J/AJ/110/1229ivo://CDS.VizieR/J/AJ/110/1229doi:10.26093/cds/vizier.51101229CDSProsser C.F.Stauffer J.R.Caillault J.-P.Balachandran S.,Stern R.A.Randich S.2023-04-06T16:50:17Z1998-08-31T12:09:38ZCDS support team

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

cds-question@unistra.fropen-star-clustersx-ray-sourcesccd-photometryA ROSAT X-ray survey, with complementary optical photometry, of the open cluster NGC 6475 has enabled the detection of ~50 late-F to K0 and ~70 K/M dwarf new candidate members, providing the first reliable detection of low-mass stars in this low galactic latitude, 220Myr old cluster. The X-ray observations reported here have a typical limiting sensitivity of L_X_ ~ 10^29^erg/s. The detection frequency of early type cluster members is consistent with the hypothesis that the X-ray emitting early type stars are binary systems with an unseen, low-mass secondary producing the X-rays. The ratio between X-ray and bolometric luminosity among NGC 6475 members saturates at a spectral-type/color which is intermediate between that in much younger and in much older clusters, consistent with rotational spindown of solar-type stars upon their arrival on the ZAMS. The upper envelope of X-ray luminosity as a function of spectral type is comparable to that of the Pleiades, with the observed spread in X-ray luminosity among low-mass members being likely due to the presence of binaries and relatively rapid rotators. However, the list of X-ray selected candidate members is likely biased against low-mass, slowly rotating single stars. While some preliminary spectroscopic information is given in an appendix, further spectroscopic observations of the new candidate members will aid in interpreting the coronal activity among solar-type NGC 6475 members and their relation to similar stars in older and younger open clusters.1995AJ....110.1229Phttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/AJ/110/1229CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicehttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/AJ/110/1229https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/AJ/110/1229http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/AJ/110/1229https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/AJ/110/1229https://vizier.iucaa.in/viz-bin/votable?-source=J/AJ/110/1229http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/AJ/110/1229GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/AJ/110/1229/table4 (X-ray source list)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/AJ/110/1229/table4?https://vizier.iucaa.in/viz-bin/conesearch/J/AJ/110/1229/table4?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/AJ/110/1229/table4?GETtext/xml+votable180.050000true267.899167-34.7541670.005555555555555556Cone search capability for table J/AJ/110/1229/table5 (X-ray source list: Weaker possible sources)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/AJ/110/1229/table5?https://vizier.iucaa.in/viz-bin/conesearch/J/AJ/110/1229/table5?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/AJ/110/1229/table5?GETtext/xml+votable180.050000true268.138333-34.9044440.005555555555555556ROSAT6/28709-28711 28717 28722https://cdsarc.cds.unistra.fr/viz-bin/moc/J/AJ/110/1229?format=asciiX-raydefaultJ/AJ/110/1229/table4X-ray source listrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintIDIdentification number [PSC95]meta.id;meta.mainintRA2000Right ascension (2000)pos.eq.ra;meta.mainDE2000Declination signpos.eq.dec;meta.mainOff-axisDistance off-axis from the center of the PSPC fieldarcmininstr.offsetfloatExpExposition timestime.duration;obs.exposureintCRateCount rates**-1phot.count;em.X-rayfloate_CRaterms uncertainty on CRates**-1stat.errorfloatS/NbBroadband (0.07-2.4keV) signal to noise ratiostat.snrfloatS/NhHardband (0.5-1.8keV) signal to noise ratiostat.snrfloatlogLxX-ray luminositylog(1e-07W)phys.luminosity;em.X-rayfloatl_HR[>= ] Limit flag on HRmeta.code.errorcharHR? Hardness ratiophot.flux;arith.ratiofloatnullableDRA? Offset on right ascension between X-ray and optical positionsarcsecpos.eq.ra;arith.diffintnullableDDE? Offset on declination between X-ray and optical positionsarcsecpos.eq.dec;arith.diffintnullableVmag? V magnitudemagphot.mag;em.opt.VfloatnullableB-V? B-V colour indexmagphot.color;em.opt.B;em.opt.VfloatnullableV-Ic? V-Ic colour indexmagphot.color;em.opt.V;em.opt.IfloatnullableMember[YN? ] Membershipmeta.code.membercharo_Vmag? Number of observation in V bandmeta.numberintnullableo_Bmag? Number of observation in B bandmeta.numberintnullableo_Icmag? Number of observation in Ic bandmeta.numberintnullableNameOptical counterpart name when available (1)meta.id.crosscharGSCGSC numbermeta.idcharNoteNotes (2)meta.notecharJ/AJ/110/1229/table5X-ray source list: Weaker possible sourceso_Icmag? Number of observation in Ic bandmeta.numberintnullablerecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintIDIdentification number [PSC95]meta.id;meta.mainintRA2000Right ascension (2000)pos.eq.ra;meta.mainDE2000Declination signpos.eq.dec;meta.mainOff-axisDistance off-axis from the center of the PSPC fieldarcmininstr.offsetfloatExpExposition timestime.duration;obs.exposureintCRateCount rates**-1phot.count;em.X-rayfloate_CRaterms uncertainty on CRates**-1stat.errorfloatS/NbBroadband (0.07-2.4keV) signal to noise ratiostat.snrfloatS/NhHardband (0.5-1.8keV) signal to noise ratiostat.snrfloatlogLxX-ray luminositylog(1e-07W)phys.luminosity;em.X-rayfloatl_HR[>= ] Limit flag on HRmeta.code.errorcharHR? Hardness ratiophot.flux;arith.ratiofloatnullableDRA? Offset on right ascension between X-ray and optical positionsarcsecpos.eq.ra;arith.diffintnullableDDE? Offset on declination between X-ray and optical positionsarcsecpos.eq.dec;arith.diffintnullableVmag? V magnitudemagphot.mag;em.opt.VfloatnullableB-V? B-V colour indexmagphot.color;em.opt.B;em.opt.VfloatnullableV-Ic? V-Ic colour indexmagphot.color;em.opt.V;em.opt.IfloatnullableMember[YN? ] Membershipmeta.code.membercharo_Vmag? Number of observation in V bandmeta.numberintnullableo_Bmag? Number of observation in B bandmeta.numberintnullableNameOptical counterpart name when available (1)meta.id.crosscharGSCGSC numbermeta.idcharNoteNotes (2)meta.notecharJ/AJ/110/1229/table8ESO CASPEC radial and rotational velocities (1994 April 21-25 UT)recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintStarStar namemeta.id;meta.maincharVmagV Magnitudemagphot.mag;em.opt.VfloatB-VB-V colour indexmagphot.color;em.opt.B;em.opt.VfloatV-IcV-Ic colour indexmagphot.color;em.opt.V;em.opt.IfloatRVRadial velocitykm/sphys.veloc;pos.heliocentricintu_RVUncertainty flag (:) on RVmeta.code.errorcharl_Vrot[<= ] Limit flag on Vrotmeta.code.errorcharVrot? Rotational velocitykm/sphys.veloc.rotatintnullableu_VrotUncertainty flag on Vrotmeta.code.errorcharMember[YN? ] Membermeta.code.membercharHJDHeliocentric Julian datedtime.epochdoubleNoteNotesmeta.notechar