>) catalog or in the SIMBAD database within a radius of less than 9 arcsec. The average angular separation between the X-ray source and the optical counterpart is 4.1 +/- 2.1 arcseconds. 17 X-ray sources have two or more optical stars falling within the 9 arcsec radius. Seven of these sources have at least one known H-alpha emission star inside their error box. 28 sources do not have an optical counterpart in the catalogue of Sung et al. The authors have cross-correlated these sources with the Guide Star Catalog and, in most cases, they find one or several GSC objects inside the 9 arcsec radius. These optical counterparts are usually very faint (V or R >=17) except for sources 91, 92 and 94 that have counterparts with R magnitudes 15.0, 14.6 and 13.3 respectively (note that these sources fall outside the area investigated by Sung et al.). Sources 93, 96, 98, 99, 100, 101, 102 and 112 have no GSC counterpart. Most of the objects in Table 3 are therefore X-ray sources with high X-ray to visual luminosity ratios. Given the galactic coordinates of NGC 6530 (l_II = 6.14, b_II = -1.38), the total galactic column density along this line of sight must be extremely large and the number of extragalactic sources in the soft detection energy band should be extremely low. This table was created by the HEASARC in March 2007 based on <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/A+A/395/499">CDS catalog J/A+A/395/499</a> files table1.dat, table2.dat and table3.dat. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/ngc6231xmm
- Title:
- NGC 6231 XMM-Newton X-Ray Source Catalog
- Short Name:
- NGC6231XMM
- Date:
- 07 Mar 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- This table contains the results of an X-ray campaign towards the young open cluster NGC 6231. The XMM-Newton observations, of a total duration of ~ 180 ks, reveal that NGC 6231 is very rich in the X-ray domain too. Indeed, 610 X-ray sources were detected in the present field of view, centered on the colliding wind binary HD 152248 in the cluster core (RA, Dec J2000.0 of 16 54 10.06, -41 49 30.1). The limiting sensitivity of this survey is approximately 6 x 10^-15<sup>erg/s/cm</sup>2 but clearly depends on the location in the field of view and on the source spectrum. Using different existing catalogs, over 85% of the X-ray sources could be associated with at least one optical and/or infrared counterpart within a limited cross-correlation radius of 2.5 or 3-arcsec according to the optical/IR catalog used. The surface density distribution of the X-ray sources presents a slight N-S elongation. Once corrected for the spatial sensitivity variation of the EPIC instruments, the radial profile of the source surface density is well described by a King profile with a central density of about 8 sources per arcmin<sup>2</sup> and a core radius close to 3.1 arcminutes. The distribution of the X-ray sources seems closely related to the optical source distribution. The expected number of foreground and background sources should represent about 9% of the detected sources, thus strongly suggesting that most of the observed X-ray emitters are physically belonging to NGC 6231. Finally, beside a few bright but soft objects -- corresponding to the early-type stars of the cluster -- most of the sources are relatively faint (~5 x 10<sup>-15</sup> erg/s/cm<sup>2</sup>) with an energy distribution peaked around 1.0 - 2.0 keV. The catalog of the 610 X-ray sources detected in the 30'-diameter field of view of XMM-Newton is presented here, including the equatorial coordinates, logarithmic likelihoods and count rates for the three EPIC instruments and for various energy ranges, as well as the cross-identification of the X-ray sources with various optical/infrared catalogs (2MASS, GSC2.2, USNO B1.0, SSB06) and their most commonly used names (HD/HDE, CD, CPD, Segg., SBL98, Braes), with only the closest identifications being reported here. This table was created by the HEASARC in March 2007 based on <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/A+A/454/1047">CDS catalog J/A+A/454/1047</a> files table3.dat and table6.dat. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/napexmmcxo
- Title:
- NorthAmerica(NGC7000)&Pelican(IC5070)NebulaeX-RaySourceCatalog
- Short Name:
- NAPEXMMCXO
- Date:
- 07 Mar 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- This table contains some of the results from the first extensive X-ray study of the North-America and Pelican star-forming region (NGC 7000/IC 5070), with the aim of finding and characterizing the young population of this cloud. X-ray data from Chandra (four pointings) and XMM-Newton (seven pointings) were reduced and source detection algorithm applied to each image. The authors complement the X-ray data with optical and near-IR data from the IPHAS, UKIDSS, and 2MASS catalogs, and with other published optical and Spitzer IR data. More than 700 X-ray sources are detected, the majority of which have an optical or NIR counterpart. This allowed the authors to identify young stars in different stages of formation. Less than 30% of the X-ray sources are identified with a previously known young star. the authors argue that most X-ray sources with an optical or NIR counterpart, except perhaps for a few tens at near-zero reddening, are likely candidate members of the star-forming region, on the basis of both their optical and NIR magnitudes and colors, and of their X-ray properties such as spectral hardness or flux variations. They are