J/A+A/693/A62ivo://CDS.VizieR/J/A+A/693/A62doi:10.26093/cds/vizier.36930062CDSGrotova I.Rau A.Salvato M.Buchner J.Goodwin A.J.Liu Z.,Malyali A.Merloni A.Tubin-Arenas D.Homan D.Krumpe M.Nandra K.,Shirley R.Anderson G.E.Arcodia R.Bahic S.Baldini P.Buckley D.A.H.,Ciroi S.Kawka A.Masterson M.Miller-Jones J.C.A.Di Mille F.2025-03-03T20:01:45Z2025-01-03T15:04:01ZCDS support team

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

cds-question@unistra.frsurveysx-ray-sourcesThe eROSITA telescope aboard the Spectrum Roentgen Gamma (SRG) satellite provides an unprecedented opportunity to explore the transient and variable extragalactic X-ray sky due to the sensitivity, sky coverage, and cadence of the all-sky survey. While previous studies showed the dominance of regular active galactic nuclei (AGN) variability, a small fraction of sources expected in such a survey arise from more exotic phenomena such as tidal disruption events (TDEs), quasi-periodic eruptions, or other short-lived events associated with supermassive black hole accretion. This paper describes the systematic selection of X-ray extragalactic transients found in the first two eROSITA all-sky surveys (eRASS) that are not associated with known AGN prior to eROSITA observations. We generate a variability sample using the data from the first and second eRASS, which includes sources with variability significance and fractional amplitude larger than four in the 0.2-2.3keV energy band, discovered between December 2019 and December 2020, and located in the Legacy Survey DR10 (LS10) footprint. When possible, transients are associated with optical LS10 counterparts. The properties of these counterparts are used to exclude stars and known active galaxies. The sample is additionally cleaned from known AGN using pre-eROSITA SIMBAD and the Million Quasars Catalog (Milliquas) classifications, archival optical spectra, and archival X-ray data. We explore archival X-ray variability, long-term (2-2.5 years) eROSITA light curves, and peak X-ray spectra to characterize the X-ray properties of the sample. Sources with radio counterparts are identified using the Rapid ASKAP Continuum Survey (RACS) and Karl G. Jansky Very Large Array Sky Survey (VLASS). We present a catalog of 304 extragalactic eROSITA transients and variables not associated with known AGN, called eRO-ExTra. More than 90% of sources are associated with reliable LS10 optical counterparts. For each source, we provide archival X-ray data from Swift, ROSAT, and XMM-Newton, the eROSITA long-term light curve with light curve classification, as well as the best power law fit spectral results at the peak eROSITA epoch. Reliable spectroscopic and photometric redshifts, both archival and from follow-up data, are provided for more than 80% of the sample. Several sources in the catalog are eROSITA discovered known TDE candidates. In addition, 31 sources are radio detected. The origin of radio emission needs to be further identified. The eRO-ExTra transients constitute a relatively clean parent sample of non-AGN variability phenomena associated with massive black holes. The eRO-ExTra catalog includes more than 95% of sources discovered in X-rays with eROSITA for the first time, making it a valuable resource for studying unique nuclear transients.2025A&A...693A..62Ghttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/693/A62CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toJ/A+A/682/A34 : SRG/eROSITA all-sky survey catalogs (eRASS1) (Merloni+, 2024)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/693/A62https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/693/A62http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/693/A62https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/693/A62https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/693/A62http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/693/A62GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/693/A62/catalog (eRO-ExTra catalog)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/693/A62/catalog?