J/MNRAS/512/3858ivo://CDS.VizieR/J/MNRAS/512/3858doi:10.26093/cds/vizier/bg-g0-3rjCDSLi D.Starling R.L.C.Saxton R.D.Pan H.-W.Yuan W.2026-08-03T07:31:21Z2025-03-28T13:34:40ZCDS support team

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

cds-question@unistra.frx-ray-sourcesastrometryastronomical-object-identificationphotometryredshiftedWe present the identifications of a flux-limited sample of highly variable X-ray sources on long time-scales from the second catalogue of the XMM-Newton SLew survey (XMMSL2). The carefully constructed sample, comprising 265 sources (2.5 per cent) selected from the XMMSL2 clean catalogue, displayed X-ray variability of a factor of more than 10 in 0.2-2 keV compared to the ROSAT All Sky Survey. Of the sample sources, 94.3 per cent are identified. The identification procedure follows a series of cross-matches with astronomical data bases and multiwavelength catalogues to refine the source position and identify counterparts to the X-ray sources. Assignment of source type utilizes a combination of indicators including counterparts offset, parallax measurement, spectral colours, X-ray luminosity, and light-curve behaviour. We identified 40 per cent of the variables with stars, 10 per cent with accreting binaries, and at least 30.4 per cent with active galactic nuclei. The rest of the variables are identified as galaxies. It is found that the mean effective temperatures of the highly variable stars are lower than those of less variable stars. Our sample of highly variable AGN tend to have lower black hole masses, redshifts, and marginally lower soft X-ray luminosities compared to the less variable ones, while no difference was found in the Eddington ratio distributions. Five flaring events are tidal disruption events published previously. This study has significantly increased the number of variable sources in XMMSL2 with identifications and provides greater insight on the nature of many o f the sources, enabling further studies of highly variable X-ray sources.2022MNRAS.512.3858Lhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/MNRAS/512/3858CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toJ/MNRAS/473/4937 : AllWISE ctp to ROSAT/2RXS & XMMSLEW2 catalogsJ/A+A/588/A103 : Second ROSAT all-sky survey (2RXS) source catalogJ/A+A/403/247 : Variability in the ROSAT All-Sky Survey (Fuhrmeister+, 2003)J/A+A/480/611 : XMM-Newton Slew Survey catalogue, XMMSL1 (Saxton+, 2008)J/ApJ/792/30 : NEOWISE magnitudes for near-Earth objects (Mainzer+, 2014)IX/10A : ROSAT All-Sky Bright Source Catalogue (1RXS) (Voges+ 1999)V/147 : The SDSS Photometric Catalogue, Release 12 (Alam+, 2015)IX/66 : 4XMM-DR11s serendipitous source catalogue from stacksIX/53 : XMM-Newton slew survey Source Catalogue, version 2.0II/328 : AllWISE Data Release (Cutri+ 2013)I/345 : Gaia DR2 (Gaia Collaboration, 2018)IX/58 : 2SXPS Swift X-ray telescope point source catalogueIX/55 : XMM-Newton Serendipitous Source Catalogue 3XMM-DR8IX/59 : XMM-Newton Serendipitous Source Catalogue 4XMM-DR9https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/MNRAS/512/3858https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/MNRAS/512/3858http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/MNRAS/512/3858https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/MNRAS/512/3858https://vizier.iucaa.in/viz-bin/votable?-source=J/MNRAS/512/3858http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/MNRAS/512/3858GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/MNRAS/512/3858/table (Photometric properties of out XMMSL2 variable sources sample)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/MNRAS/512/3858/table?https://vizier.iucaa.in/viz-bin/conesearch/J/MNRAS/512/3858/table?