Chan/Seren/Opt ivo://nasa.heasarc/chansexoid NASA/GSFC HEASARC Eckart et al. 2026-10-09 NASA/GSFC HEASARC help desk heasarc-vo at athena.gsfc.nasa.gov Optical Counterpart The Serendipitous Extragalactic X-ray Source Identification (SEXSI) Program is designed to expand significantly the sample of identified extragalactic hard X-ray sources at intermediate fluxes, 10<sup>-15</sup> ergs/cm<sup>2</sup>/s < 2-10 keV Flux <~ 10<sup>-13</sup> ergs/cm<sup>2</sup>/s. SEXSI, which includes sources derived from more than 2 square degrees of Chandra images, provides the largest hard X-ray-selected sample yet studied, offering an essential complement to the Chandra Deep Fields (total area of 0.2 square degrees). In Eckart et al. (2005, Paper II) R-band optical imaging of the SEXSI fields from the Palomar P60 and P200, the MDM 2.4m and 1.3m, and the Keck I telescopes is described. The authors have identified counterparts or derived flux limits for nearly 1000 hard X-ray sources. Using the optical images, they have derived accurate source positions. They have investigated correlations between optical and X-ray flux, and optical flux and X-ray hardness ratio. They have also studied the density of optical sources surrounding X-ray counterparts, as well as the properties of optically faint, hard X-ray sources. In Eckart et al. (2006, Paper III) optical spectra of 477 counterparts are presented. These spectra reach to R-band magnitudes of <~24 and have produced identifications and redshifts for 438 hard X-ray sources. Typical completeness levels in the 27 Chandra fields studied are 40-70%. The vast majority of the 2-10 keV selected sample are AGNs with redshifts between 0.1 and 3; the highest redshift source lies at z = 4.33. This table which combines data presented in Eckart et al. (2005, 2006) has links to the list of SEXSI X-ray sources (the HEASARC Browse table CHANSEXSI: see Paper I = Harrison et al. 2003, ApJ, 596, 944). This table was originally created by the HEASARC in June 2005 based on the CDS version of Table 3 from Eckart et al. (2005: CDS table J/ApJS/156/35/table3.dat). It was updated in August 2006 to include information from Table 2 of Eckart et al. (2006: the electronic version available at the electronic ApJ web site). This is a service provided by NASA HEASARC . 2006ApJS..165...19E https://heasarc.gsfc.nasa.gov/W3Browse/all/chansexoid.html Catalog Research served-by HEASARC TAP https://heasarc.gsfc.nasa.gov/xamin/vo/cone?showoffsets&table=chansexoid& GET text/xml 180 99999 true 193.20941667 -9.40458333 0.0166666666666667 https://heasarc.gsfc.nasa.gov/xamin/vo/tap https://heasarc.gsfc.nasa.gov/cgi-bin/W3Browse/getvotable.pl?name=chansexoid GET text/xml https://heasarc.gsfc.nasa.gov/cgi-bin/W3Browse/w3query.pl?tablehead=name=heasarc_chansexoid&Action=More+Options&Action=Parameter+Search&ConeAdd=1 CHANDRA 0.0166666666666667 Optical X-ray public chansexoid Chandra Serendipitous Extragalactic X-Ray Source ID (SEXSI) Opti name IAU-Registered Designation of X-Ray Source (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 redshift Redshift double nullable rc_mag The Cousins R Magnitude mag phot.mag;em.opt.R double nullable rc_mag_error Error on the Cousins R Magnitude mag stat.error;phot.mag;em.opt.R double nullable rc_mag_flag Flag Indicates Cousins R Magnitude Fainter Than Image Limit meta.code;phot.mag;em.opt.R short nullable log_fx_fopt Log of the Ratio of the X-Ray Flux to to the Optical Flux phot.flux;arith.ratio;em.X-ray;em.opt double 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 offset_total Total Position Difference of Optical Counterpart and X-Ray Source (arcsec) arcsec pos.angDistance;em.X-ray;em.opt double nullable lower_rf_wavelength Lower Spectrum Wavelength Range Angstrom int nullable stellarity SExtractor Stellarity Fraction src.class.starGalaxy double nullable hb_snr Signal-to-Noise Ratio of the Hard Detection stat.snr;em.X-ray.medium double nullable optical_id_flag Flag Indicates Information Concerning the Optical Identification meta.code;em.opt short nullable offset_ra Optical Counterpart Right Ascension Offset from X-Ray Right Ascension (arcsec) arcsec pos.angDistance;pos.eq.ra double nullable offset_dec Optical Counterpart Declination Offset from X-Ray Declination (arcsec) arcsec pos.angDistance;pos.eq.dec double nullable off_axis_angle Off-Axis Angle (arcmin) arcmin instr.offset double nullable log_nh_lower_flag Flag for Log_nH_Lower char nullable bii Galactic Latitude degree pos.galactic.lat double nullable log_nh Log of Best-Fit nH from Spectral Fit log(cm^-2) double nullable log_nh_lower One Sigma Low Value of Log_nH log(cm^-2) double nullable spectral_notes Flags Indicates Spectral Footnotes char nullable lii Galactic Longitude degree pos.galactic.lon double nullable hardness_ratio Hardness Ratio phot.count;arith.ratio;em.X-ray.medium double nullable log_nh_flag Flag for nH char nullable log_nh_upper One Sigma High Value of Log_nH log(cm^-2) double nullable log_lx Log of the hard-band (2.0 - 10 keV) Luminosity in erg/s log(erg/s) double nullable object_type Object Type char nullable upper_rf_wavelength Higher Spectrum Wavelength Range Angstrom int nullable cluster_flag Flag Indicates Source Potentially Within 1 Mpc of Known Target Cluster Center meta.code;src short nullable hardness_ratio_flag Flag Indicates Hardness Ratio Is Lower Limit meta.code;phot.count;arith.ratio;em.X-ray.medium short nullable image_limit_rc_mag Limiting Cousins R Magnitude of Image mag double nullable hb_flux Unabsorbed Hard Band (2.0-10keV) Flux (erg/cm^2/s) erg/s/cm^2 phot.flux;em.X-ray.medium double nullable log_nh_upper_flag Flag for Log_nH_Upper char nullable