J/AN/321/81ivo://CDS.VizieR/J/AN/321/81doi:10.26093/cds/vizier.113210081CDSLohmann P.Wendker H.J.2025-09-29T20:17:17Z2000-10-23T13:42:03ZCDS support team

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

cds-question@unistra.fropen-star-clustersx-ray-sourcespre-main-sequence-starsA deep ROSAT PSPC image centred on the Orion Trapezium has been reduced a second time using an improved version of the PSF to fit the data. The outer rim of the field of view was also included. The new catalogue contains 316 X-ray sources which are easily identified with pre-main sequence stars of the Ori OB1 Ic and Id association. All 316 sources were tested for variability. No variations were found inside the single exposures of about 45 minutes length each. Between the 4 exposures spaced over 5 days about 1/3 of the sources show signs of activities of various forms. As above 25% of these have somewhat regular lights curves (monotonically rising or falling or hill- shaped) we infer that at least some outbursts with time scales longer than a day are present and that past searches for X-ray flares of pre-main sequence stars were biased towards shorter time scales.2000AN....321...81Lhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/AN/321/81CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toIX/30 : Second ROSAT PSPC Catalog (ROSAT, 2000)IX/31 : The WGACAT version of ROSAT sources (White+ 2000)IX/32 : ROSAT Bright Survey (Fischer+, 1998-2000)J/A+A/299/39 : Orion Trapezium area ROSAT PSPC obs. I. (Geier+, 1995)J/ApJ/540/1016 : K-band & NICMOS phot. of Trapezium Cluster (Luhman+, 2000)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/AN/321/81https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/AN/321/81http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/AN/321/81https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/AN/321/81https://vizier.iucaa.in/viz-bin/votable?-source=J/AN/321/81http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/AN/321/81GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/AN/321/81/table1 (Properties of ROSAT PSPC X-ray sources in the Orion Trapezium area)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/AN/321/81/table1?https://vizier.iucaa.in/viz-bin/conesearch/J/AN/321/81/table1?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/AN/321/81/table1?GETtext/xml+votable180.050000true83.974583-5.0777780.005555555555555556ROSAT5/5359 6/22804-22805https://cdsarc.cds.unistra.fr/viz-bin/moc/J/AN/321/81?format=asciiX-raydefaultJ/AN/321/81/table1Properties of ROSAT PSPC X-ray sources in the Orion Trapezium arearecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintROS-ORI[1/316]+ Sequential number (1)meta.id;meta.mainintprimaryindexedn_ROS-ORI[*] indicates a note in notes.dat filemeta.notecharRAJ2000Right ascension (J2000.0)pos.eq.ra;meta.mainDEJ2000Declination (J2000.0)pos.eq.dec;meta.mainphiOff-axis anglearcmininstr.offsetfloatetaSource count ratect/ksphot.count;em.X-rayfloatS/NSignal to noise ratiostat.snrfloatRXApparent source radius (2)arcsecphys.angSizefloatHR2Hardness ratio HR2 (3)phot.flux;arith.ratiofloate_HR2rms uncertainty on HR2stat.errorfloatVar[PV] Variablity type (4)meta.notecharRemRemarks (5)meta.notecharJ/AN/321/81/notesRemarks on individual sources (table2)recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintROS-ORISequential numbermeta.id;meta.mainintRemText of the remarkmeta.notechar