J/A+A/480/495ivo://CDS.VizieR/J/A+A/480/495doi:10.26093/cds/vizier.34800495CDSMessina S.2017-10-11T05:13:27Z2008-05-01T15:33:01ZCDS support team

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

cds-question@unistra.frvariable-starsmultiple-starsvisible-astronomybroad-band-photometryThis is the first of a series of papers in which we present the results of a long-term photometric monitoring project carried out at Catania Astrophysical Observatory aimed at studying magnetic activity in late-type components of close binary systems, its dependence on global stellar parameters, and its evolution on different time scales from days to years. In this first paper, we present the complete observation dataset and new results of an investigation into the origin of brightness and color variations observed in the well-known magnetically active close binary stars: AR Psc, VY Ari, UX Ari, V711 Tau, EI Eri, V1149 Ori, DH Leo, HU Vir, RS CVn, V775 Her, AR Lac, SZ Psc, II Peg and BY Dra . About 38000 high-precision photoelectric nightly observations in the U, B and V filters are analysed. Correlation and regression analyses of the V magnitude vs. U-B and B-V color variations are carried out and a comparison with model variations for a grid of active region temperature and filling factor values is also performed. We find the existence of two different patterns of color variation. Eight stars in our sample: BY Dr, VY Ari, V775 Her, II Peg, V1149 Ori, HU Vir, EI Eri and DH Leo become redder when they become fainter, as is expected from the presence of active regions consisting of cool spots. The other six stars show the opposite behaviour, i.e. they become bluer when they become fainter. For V711 Tau this behaviour could be explained by the increased relative U- and B- flux contribution by the earlier-type component of the binary system when the cooler component becomes fainter. On the other hand, for AR Psc, UX Ari, RS CVn, SZ Psc and AR Lac the existence of hot photospheric faculae must be invoked. We also found that in single-lined and double-lined binary stars in which the fainter component is inactive or much less active the V magnitude is correlated to B-V and U-B color variations in more than 60% of observation seasons. The correlation is found in less than 40% of observation seasons when the fainter component has a non-negligible level of activity and/or hot faculae are present but they are either spatially or temporally uncorrelated to spots.2008A&A...480..495Mhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/480/495CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicehttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/480/495https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/480/495http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/480/495https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/480/495https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/480/495http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/480/495GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/480/495/table1 (Program stars)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/480/495/table1?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/480/495/table1?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/480/495/table1?GETtext/xml+votable180.050000true20.736257.4191670.0055555555555555566/845 924 4566 10474 13947 15243 18234 18889 20286 22707 22909 23191 25452 32211https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/480/495?format=asciiOpticaldefaultJ/A+A/480/495/table1Program starsHDHD numbermeta.idintrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintSeqSequential numbermeta.recordintTargetTarget's namemeta.id;meta.maincharprimaryRAJ2000Simbad right ascension (J2000)pos.eq.ra;meta.mainDEJ2000Simbad declination (J2000)pos.eq.dec;meta.mainSpTypeMK spectral typesrc.spTypecharPerPerioddtime.perioddoubleVmagBrightest V magnitudemagphot.mag;em.opt.VfloatVampV-band light curve amplitudemagphot.mag;em.opt.Vfloat<B-V>Mean B-V colour indexmagphot.color;em.opt.B;em.opt.Vfloat<U-B>Mean U-B colour indexmagphot.color;em.opt.U;em.opt.BfloatLc/LhV? Total flux ratio in the V band of the cool to the hot componentphot.flux;arith.ratiofloatnullablen_Lc/LhV[a] a if total flux of the hot to the cool componentmeta.notecharLc/LhB? Total flux ratio in the B band of the cool to the hot componentphot.flux;arith.ratiofloatnullablen_Lc/LhB[a] a if total flux of the hot to the cool componentmeta.notecharLc/LhU? Total flux ratio in the U band of the cool to the hot componentphot.flux;arith.ratiofloatnullablen_Lc/LhU[a] a