XMS ivo://nasa.heasarc/xms NASA/GSFC HEASARC Barcons et al. 2026-07-17 NASA/GSFC HEASARC help desk heasarc-vo at athena.gsfc.nasa.gov Survey Source X-ray sources at intermediate fluxes (a few x 10<sup>-14</sup> erg/cm<sup>2</sup>/s) with a sky density of ~ 100 deg<sup>2</sup> are responsible for a significant fraction of the cosmic X-ray background at various energies below 10 keV. The aim of this study is to provide an unbiased and quantitative description of the X-ray source population at these fluxes and in various X-ray energy bands. The XMM-Newton Medium sensitivity Survey (XMS) includes a total of 318 X-ray sources found among the serendipitous content of 25 XMM-Newton target fields. The XMS comprises four largely overlapping source samples selected at soft (0.5 - 2 keV), intermediate (0.5 - 4.5 keV), hard (2 - 10 keV) and ultra-hard (4.5 - 7.5 keV) bands, the first three of them being flux-limited. This study reports on the optical identification of the XMS samples, complete to 85 - 95%. At the flux levels sampled by the XMS, the authors find that the X-ray sky is largely dominated by Active Galactic Nuclei. The fraction of stars in soft X-ray selected samples is below 10%, and only a few per cent for hard X-ray selected samples. They find that the fraction of optically obscured objects in the AGN population stays constant at around 15-20% for soft and intermediate band selected X-ray sources, over 2 decades of flux. The fraction of obscured objects amongst the AGN population is larger (~ 35 - 45%) in the hard or ultra-hard selected samples, and constant across a similarly wide flux range. The distribution in X-ray-to-optical flux ratio is a strong function of the selection band, with a larger fraction of sources with high values in hard selected samples. Sources with X-ray-to-optical flux ratios in excess of 10 are dominated by obscured AGN, but with a significant contribution from unobscured AGN. This table was created by the HEASARC in March 2008 based on <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/A+A/476/1191">CDS catalog J/A+A/476/1191</a> files table2.dat and table5.dat. This is a service provided by NASA HEASARC . 2007A&A...476.1191B https://heasarc.gsfc.nasa.gov/W3Browse/all/xms.html Catalog Research served-by HEASARC TAP https://heasarc.gsfc.nasa.gov/xamin/vo/cone?showoffsets&table=xms& GET text/xml 180 99999 true 343.115 -18.03994444 0.0166666666666667 https://heasarc.gsfc.nasa.gov/xamin/vo/tap https://heasarc.gsfc.nasa.gov/cgi-bin/W3Browse/getvotable.pl?name=xms GET text/xml https://heasarc.gsfc.nasa.gov/cgi-bin/W3Browse/w3query.pl?tablehead=name=heasarc_xms&Action=More+Options&Action=Parameter+Search&ConeAdd=1 XMM-NEWTON 0.0166666666666667 X-ray public xms XMM-Newton Medium Sensitivity Survey (XMS) Source Catalog name Catalog Source Designation (XMS JHHMMSS.s+DDMMSS) 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 hb_flux Flux in Hard Band (2-10keV) (erg/s/cm^2) erg/s/cm^2 phot.flux;em.X-ray.medium double nullable hb_flux_error RMS Uncertainty for Hard Band Flux (erg/s/cm^2) erg/s/cm^2 stat.error;phot.flux;em.X-ray.medium double nullable gmag_limit Limit Flag for g-prime Magnitude meta.code;phot.mag;em.opt char nullable gmag g-prime Magnitude mag phot.mag;em.opt double nullable redshift Redshift src.redshift double nullable dec_optical_j2000 J2000 Declination of Optical Counterpart pos.eq.dec char nullable bii Galactic Latitude degree pos.galactic.lat double nullable sample_flags Flag [SHXU ] Indicates Sample meta.code char nullable sb_flux_error RMS Uncertainty for Soft Band Flux (erg/s/cm^2) erg/s/cm^2 stat.error;phot.flux;em.X-ray.soft double nullable sb_flux Flux in Soft Band (0.5-2keV) (erg/s/cm^2) erg/s/cm^2 phot.flux;em.X-ray.soft double nullable source_type Type of the Optical Counterpart src.class char nullable source_flag Flag [YCE] Indicates Identification of Source meta.code char nullable hardness_ratio_2_error RMS Uncertainty for HR2 stat.error;phot.flux;arith.ratio;em.X-ray double nullable imag i-prime Magnitude mag phot.mag;em.opt.I double nullable ib_flux Flux in Intermediate (X) Band (0.5-4.5keV) (erg/s/cm^2) erg/s/cm^2 phot.flux;em.X-ray double nullable rj_mag R Magnitude mag phot.mag;em.opt.R double nullable rmag r-prime Magnitude mag phot.mag;em.opt.R double nullable hardness_ratio_2 Hardness Ratio, HR2=(H-S)/(H+S) phot.flux;arith.ratio;em.X-ray double nullable ub_flux Flux in Ultra-Hard (U) Band (4.5-7.5keV) (erg/s/cm^2) erg/s/cm^2 phot.flux;em.X-ray.medium double nullable lii Galactic Longitude degree pos.galactic.lon double nullable imag_limit Limit Flag for i-prime Magnitude meta.code;phot.mag;em.opt.I char nullable ub_flux_error RMS Uncertainty for Ultra-Hard Band Flux (erg/s/cm^2) erg/s/cm^2 stat.error;phot.flux;em.X-ray.medium double nullable ib_flux_error RMS Uncertainty for Intermediate Band Flux (erg/s/cm^2) erg/s/cm^2 stat.error;phot.flux;em.X-ray double nullable class Browse Object Classification src.class short nullable rmag_limit Limit Flag for r-prime Magnitude meta.code;phot.mag;em.opt.R char nullable error_radius Position Error (arcsec) arcsec stat.error;pos double nullable ra_optical_j2000 J2000 Right Ascension of Optical Counterpart pos.eq.ra 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