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/693/A62/catalog?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/693/A62/catalog?GETtext/xml+votable180.050000true0.7411180461535-40.33086651370920.0055555555555555566/4168 4426 4484 4713 5168 6244 10241 16385 16415 16423 16425 20498 20610 20626 20662-20663 20670 20672 20731 21030 21033 21122 21161 21977 22010 22373 22607 23113 23260 24609 24678 24697 24799 24856 24868 24894 24966 25029 25056 25324 25471 25506 25517 25558 25684 25731 25812 25959 26151 26186 26192 26205 26227 26239 26450 26648 26711 26915 27244 27688 27787 27983 27985 28441 32791 32805 32812 32854 32884 32981 32988 33013 33072 33080 33118 33133-33134 33137 33139 33170 33179 33190 33221 33245 33247 33273 33345 33415 33533 33566 33580 33603 33642 33665 33707 33747 33767 33806 33821 33824 33829 33833 33838 33855 33859 33861 33879 33890 33907-33908 33927 33951 33961 33967 33981 33992 34005 34012 34111 34117 34150 34154 34189 34240 34249 34275 34294 34300 34310 34316 34325 34360 34460 34477 34507 34526 34547 34564 34586 34611 34618 34628 34673 34679 34702 34713 34721 34766 34774 34840 34871 34880 34910 35080 35097 35160 35211 35233 35451 35460 35740 35744 35763 35874 35876 35892 35955 35984 35999 36045 36068 36146 36203 36225 36238 36285 36348 36531 36610 36660 36701 36801 36807 36817 36886 36890 36894 36905-36906 36913 36918 36926 37007 37017-37018 37038 37053 37065 37124 37391 37418 37420 37423 37427-37428 37439 37442 37480 37505 37507 37520 37543 38289 38854 38890 38922 38932 38934 38936 38939 38969 38974 39008 39048 39065 39076 39098 39464 39558 39563 39592 40892 40979-40980 41022 41058 41111 41137 41153 41270 43494 43543 43618 43620 43662 43744 43777 43792 43800 43826 43828 43840 43966 44012 44153 44168 44201 44214 44226 44236 44564 44573 44588 44598 44659 44687 44741 44809 44892 45067 45203 45262 45322 45440 45612 45736 45739 45859 45879 46095 46106 46117 46273 46293 46306 46349 46355 46391 46417 46468 46486 46495 46501 46619 47208 47303 47420 474365.830941190275487e-25 1.987820871092403e-24https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/693/A62?format=asciiX-raydefaultJ/A+A/693/A62/catalogeRO-ExTra catalogDETdeg? TNS Declination (TNS_DEC)degpos.eq.decnullableTNSDate? MJD TNS discovery date (TNS_DATE)dtime.epochdoublenullableSTypeSIMBAD main type (SIMBAD_TYPE)src.classcharRATdeg? TNS Right Ascension (TNS_RA)degpos.eq.ranullablee_FeRASS5? Error flux (68%) in energy band 0.2-2.3keV in eRASS5 (ERO_FLUX_ERR_eRASS5)mW.m**-2stat.errordoublenullableAmpAmplitude of variability between eRASS1 and eRASS2 (Amplitude)src.var.amplitudedoubleSigniSignificance of variability between eRASS1 and eRASS2 (Significance)stat.fit.goodness;src.vardoubleLCClass[1/4] eROSITA lightcurve class (ERO_LCCLASS) (1)meta.code.classintERODateMJD dates of eROSITA observations: (MJD_1,..,MJD_<N>), N =1,2,3,4, (5, if available) (ERO_DATE)dtime.epochcharNHGalactic equivalent neutral hydrogen column density in the line of sight (NH)cm**-2phys.columnDensity;pos.galactic;spect.linedoubleGammaPhoton