if total flux of the hot to the cool componentmeta.notecharSimbadSimbad column added by the CDScharJ/A+A/480/495/table6Short timescale (rotation): average slopes of linear fits to B-V vs. V, U-B vs.V, and U-B vs. B-VrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintTargetTarget's namemeta.id;meta.maincharo_slopeBVNumber of light curves used in regression analysis B-V vs. Vmeta.numberintslopeBVAverage slope of the regression to B-V vs. Vstat.fit.paramfloate_slopeBVUncertainty of the average slope (B-V vs. V)stat.errorfloatslopeBVminMinimum value of average slope (B-V vs. V)stat.fit.paramfloatslopeBVmaxMaximum value of average slope (B-V vs. V)stat.fit.paramfloato_slopeUBNumber of light curves used in regression analysis U-B vs. Vmeta.numberintslopeUBAverage slope of the regression to U-B vs. Vstat.fit.paramfloate_slopeUBUncertainty of the average slope (U-B vs. V)stat.errorfloatslopeUBminMinimum value of average slope (U-B vs. V)stat.fit.paramfloatslopeUBmaxMaximum value of average slope (U-B vs. V)stat.fit.paramfloato_slopeUBVNumber of light curves used in regression analysis U-B vs. B-Vmeta.numberintslopeUBVAverage slope of the regression to U-B vs. B-Vstat.fit.paramfloate_slopeUBV? Uncertainty of the average slope (U-B vs. B-V)stat.errorfloatnullableslopeUBVmin? Minimum value of average slope (U-B vs. B-V)stat.fit.paramfloatnullableslopeUBVmax? Maximum value of average slope (U-B vs. B-V)stat.fit.paramfloatnullableJ/A+A/480/495/table7Long timescale: average slopes of linear fits to B-V vs. V, U-B vs.V, and U-B vs. B-VrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintTargetTarget's namemeta.id;meta.maincharParamParameters analysed for regression and correlation analysesstat.correlationo_slopeNumber of fitted datameta.numberintslopeSlope of linear regressionstat.fit.paramfloate_slopeSlope uncertaintystat.errorfloatrCorrelation coefficientstat.correlationfloatl_alphalimit flag on alphameta.code.error;pos.eq.racharalphaSignificance levelstat.fit.goodnessfloatalphal? Lower value of significance level if intervalstat.fit.goodnessfloatnullableJ/A+A/480/495/table4Summary of photometric observationsTargetTarget's namemeta.id;meta.maincharrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintEpochMean Epoch of light curveyrtime.epochfloatHJDmeanMean Heliocentric Julian Daydtime.epoch;stat.meandoubleHJDiniInitial Heliocentric Julian Daydtime.epoch;pos.heliocentricdoubleHJDendFinal Heliocentric Julian Daydtime.epoch;pos.heliocentricdoubleo_Vmag? Number of average data pointsmeta.numberintnullableVmagBrightest V-band light curve magnitudemagphot.mag;em.opt.VfloatVampV-band light curve amplitudemagphot.mag;em.opt.VfloatB-VMean B-V colour indexmagphot.color;em.opt.B;em.opt.VfloatU-B? Mean U-B colour indexmagphot.color;em.opt.U;em.opt.Bfloatnullablee_VmagV-band light curve standard deviationmagstat.error;phot.mag;em.opt.VfloateVmag(ck1-c)? V-band standard deviation of check minus comparison starmagstat.stdev;phot.mag;em.opt.VfloatnullableTelTelescope used (1)instr.setupcharJ/A+A/480/495/table5Summary of correlation and regression analysesrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintTargetTarget's namemeta.id;meta.maincharHJDmeanMean Heliocentric Julian Datedtime.epochdoubleo_bBVNumber of data points for regression analysis between B-V and Vmeta.numberintbBV? Slope of linear regression between B-V and Vstat.fit.paramfloatnullablerBV? Correlation coefficient between B-V and Vstat.correlationfloatnullablel_alphaBVLimit flag on alphaBVmeta.code.errorcharalphaBV? Significance level of rBVstat.fit.goodnessfloatnullablealphaBVl? Lower level od significance level of rBV if intervalstat.fit.goodnessfloatnullableo_bUB? Number of data points for regression analysis between U-B and Vmeta.numberintnullablebUB? Slope of linear regression between U-B and Vstat.fit.paramfloatnullablerUB? Correlation coefficient between U-B and Vstat.correlationfloatnullablel_alphaUBLimit flag on alphaUBmeta.code.errorcharalphaUB? Significance level of rUBstat.fit.goodnessfloatnullablealphaUBl? Lower value of significance level of rUB if intervalstat.fit.goodnessfloatnullableo_bUBV? Number of data points for regression analysis between U-B and B-Vmeta.numberintnullablebUBV? Slope of linear regression between U-B and B-Vstat.fit.paramfloatnullablerUBV? Correlation coefficient between U-B and B-Vstat.correlationfloatnullablel_alphaUBVLimit flag on alphaUBVmeta.code.errorcharalphaUBV? Significance level of rUBVstat.fit.goodnessfloatnullablealphaUBVl? Lower value of significance level of rUBV if intervalstat.fit.goodnessfloatnullable