ROSAT Hard-Spectrum X-Ray Source Catalog

ROSAT Hard-Spectrum X-Ray Source Catalog ROSATHARD ivo://nasa.heasarc/rosathard NASA/GSFC HEASARC Page et al. 2026-10-09 NASA/GSFC HEASARC help desk heasarc-vo at athena.gsfc.nasa.gov Survey Source This table contains a catalog of 147 serendipitous X-ray sources selected to have hard spectra (spectral indices Alpha < 0.5) from a survey of 188 ROSAT fields. Such sources must be the dominant contributors to the X-ray background at faint fluxes. The authors have used Monte Carlo simulations to verify that their technique is very efficient at selecting hard sources: the survey has >= 10 times as much effective area for hard sources as it has for soft sources above a 0.5 - 2 keV flux level of 10-14 erg cm-2 s-1. The distribution of best-fitting spectral slopes of the hard sources suggests that a typical ROSAT hard source in this survey has a spectral slope Alpha ~ 0. The hard sources have a steep number-flux relation (dN/dS ~ _S-Gamma, with a best-fitting value of Gamma = 2.72 +/- 0.12), and make up about 15% of all 0.5 - 2 keV sources with S > 10-14 erg cm-2 s-1. If their N(S) continues to fainter fluxes, the hard sources will comprise ~ 40% of sources with 5 x 10-15 < S < 10-14 erg cm-2 s-1. The population of hard sources can therefore account for the harder average spectra of ROSAT sources with S < 10-14erg cm-2 s-1. They probably make a strong contribution to the X-ray background at faint fluxes and could be the solution to the X-ray background spectral paradox. This table was created by the HEASARC in March 2012 based on <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/MNRAS/318/1073">CDS Catalog J/MNRAS/318/1073</a> file table2.dat, the ROSAT hard X-ray source catalog. This is a service provided by NASA HEASARC . 2000MNRAS.318.1073P https://heasarc.gsfc.nasa.gov/W3Browse/all/rosathard.html Catalog Research served-by HEASARC TAP https://heasarc.gsfc.nasa.gov/xamin/vo/cone?showoffsets&table=rosathard& GET text/xml 180 99999 true 73.99579167 -75.54141667 0.0166666666666667 https://heasarc.gsfc.nasa.gov/xamin/vo/tap https://heasarc.gsfc.nasa.gov/cgi-bin/W3Browse/getvotable.pl?name=rosathard GET text/xml https://heasarc.gsfc.nasa.gov/cgi-bin/W3Browse/w3query.pl?tablehead=name=heasarc_rosathard&Action=More+Options&Action=Parameter+Search&ConeAdd=1 ROSAT 0.0166666666666667 X-ray public rosathard ROSAT Hard-Spectrum X-Ray Source Catalog name Source Designation meta.id;meta.main char nullable seqid ROSAT Observation in Which Source Was Detected meta.id;obs.sequence char nullable ra Right Ascension degree pos.eq.ra;meta.main double nullable dec Declination degree pos.eq.dec;meta.main double nullable off_axis Off-Axis Angle of Source arcmin instr.offset double nullable sb_counts Number of Counts in PSPC Channels 11-41 (0.1-0.4keV) within the Source Circle ct phot;em.X-ray.soft short nullable mb_counts Number of Counts in PSPC Channels 52-90 (0.5-0.9keV] within the Source Circle ct phot;em.X-ray.soft short nullable hb_counts Number of Counts in PSPC Channels 91-201 (0.9-2.0 keV) within the Source Circle ct phot;em.X-ray.soft short nullable flux 0.5-2keV Flux erg/s/cm^2 phot.flux;em.X-ray.soft double nullable flux_pos_err Positive 68% Uncertainty in 0.5-2keV Flux (Upper Limit) erg/s/cm^2 stat.error;phot.flux;em.X-ray.soft double nullable flux_neg_err Negative 68% Uncertainty on 0.5-2keV Flux (Lower Limit) erg/s/cm^2 stat.error;phot.flux;em.X-ray.soft double nullable spectral_index Fitted Power-Law Spectral Slope spect.index;em.X-ray.soft double nullable snr PSS Significance of Source Above Background Level stat.snr;em.X-ray.soft double nullable error_radius Positional Uncertainty of Source from PSS arcsec stat.error;pos double nullable spectral_index_pos_err Positive 68% Uncertainty in Alpha (Upper Limit) stat.error;spect.index;em.X-ray.soft double nullable sb_bck_counts Expected Number of Background Counts in PSPC Channels 11-41 ct phot;instr.background;em.X-ray.soft double nullable optical_ctrprt_flag Flag [SI] Indicates Optical Counterpart Information meta.code;em.opt char nullable extraction_radius Source Circle Radius for Extraction of the Three-Color Spectrum arcsec phys.angSize short nullable spectral_index_neg_err Negative 68% Uncertainty in Alpha (Lower Limit) stat.error;spect.index;em.X-ray.soft double nullable psf_reduced_chi_squared Spread Function to the Source Radial Profile from Fit of the Model PSPC Point stat.fit.chi2;phys.angSize;src double nullable hb_bck_counts Expected Number of Background Counts in PSPC Channels 91-201 ct phot;instr.background;em.X-ray.soft double nullable exposure ROSAT PSPC Exposure Time After Good Time Screening s time.duration;obs.exposure double nullable mb_bck_counts Expected Number of Background Counts in PSPC Channels 52-90 ct phot;instr.background;em.X-ray.soft double nullable lii Galactic Longitude degree pos.galactic.lon double nullable bii Galactic Latitude degree pos.galactic.lat double nullable hard_spectral_prob Probability of Source Having Spectral Slope Alpha Less (Harder) Than 0.5 stat.probability;spect 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