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/MNRAS/512/3858/table?GETtext/xml+votable180.050000true2.50649547-43.159554040.0055555555555555566/341 873 907 2228 2621 2809 3017 3269 3338 3971 4475 5487 5671 5750 7049 7377 8006 8216 8690 8794 9005 9639 9691 10046 10055 10063 10077 10098 10153 10168-10169 10175 10190 10205 10511 11035 11071 11359 11490 11577 11584 11605 11623 11631 11653 11678 11696 11717 11732 11820 11824 12050 12123 12250-12251 12329 12719 13022 13283 13301 13968 14751 14808 14847 14929 15038 15090 15127 15135 15141 15154 15213 15269 15280 15308 15317 15344 15357 15367 15532 15700 15867 15896 15964 16028 16034 16043-16044 16059 16080 16257 16259 16272 16301 16316 16327 16332-16333 16361 17162 17503 17668 18431 20359 20602 20825 21020 21439 21615 21626 21847 22111 22145 22279 22863 23689 24932 25153 25963 25967 27474 27478 27913 28176 28221 28261 28522 28798 28950 29285 29691 30500 30577 30780 31191 31334 31590 31873 32353 32370 32890 32931 33072-33073 33078-33079 33090 33094-33095 33112-33113 33115-33117 33120 33133 33136-33137 33155 33211 33234 33298 33728 33746 33768 33799 33806 33811 33881 34062 34252 34294 34398 34422 35489 35730 35850 35984 36443 36897 36976 37079 37203 37252 37398 37426 37429 37432 37464 37477 37481 37488 37508 37512 37518 37545 37549 37561 37604 37613 37636 37650 37897 37907 38331 38839 38944 38949 38954 38961 39000 39008 39045 39054-39055 39066 39075 39168 39254 39311 39522 39545 39566 39589 39840 40131 40167 40294 41274 41482 41508 41510 41823 41871 42012 42133 42159 42163 42311 42314 42396 42555 42748 42756 42815 42929 42956 43009 43412 44033 44341 44378 44414 45388 45398 47425 48638https://cdsarc.cds.unistra.fr/viz-bin/moc/J/MNRAS/512/3858?format=asciiX-raydefaultJ/MNRAS/512/3858/tablePhotometric properties of out XMMSL2 variable sources sampleSimbadNameSimbad column added by the CDSmeta.idcharnullableTypeType of the identifier (ID_TYPE)src.classcharrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintRAJ2000Right ascension (J2000) (XMMSL2_RA)degpos.eq.ra;meta.mainDEJ2000Declination (J2000) (XMMSL2_DEC)degpos.eq.dec;meta.mainFXMMThe 0.2-2 keV source soft band flux in the XMMSL2 (FLUX_XMMSL2) (1)mW.m**-2phot.flux;em.X-ray.softdoublee_FXMMThe error on the XMMSL2 soft band flux FX (FLUX_XMMSL2_ERR)mW.m**-2stat.errordoubleExtThe spatial extension of the source in the XMMSL2 soft band (EXT_XMMSL2)pixphys.angSizedoubleDetMLThe detection likelihoods in the XMMSL2 soft band (DET_ML_XMMSL2)stat.likelihooddoubleFXRASSThe 0.2-2 keV source soft band flux in the RASS at the XMMSL2 source position (FLUX_RASS)mW.m**-2phot.flux;em.X-ray.softdoublee_FXRASSThe error on the RASS soft flux FXRASS, 0 means that FXRASS is an upper limit (FLUX_RASS_ERR)mW.m**-2stat.errordoubleFXMM/FXRASSThe flux ratio between FXMM and FXRASS (FLUX_RATIO)phot.flux;arith.ratio;em.X-ray.softdoubleRACdeg? Right ascension of the identifier (J2000) (IDENTIFIER_RA)degpos.eq.ranullableDECdeg? Declination (J2000) (IDENTIFIER_DEC)degpos.eq.decnullablez? Redshift of the galaxies and AGN when available in SIMBAD/NED (z)src.redshiftfloatnullablet? Time range when the fluxes of flaring galaxies declined by a factor of 10yrtime.epochfloatnullableXMMSL2Official name for sources detected in the XMM-Newton slew survey (XMMSL2_unique_name)meta.id;meta.maincharCrossIDThe catalogue name of the best cross-match (IDENTIFIER)meta.id;meta.tablecharf_TypeFlag for the type for each source (ID_FLAG) (2)meta.codecharr_CrossIDThe astronomical data base or catalogue from which the best match has been selected (ID_RESOURCE) (3)meta.ref;pos.framechar