index for the peak eRASS (ERO_GAMMA)meta.code;spect.indexdoublee_FModError flux (68%) in energy band 0.2-2.3keV for the peak eRASS (ERO_FLUX_MOD_ERR)mW.m**-2stat.errordoubleARCHFlag[0/2] Archival X-ray constraints (ARCH_FLAG) (2)meta.codefloatARCHDateMJD dates of N archival observations: (X_1,..,X_<N>) (ARCH_DATE)dtime.epochcharARCHFluxSource flux of N archival observations: (F_1,..,F_<N>) in energy band 0.2-2.0keV (ARCH_FLUX)mW.m**-2phot.flux;em.X-raychare_ARCHFluxError flux (68%) of N archival observations: (F_err_1,..,F_err_<N>) in energy band 0.2-2.0keV; -1=flux upper limit (99.7%) (ARCH_FLUX_ERR)mW.m**-2stat.errorcharARCHInstInstruments of N archival observations (Instrument_1,.., Instrument_<N>) (ARCH_INSTRUMENT)meta.id;instrcharbiasProbability weighting introduced by Xray_proba prior (NWAY_bias_LS10_Xray_proba) (3)stat.fit.goodnessdoublerecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintEROOfficial IAU name of the source from Merloni et al. (2024A&A...682A..34M) or source name in the format eRASSU Jhhmmss.s-ddmmss (ERO_NAME)meta.id;meta.maincharRA_ICRSeROSITA Right Ascension (ICRS) from eRASS:5 (cumulative catalogue of 4(5) eRASS) (ERO_RA)degpos.eq.ra;meta.mainDE_ICRSeROSITA Declination (ICRS) from eRASS:5 (ERO_DEC)degpos.eq.dec;meta.mainePos1-sigma position uncertainty from eRASS:5 (ERO_POSERR)arcsecstat.error;posdoubleFeRASS1Source flux in energy band 0.2-2.3keV in eRASS1 (ERO_FLUX_eRASS1)mW.m**-2phot.flux;em.X-raydoublee_GammaError photon index (68%) for the peak eRASS (ERO_GAMMA_ERR)stat.errordoubleFModSource flux in energy band 0.2-2.3keV for the peak eRASS (ERO_FLUX_MOD)mW.m**-2phot.flux;em.X-raydoubleFIvarW2Inverse variance of flux W2 (LS10_FLUX_IVAR_W2)3.63uJy**-2stat.fit.paramdoubleTNSTransient Name Server (TNS) source name (TNS_NAME)meta.idcharMWtransg[0/1] Galactic transmission in g filter in linear units (LS10_MW_TRANSMISSION_G)phys.transmission;pos.galacticdoubleFeRASS2Source flux in the energy band 0.2-2.3keV in eRASS2 (ERO_FLUX_eRASS2)mW.m**-2phot.flux;em.X-raydoubleFeRASS3? Source flux in the energy band 0.2-2.3keV in eRASS3 (ERO_FLUX_eRASS3)mW.m**-2phot.flux;em.X-raydoublenullableFeRASS4? Source flux in the energy band 0.2-2.3keV in eRASS4 (ERO_FLUX_eRASS4)mW.m**-2phot.flux;em.X-raydoublenullableFeRASS5? Source flux in the energy band 0.2-2.3keV in eRASS5 (ERO_FLUX_eRASS5)mW.m**-2phot.flux;em.X-raydoublenullablel_FeRASS1[u] u for upper limit flux (99.7%) in FeRASS1meta.code.errorchare_FeRASS1? Error flux (68%) in energy band 0.2-2.3keV in eRASS1 (ERO_FLUX_ERR_eRASS1)mW.m**-2stat.errordoublenullablel_FeRASS2[u] u for upper limit flux (99.7%) in FeRASS2meta.code.errorchare_FeRASS2? Error flux (68%) in energy band 0.2-2.3keV in eRASS2 (ERO_FLUX_ERR_eRASS2)mW.m**-2stat.errordoublenullablel_FeRASS3[u] u for upper limit flux (99.7%) in FeRASS3meta.code.errorchare_FeRASS3? Error flux (68%) in energy band 0.2-2.3keV in eRASS3 (ERO_FLUX_ERR_eRASS3)mW.m**-2stat.errordoublenullablel_FeRASS4[u] u for upper limit flux (99.7%) in FeRASS4meta.code.errorchare_FeRASS4? Error flux (68%) in energy band 0.2-2.3keV in eRASS4 (ERO_FLUX_ERR_eRASS4)mW.m**-2stat.errordoublenullablel_FeRASS5[u] u for upper limit flux (99.7%) in FeRASS5meta.code.errorcharDistFaclogarithm of the ratio of the prior and posterior from separation, positional error, and number density (NWAY_dist_bayesfactor) (3)stat.fit.paramdoubleDistPostDistance posterior probability comparing this association vs. no association (NWAY_dist_post) (3)stat.fit.paramdoublepsingleDistance posterior probability