J/MNRAS/318/1073ivo://CDS.VizieR/J/MNRAS/318/1073doi:10.26093/cds/vizier.73181073CDSPage M.J.Mittaz J.P.D.Carrera F.J.2024-06-27T07:10:41Z2008-04-23T22:40:08ZCDS support team

CDS, Observatoire de Strasbourg, 11 rue de l'Universite, F-67000 Strasbourg, France

cds-question@unistra.frWe present a catalogue of 147 serendipitous X-ray sources selected to have hard spectra ({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. We have used Monte Carlo simulations to verify that our 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 0.5-2keV flux level of 10^-14^erg/cm^2^/s. The distribution of best-fitting spectral slopes of the hard sources suggests that a typical ROSAT hard source in our survey has a spectral slope {alpha}~0. The hard sources have a steep number flux relation (dN/dS_{mu}_S^-{gamma}^ with a best-fitting value of {gamma}=2.72+/-0.12) and make up about 15 per cent of all 0.5-2keV sources with S>10^-14^erg/cm^2^/s. If their N(S) continues to fainter fluxes, the hard sources will comprise ~40 per cent of sources with 5x10^-15^<S<10^-14^erg/cm^2^/s. The population of hard sources can therefore account for the harder average spectra of ROSAT sources with S<10^-14^erg/cm^2^/s. 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.2000MNRAS.318.1073Phttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/MNRAS/318/1073CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toIX/30 : Second ROSAT PSPC Catalog (ROSAT, 2000)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/MNRAS/318/1073https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/MNRAS/318/1073http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/MNRAS/318/1073https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/MNRAS/318/1073https://vizier.iucaa.in/viz-bin/votable?-source=J/MNRAS/318/1073http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/MNRAS/318/1073GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/MNRAS/318/1073/table2 (Hard source catalogue)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/MNRAS/318/1073/table2?https://vizier.iucaa.in/viz-bin/conesearch/J/MNRAS/318/1073/table2?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/MNRAS/318/1073/table2?GETtext/xml+votable180.050000true1.0718333-25.98752780.0055555555555555566/597 2186 2220 2227 4303 4324 4403 4831 5063 5255 5414 5417 5420 5689 5804 5855 5975 6026 6038 6048 6050-6051 6057 6059 6062 7273 7391 7642 7959 7988 8845 9146 10039 10169 10386-10387 10422 10856 10912 10979 11029 11203 11206 11434 11596 11730 11791 11802 12122 13333 16403 16589 16701 17778 19283 19802 19886 19935 20061 20179 20618 22721 25585 26022 26125 26561 26563 26650 26902 27133 27552 28184 28356 28396 28471 28517 28562 28581 33034 33193 33635 33716 33756 33986 34097 34361-34363 34463 34905 35759 35770 36129 36132 36247 36523 36526 36547 44993 46740 47047 47058 48162-48163https://cdsarc.cds.unistra.fr/viz-bin/moc/J/MNRAS/318/1073?format=asciiX-raydefaultJ/MNRAS/318/1073/table2Hard source cataloguerecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintRXJSource name based on J2000 coordinates of ROSAT source from PSS (1)meta.id;meta.maincharRORROSAT observation in which source was detectedobs.param;obscharExpTimeROSAT PSPC exposure time after good time screeningkstime.duration;obs.exposurefloatOffAxisOff-axis angle of sourcearcmininstr.offsetfloatePosPositional uncertainty of source from PSSarcsecstat.errorfloatsigmaPSS significance of source above background levelstat.fit.goodnessfloatPSFSpread function to the source radial profile in 5" bins out to 1', from a fit of the model PSPC pointspect.dopplerVelocfloatRadSource circle radius for extraction of the three-colour spectrumarcsecstat.fit.paramintC1Number of counts in PSPC channels 11-41 (0.1-0.4keV) within the source circlectphot.count;em.X-rayintC2Number of counts in PSPC channels 52-90 (0.5-0.9keV] within the source circlectphot.count;em.X-rayintC3Number of counts in PSPC channels 91-201 (0.9-2.0 keV) within the source circlectphot.count;em.X-rayintB1Expected number of background counts in PSPC channels 11-41 within the source circlectmeta.numberfloatB2Expected number of background counts in PSPC channels 52-90 within the source circlectmeta.numberfloatB3Expected number of background counts in PSPC channels 91-201 within the source circlectmeta.numberfloatalphaFitted power-law spectral slopespect.indexfloatE_alpha68% uncertainty in alpha (upper limit)stat.error;stat.maxfloate_alpha68% uncertainty in alpha (lower limit)stat.error;pos.eq.rafloatProbProbability of source having spectral slope alpha<(harder than) 0.5arith.grad;pos.eq.rafloatS0.5-20.5-2keV flux (3)1e-17W.m**-2phot.flux;em.X-rayfloatE_S0.5-268% uncertainty on S0.5-2 (upper limit) (3)1e-17W.m**-2stat.error;stat.maxfloate_S0.5-268% uncertainty on S0.5-2 (lower limit) (3)1e-17W.m**-2stat.errorfloatFlag[SI] Optical counterpart flag (2)meta.code.errorchar2RXPDisplay the PSPC data (2RXP, Cat. IX/30)meta.ref.urlchar_RAPosition (derived from RXJ name) (right ascension part)degpos.eq.ra;meta.main_DEPosition (derived from RXJ name) (declination part)degpos.eq.dec;meta.main