characterized by a wide range of extinction, and sometimes near-IR excesses, both of which prevent derivation of accurate stellar parameters. The optical color-magnitude diagram suggests ages between 1-10 Myr. The X-ray members have a very complex spatial distribution with some degree of subclustering, qualitatively similar to that of previously known members. The detailed distribution of X-ray sources relative to the objects with IR excesses identified with Spitzer is sometimes suggestive of sequential star formation, especially near the 'Gulf of Mexico' region, probably triggered by the O5 star which illuminates the whole region. The authors confirm that around the O5 star no enhancement in the young star density is found, in agreement with previous results. Thanks to the precision and depth of the IPHAS and UKIDSS data used, the authors also determine the local optical-IR reddening law, and compute an updated reddening map of the entire region. This table contains the catalog of X-ray sources, with their optical and near-IR identifications, in the NGC 7000/IC 5070 (North America/Pelican) star formation complex. The final X-ray source list comprises 721 objects, of which there are 378 ACIS detections (of which 34 have an XMM-Newton counterpart), and 343 XMM-Newton-only detection. The chosen detection threshold, corresponding to approximately one spurious detection per field, ensures that no more than approximately ten of the 721 detections are spurious. The 11 XMM-Newton and Chandra fields analyzed in this study are listed in Tables 1 and 2, respectively, of the reference paper. This table was created by the HEASARC in July 2017 based on <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/A+A/602/A115">CDS Catalog J/A+A/602/A115</a> file table3.dat, the list of detected X-ray sources in the North America (NGC 7000) & Pelican Nebulae (IC 5070), and file table4.dat, the list of optical and near-IR photometric information for the counterparts of these X-ray sources. It does not contain table5.dat, the list of X-ray undetected stars that have IR or H-alpha excesses. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/omegcenxmm
- Title:
- Omega Centauri XMM-Newton X-Ray Point Source Catalog
- Short Name:
- OMEGCENXMM
- Date:
- 07 Mar 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- Omega Centauri (NGC 5139) is one of the best studied objects in our galaxy. It is the most massive globular cluster (5.1 x 10<sup>6</sup> solar masses), and is characterized by large core and half mass radii (154.88 and 250.8 arcseconds, respectively (Harris 1996, AJ, 112, 1487). The authors observed Omega Cen with XMM-Newton on August 13th, 2001. The observation lasted 37 ks and was performed with the medium filter. The authors detected 11 and 27 faint X-ray sources in the core and half mass radii, respectively, searching down to a luminosity of 1.3 x 10<sup>31</sup> ergs s<sup>-1</sup> in the 0.5 - 5 keV range (for an assumed distance to Omega Cen of 5.3 kpc). Most sources have bolometric X-ray luminosities between ~ 10<sup>31</sup> - 10<sup>32</sup> ergs s<sup>-1</sup>. The bulk of sources are hard and spectrally similar to CVs. The lack of soft faint sources might be related to the absence of millisecond pulsars in the cluster. The XMM-Newton observations reveal the presence of an excess of sources well outside the core of the cluster where several RS CVn binaries have already been found. The authors also analyzed a publicly available Chandra ACIS-I observation performed on January 24 - 25th, 2000, to improve the XMM-Newton source positions and to search for source intensity variations between the two data sets. 63 XMM-Newton sources have a Chandra counterpart, and 15 sources within the half-mass radius have shown time variability. Overall, the general properties of the faint X-ray sources in omega Cen suggest that they are predominantly CVs and active binaries (RS CVn or BY Dra). This table lists all 146 X-ray sources detected in the XMM-Newton observation above a maximum likelihood threshold in the 0.5 - 5 keV band of 12, including the 27 sources within the half-mass radius (listed in Table 1 of the reference paper), and the 119 sources outside the half-mass radius (listed in Table 2 of the reference paper). About 9 of the 27 sources within the half-mass radius are expected to be background sources, as are ~ 65 of the sources within 12.5 arcminutes of the cluster center, i.e., a significant fraction of the 146 total observed X-ray sources. For each XMM-Newton source, its position, count rate, correlation with previous X-ray observation, and their associated errors are given. The detailed spectral information given in Table 5 of the reference paper for 17 selected X-ray sources is however not included 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/400/521">CDS catalog J/A+A/400/521</a> files table1.dat, table2.dat and table3.dat. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/ros13hrxmm
- Title:
- ROSAT 13-hour Field XMM-Newton X-Ray Source Catalog
- Short Name:
- ROS13HRXMM
- Date:
