J/MNRAS/501/2790ivo://CDS.VizieR/J/MNRAS/501/2790doi:10.26093/cds/vizier/bg-fn-2q6CDSBahramian A.Heinke C.O.Kennea J.A.Maccarone T.J.Evans P.A.,Wijnands R.Degenaar N.in't Zand J.J.M.Shaw A.W.,Rivera Sandoval L.E.McClure S.Tetarenko A.J.Strader J.Kuulkers E.,Sivakoff G.R.2026-08-03T07:30:53Z2023-11-15T08:22:24ZCDS support team

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

cds-question@unistra.frx-ray-sourcesaccretionactive-galactic-nucleix-ray-binary-starsmilky-way-galaxyvisible-astronomyVery faint X-ray transients (VFXTs) are X-ray transients with peak X-ray luminosities (L_X_) of L_X_~<10^36^erg/s, which are not well understood. We carried out a survey of 16 deg^2^ of the Galactic Bulge with the Swift Observatory, using short (60s) exposures, and returning every 2 weeks for 19 epochs in 2017-18 (with a gap from 2017 November to 2018 February, when the Bulge was in sun-constraint). Our main goal was to detect and study VFXT behaviour in the Galactic Bulge across various classes of X-ray sources. In this work, we explain the observing strategy of the survey, compare our results with the expected number of source detections per class, and discuss the constraints from our survey on the Galactic VFXT population. We detected 91 X-ray sources, 25 of which have clearly varied by a factor of at least 10. In total, 45 of these X-ray sources have known counterparts: 17 chromospherically active stars, 12 X-ray binaries, 5 cataclysmic variables (and 4 candidates), 3 symbiotic systems, 2 radio pulsars, 1 active galactic nuclei, and a young star cluster. The other 46 are of previously undetermined nature. We utilize X-ray hardness ratios, searches for optical/infrared counterparts in published catalogues, and flux ratios from quiescence to outburst to constrain the nature of the unknown sources. Of these 46, 7 are newly discovered hard transients, which are likely VFXT X-ray binaries. Furthermore, we find strong new evidence for a symbiotic nature of four sources in our full sample, and new evidence for accretion power in six X-ray sources with optical counterparts. Our findings indicate that a large subset of VXFTs is likely made up of symbiotic systems.2021MNRAS.501.2790Bhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/MNRAS/501/2790CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toIX/57 : The Chandra Source Catalog (CSC), Release 2.0 (Evans+, 2019)IX/55 : XMM-Newton Serendipitous Source Catalogue 3XMM-DR8 (XMM-SSC, 2018)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/MNRAS/501/2790https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/MNRAS/501/2790http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/MNRAS/501/2790https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/MNRAS/501/2790https://vizier.iucaa.in/viz-bin/votable?-source=J/MNRAS/501/2790http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/MNRAS/501/2790GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/MNRAS/501/2790/catalog (Swift Bulge Survey X-ray Source catalogue)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/MNRAS/501/2790/catalog?https://vizier.iucaa.in/viz-bin/conesearch/J/MNRAS/501/2790/catalog?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/MNRAS/501/2790/catalog?GETtext/xml+votable180.050000true266.76118-28.88330.0055555555555555565/7207 7212-7213 6/28817-28819 28822-28823 28825-28827 28837 28839 28866 28872https://cdsarc.cds.unistra.fr/viz-bin/moc/J/MNRAS/501/2790?format=asciiX-rayOpticaldefaultJ/MNRAS/501/2790/catalogSwift Bulge Survey X-ray Source catalogueSimbadNameSimbad column added by the CDSmeta.idcharnullablerecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintSBSXNumber in the Swift Bulge Survey Catalogmeta.idintRAJ2000Right ascension (J2000)degpos.eq.ra;meta.mainDEJ2000Declination (J2000)degpos.eq.dec;meta.mainPoserr90% uncertainty radius on source localizationstat.errorfloatPeakratePeak net count rate in the SBS datact/sphot.count;em.X-rayfloate_PeakrateError on Peakrate (1-{sigma} uncertainty)ct/sstat.errorfloatHardnessSource spectral hardness (1)phot.flux;arith.ratiofloate_Hardness1-{sigma} lower error on Hardnessstat.error;phot.fluxfloatE_Hardness1-{sigma} upper error on Hardnessstat.error;stat.maxfloatNdet? Number of SBS epochs in which the source is detectedmeta.numberintnullableNobs? Number of SBS epochs in which the source area is coveredmeta.numberintnullablevarsigma? Significance of source flux variation in the SBS data Var{sigma} (2)stat.fit.goodnessfloatnullableNHBest-fit hydrogen column density for the merged source spectrumcm**-2phys.columnDensity;meta.modelleddoublee_NHLower 90% error on NHcm**-2stat.errordoubleE_NHUpper 90% error on NHcm**-2stat.error;stat.maxdoubleGammaBest-fit photon index for the merged source spectrum {Gamma}meta.code;spect.index;meta.modelledfloate_GammaLower 90% error on Gammastat.errorfloatE_GammaUpper 90% error on Gammastat.error;stat.maxfloatFunabsBest-fit unabsorbed flux for the merged source spectrummW.m**-2phot.flux;em.X-raydoublee_FunabsLower 90% error on FunabsmW.m**-2stat.errordoubleE_FunabsUpper 90% error on FunabsmW.m**-2stat.error;stat.maxdoubleFabsBest-fit absorbed flux for the merged source spectrummW.m**-2phot.flux;em.X-raydoublee_FabsLower 90% error on FabsmW.m**-2stat.errordoubleE_FabsUpper 90% error on FabsmW.m**-2stat.error;stat.maxdoublePeakabsPeak absorbed flux (3)mW.m**-2phot.flux;em.X-raydoublee_Peakabs1-{sigma} error on PeakabsmW.m**-2stat.errordoubleFacis? Cataloged ACIS flux in the "broad" bandmW.m**-2phot.flux;em.X-raydoublenullableb_Facis? Lower bound on FacismW.m**-2phot.flux;em.X-ray;stat.mindoublenullableB_Facis? Upper bound on FacismW.m**-2phot.flux;em.X-ray;stat.maxdoublenullableFhrc? Cataloged HRC flux in the "wide" bandmW.m**-2phot.flux;em.X-raydoublenullableb_Fhrc? Lower bound on FhrcmW.m**-2phot.flux;em.X-ray;stat.mindoublenullableB_Fhrc? Upper bound on FhrcmW.m**-2phot.flux;em.X-ray;stat.maxdoublenullableFepic? Cataloged XMM-Newton/EPIC flux averaged among all EPIC camerasmW.m**-2phot.flux;em.X-raydoublenullablee_Fepic? Error on FepicmW.m**-2stat.errordoublenullablechi2XMM? Cataloged chi2 probability that the time series of the source can be explained by a constant fluxstat.fit.chi2doublenullableFsbs/Facis? Flux ratio between the peak flux in the SBS and the cataloged ACIS fluxphot.flux;arith.ratiodoublenullablee_Fsbs/Facis? 1-{sigma} error on Fsbs/Facisstat.errordoublenullableFsbs/Fhrc? Flux ratio between the peak flux in the SBS and the cataloged HRC fluxphot.flux;arith.ratiodoublenullablee_Fsbs/Fhrc? 1-{sigma} error on Fsbs/Fhrcstat.errordoublenullableFsbs/Fepic? Flux ratio between the peak flux in the SBS and the cataloged EPIC fluxphot.flux;arith.ratiodoublenullablee_Fsbs/Fepic? 1-{sigma} error on Fsbs/Fepicstat.errordoublenullableVmag? V-band magnitude of the likely optical counterpartmagphot.mag;em.opt.VfloatnullableKmag? K-band magnitude of the likely optical counterpartmagphot.mag;em.IR.KfloatnullablelogFX/FV? Logarithm of the ratio of the average X-ray flux to the optical fluxphot.flux;arith.ratiodoublenullableSwiftOfficial Swift designation JHHMMSS.s_DDMMSSmeta.id;meta.maincharONameAlternative identificationmeta.idcharTypeNature of the X-ray sourcesrc.classcharCommentComment on the nature and behavior of the sourcemeta.notecharFlagQuality of the detection as determined by the Swift/XRT analysis pipelinemeta.code.qualcharChandraChandra designation for a counterpart identified within the SBS source error circle (4)meta.idcharXMMXMM-Newton designation for a counterpart identified within the SBS source error circle (5)meta.idchar