J/A+AS/115/41ivo://CDS.VizieR/J/A+AS/115/41CDSCutispoto G.Tagliaferri G.Pallavicini R.Pasquini L.Rodono M.1997-12-09T18:02:31Z1997-12-09T19:02:26ZCDS support team

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

cds-question@unistra.frinfrared-photometryvisible-astronomyWide-band photometrylate-type-starsx-ray-sourcesWe present high-precision UBV(RI)_c_ photometry for a sample of active stars detected serendipitously by the EXOSAT satellite. Fourteen objects, out of 47 likely optical counterparts, turned out to be clearly variable, with periods in the range 1-8 days, including a newly discovered eclipsing binary. For most of them the optical variability is consistent with the presence of photospheric cool spots. We have used our multicolour photometry to estimate spectral classifications and distances. The derived distances indicate that some of the observed stars are previously unidentified nearby (d<=25pc) M dwarfs. When combined with the results of high resolution spectroscopy, our photometric observations allow us to investigate the stellar content of the selected X-ray sample. Young stars and RS CVn-type binaries appear to constitute a large fraction of the selected sample. For a description of the UBV and (RI)c photometric systems, see e.g. <http://obswww.unige.ch/gcpd/ph01.html> and <http://obswww.unige.ch/gcpd/ph54.html>.1996A&AS..115...41Chttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+AS/115/41CatalogResearchIsServedByTAP VizieR generic servicerelated-toJ/A+A/364/205 : UBVy photometry of cool stars. (Cutispoto+, 2000)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+AS/115/41https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+AS/115/41http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+AS/115/41https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+AS/115/41https://vizier.iucaa.in/viz-bin/votable?-source=J/A+AS/115/41http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+AS/115/41GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapX-rayOpticalInfrareddefaultJ/A+AS/115/41/table2Photometric data for the observed starsrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintIdIdentification numbermeta.id;meta.mainintNameEXOSAT name (Catalogue <VI/43>)meta.idcharObsSeasonCode for the observing season (1)meta.codecharn_ObsSeasonWhen "o": data from Paper I: Cutispoto G. et al 1991meta.notecharVmaxV magnitude at maximum luminositymagphot.mag;em.opt.VfloatU-B? U-B color indexmagphot.color;em.opt.U;em.opt.BfloatB-VB-V color indexmagphot.color;em.opt.B;em.opt.VfloatV-RcV-R_c_ color index (Cousins)magphot.color;em.opt.V;em.opt.RfloatV-IcV-I_c_ color index (Cousins)magphot.color;em.opt.V;em.opt.IfloatQualQuality of the datameta.notecharVarVariability flagmeta.code;src.varcharn_Var[?] Uncertainty on variability flagmeta.notecharJ/A+AS/115/41/table3Photometric dataDist? Distancepcpos.distanceintrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintIdIdentification numbermeta.idcharEXOSATEXOSAT namemeta.id;meta.maincharOtherOther catalogue numbermeta.idcharSpSpectral typesrc.spTypecharn_Dist[?] Uncertainty on distancemeta.notecharVarVariability flagmeta.code;src.varcharPeriod? Period of variabilitydtime.periodfloatn_Period[?] Uncertainty on period of variabilitymeta.notecharl_DeltaV[>] Limit flag on amplitude in V-bandmeta.code.errorcharDeltaV? Amplitude in the V-bandmagsrc.var.amplitudefloat