- 07 Mar 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- This table contains the results of a deep X-ray survey conducted with XMM-Newton, centered on the UK ROSAT 13-hours deep field area. This region covers 0.18 square degrees, and is the first of the two areas covered with XMM-Newton as part of an extensive multi-wavelength survey designed to study the nature and evolution of the faint X-ray source population. This table contains the final catalog of 225 sources. Within the central 9 arcminutes, 68% of the source positions are accurate to 2 arcseconds, making optical follow-up relatively straightforward. The authors construct the N(>S) relation in four energy bands: 0.2-0.5, 0.5-2, 2-5 and 5-10 keV. In all but the highest energy band, they find that the source counts can be represented by a double power law with a bright-end slope consistent with the Euclidean case and a break around 10<sup>-14</sup> erg cm<sup>-2</sup> s<sup>-1</sup>. Below this flux, the counts exhibit a flattening. The 13-hours deep field is centered on the sky coordinates RA(J2000) = 13 34 37.1, Dec (J2000) = +37 53 02.2. The XMM-Newton observations were carried out in three separate revolutions during June 2001 for a total exposure time of 200ks. Approximately 40% of the total observation time was affected by high particle background flares, arising from soft protons hitting the detector. The data were therefore temporally filtered to remove these high-background periods. Filtering reduced the total useful exposure time from ~200 ks to ~120 ks. This table was created by the HEASARC in August 2007 based on <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/MNRAS/362/1371">CDS catalog J/MNRAS/362/1371</a> file table9.dat. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/spidersxmm
- Title:
- SDSS-IV/SPIDERS XMM-Based X-Ray Point Source Spectroscopic Catalog
- Short Name:
- SPIDERSXMM
- Date:
- 07 Mar 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- This catalog aims to provide a detailed description of the SPectroscopic IDentification of ERosita Sources (SPIDERS) survey, an SDSS-IV program aimed at obtaining spectroscopic classification and redshift measurements for complete samples of sufficiently bright X-ray sources. The authors describe the SPIDERS X-Ray Point Source Spectroscopic Catalog, considering its store of 11,092 observed spectra drawn from a parent sample of 14,759 ROSAT and XMM sources over an area of 5,129 deg<sup>2</sup> covered in SDSS-IV by the eBOSS survey. This catalog presents the SPIDERS XMM subsample of 3,196 sources which were drawn from the XMM Slew Survey source catalog, version 2 (XMMSL2), provided by the HEASARC in <a href="/W3Browse/xmm-newton/xmmslewful.html">XMMSLEWFUL</a>. The accompanying <a href="/W3Browse/rosat/spidersros.html">SPIDERSROS</a> table contains the 21,288 sources drawn from the Second ROSAT All-Sky Survey (2RXS) Source Catalog, available from the HEASARC as <a href="/W3Browse/rosat/rass2rxs.html">RASS2RXS</a>. This program represents the largest systematic spectroscopic observation of an X-ray selected sample. A total of 10,970 (98.9%) of the observed objects are classified and 10,849 (97.8%) have secure redshifts. The majority of the spectra (10,070 objects) are active galactic nuclei (AGN), 522 are cluster galaxies, and 294 are stars. The SDSS-IV/BOSS spectrographic observations are taken between 2014 and 2019. This table was created by the HEASARC in May 2020 based upon the <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/A+A/636/A97">CDS Catalog J/A+A/636/A97</a> file vcxmmsl2.dat. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/sa57xmm
- Title:
- Selected Area 57 XMM-Newton X-Ray Source Catalog
- Short Name:
- SA57XMM
- Date:
- 07 Mar 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- The maximum number density of Active Galactic Nuclei (AGNs), as deduced from X-ray studies, occurs at z >= 1, with lower luminosity objects peaking at smaller redshifts. Optical studies lead to a different evolutionary behaviour, with a number density peaking at z ~ 2 independently of the intrinsic luminosity, but this result is limited to active nuclei brighter than the host galaxy. A selection based on optical variability can detect low luminosity AGNs (LLAGNs), where the host galaxy light prevents the identification by non-stellar colours. The authors collected X-ray data in a field where there existed an optically-selected sample of "variable galaxies", i.e. variable objects with diffuse appearance, in order to investigate the X-ray and optical properties of the population of AGNs, particularly of low luminosity ones, where the host galaxy is visible. They observed a field of ~ 0.2 deg<sup>2</sup> in the Selected Area 57, for 67 ks with XMM-Newton. They correlated the list of detected X-ray sources with a photographic survey of SA 57, complete to B_J ~ 23 and with the available spectroscopic data. They obtained a catalog of 140 X-ray sources to limiting fluxes of 5 x 10<sup>-16</sup> and 2 x 10<sup>-15</sup> erg/cm<sup>2</sup>/s in the 0.5 - 2 keV and 2 - 10 keV bands, respectively, 98 of which are identified in the optical bands. The X-ray detection of part of the variability-selected candidates confirms their AGN nature. Diffuse variable objects populate the low luminosity side of the sample. Only 25/44 optically-selected QSOs are detected in X-rays. 15% of all QSOs in the field have X/O < 0.1. Additional information on the likely optical counterparts of 98 of the X-ray sources is available in the reference paper, e.g., in Table 3. This table was created by the HEASARC in September 2007 based on CDS table J/A+A/469/1211 file table2.dat. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/sigorixmm
- Title:
- Sigma Orionis Cluster XMM-Newton X-Ray Point Source Catalog
- Short Name:
- SIGORIXMM
- Date:
- 07 Mar 2025
- Publisher:
- NASA/GSFC HEASARC
- 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 .