comparing this association vs. no association weighted by the prior (NWAY_p_single) (3)stat.fit.paramdoublepanyFor each entry in the X-ray catalogue, the probability that there is a counterpart (NWAY_p_any) (3)stat.fit.paramdoublepiRelative probability of the eROSITA/LS10 match (NWAY_p_i) (3)stat.fit.goodnessdoubleLRelInteger denoting the camera and filter set used in Legacy survey DR10 (LS10), which will be unique for a given processing run of data (LS10_RELEASE)meta.id;instrintLBrickIDLS10 Brick ID (LS10_BRICKID)meta.idintLObjIDCatalog object number within this LS10 brick (LS10_OBJID)meta.idintRALdegRight Ascension (J2000) of the LS10 counterpart (LS10_RA)degpos.eq.raDELdegDeclination (J2000) of the LS10 counterpart (LS10_DEC)degpos.eq.decLRAIvarInverse variance of RA, excluding astrometric calibration errors (LS10_RA_IVAR)deg**-2stat.fit.paramdoubleLDEIvarInverse variance of DEC, excluding astrometric calibration errors (LS10_DEC_IVAR)deg**-2stat.fit.paramdoubleFgLS10 model flux g (LS10_FLUX_G)3.63uJyphot.mag;em.opt.BdoubleFrLS10 model flux r (LS10_FLUX_R)3.63uJyphot.mag;em.opt.RdoubleFiLS10 model flux i (LS10_FLUX_I)3.63uJyphot.mag;em.opt.IdoubleFzLS10 model flux z (LS10_FLUX_Z)3.63uJyphot.mag;em.opt.IdoubleFW1LS10 model flux W1 (LS10_FLUX_W1)3.63uJyphot.mag;em.IR.3-4umdoubleFW2LS10 model flux W2 (LS10_FLUX_W2)3.63uJyphot.mag;em.IR.4-8umdoubleFIvargInverse variance of flux g (LS10_FLUX_IVAR_G)3.63uJy**-2stat.fit.paramdoubleFIvarrInverse variance of flux r (LS10_FLUX_IVAR_R)3.63uJy**-2stat.fit.paramdoubleFIvariInverse variance of flux r (LS10_FLUX_IVAR_I)3.63uJy**-2stat.fit.paramdoubleFIvarzInverse variance of flux z (LS10_FLUX_IVAR_Z)3.63uJy**-2stat.fit.paramdoubleFIvarW1Inverse variance of flux W1 (LS10_FLUX_IVAR_W1)3.63uJy**-2stat.fit.paramdoubleMWtransr[0/1] Galactic transmission in r filter in linear units (LS10_MW_TRANSMISSION_R)phys.transmission;pos.galacticdoubleMWtransi[0/1] Galactic transmission in i filter in linear units (LS10_MW_TRANSMISSION_I)phys.transmission;pos.galacticdoubleMWtransz[0/1] Galactic transmission in z filter in linear units (LS10_MW_TRANSMISSION_Z)phys.transmission;instr.filterdoubleMWtransW1[0/1] Galactic transmission in W1 filter in linear units (LS10_MW_TRANSMISSION_W1)phys.transmission;pos.galacticdoubleMWtransW2[0/1] Galactic transmission in W2 filter in linear units (LS10_MW_TRANSMISSION_W2)phys.transmission;pos.galacticdoubleMTypeMorphological model from LS10 (LS10_TYPE)src.morph.type;meta.modelledcharz? Redshift (Z_REDSHIFT)src.redshiftdoublenullablezTypeRedshift type: photoz = photometric, specz = spectroscopic (Z_TYPE)meta.codecharr_zRedshift origin (Z_REFERENCE)meta.ref;pos.framecharSNameSIMBAD source ID (SIMBAD_NAME)meta.idcharRASdeg? SIMBAD Right Ascension (J2000) (SIMBAD_RA)degpos.eq.ranullableDESdeg? SIMBAD Declination (J2000) (SIMBAD_DEC)degpos.eq.decnullableVLASSThe Very Large Array Sky Survey (VLASS) (VLASS_NAME)meta.idcharRAVdeg? VLASS Right Ascension (VLASS_RA)degpos.eq.ranullableDEVdeg? VLASS Declination (VLASS_DEC)degpos.eq.decnullableFVLASS? VLASS total flux density at 3GHz (VLASS_FLUX)mJyphot.flux.density;em.radio.1500-3000MHzdoublenullableRACSRapid ASKAP Continuum Survey (RACS) (RACS_NAME)meta.idcharRARdeg? RACS Right Ascension (RACS_RA)degpos.eq.ranullableDERdeg? RACS Declination (RACS_DEC)degpos.eq.decnullableFRACS? RACS total flux density at 0.88GHz (RACS_FLUX)mJyphot.flux.density;em.radio.750-1500MHzfloatnullableCstatDOFC-statistic per degree of freedom, used to assess the goodness of fit (ERO_CSTAT_DOF)stat.fit.dofchar