J/A+A/619/A73ivo://CDS.VizieR/J/A+A/619/A73doi:10.26093/cds/vizier.36190073CDSLorenzo-Oliveira D.Freitas F.Melendez J.Bedell M.Ramirez I.,Bean J.Asplund M.Spina L.Dreizler S.Alves-Brito A.Casagrande L.2025-04-17T20:00:44Z2018-11-08T08:09:18ZCDS support team

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

cds-question@unistra.frg-starsmagnetic-fieldseffective-temperaturemetallicitystellar-agesIt is well known that the magnetic activity of solar-type stars decreases with age, but it is widely debated in the literature whether there is a smooth decline or if there is an early sharp drop until 1-2Gyr that is followed by a relatively inactive constant phase. We revisited the activity-age relation using time-series observations of a large sample of solar twins whose precise isochronal ages and other important physical parameters have been determined. We measured the CaII H and K activity indices using 9000 HARPS spectra of 82 solar twins. In addition, the average solar activity was calculated through asteroids and Moon reflection spectra using the same instrumentation. Thus, we transformed our activity indices into the S Mount Wilson scale (S_MW_), recalibrated the Mount Wilson absolute flux and photospheric correction equations as a function of Te, and then computed an improved bolometric flux normalized activity index logR'_HK_(Teff) for the entire sample. New relations between activity and the age of solar twins were derived by assessing the chromospheric age-dating limits using logR'_HK_(Teff). We measured an average solar activity of S_MW_=0.1712+/-0.0017 during solar magnetic cycles 23-24 covered by HARPS observations, and we also inferred an average of S_MW_=0.1694+/-0.0025 for cycles 10-24, anchored on a sunspot number correlation of S index versus. We also found a simple relation between the average and the dispersion of the activity levels of solar twins. This enabled us to predict the stellar variability effects on the age-activity diagram, and consequently, to estimate the chromospheric age uncertainties that are due to the same phenomena. The age-activity relation is still statistically significant up to ages around 6-7Gyr, in agreement with previous works using open clusters and field stars with precise ages. Our research confirms that CaII H& K lines remain a useful chromospheric evolution tracer until stars reach ages of at least 6-7Gyr. We found evidence that for the most homogenous set of old stars, the chromospheric activity indices seem to continue to decrease after the solar age toward the end of the main sequence. Our results indicate that a significant part of the scatter observed in the age-activity relation of solar twins can be attributed to stellar cycle modulations eects. The Sun seems to have a normal activity level and variability for its age.2018A&A...619A..73Lhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/619/A73CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toIII/159 : Ca II H and K Measurements Made at MWO (Duncan+ 1991)J/AJ/111/439 : Chromospheric emission in late-type stars. (Henry+ 1996)J/ApJS/152/261 : Chromospheric Ca II emission in nearby stars (Wright+, 2004)J/MNRAS/372/163 : Activity indices for southern stars (Jenkins+, 2006)J/A+A/531/A8 : Activity indices & velocities for 890 stars (Jenkins+, 2011)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/619/A73https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/619/A73http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/619/A73https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/619/A73https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/619/A73http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/619/A73GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/619/A73/table2 (Parameters of all solar twins)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/619/A73/table2?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/619/A73/table2?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/619/A73/table2?GETtext/xml+votable180.050000true6.1772844-53.98399830.0055555555555555566/222 548 4128 4206 4313 4665 8244 8286 8614 8792 12312 12890 17301 17341 17572 17587 17721 17929 18209 18373 19491 21114 21177 21516 23429 23583 23661 23780 23873 25854 26160 26496 26888 27254 29422 29900 30878 30894 31029 31433 31945 33252 34983 35954 36453 36517 36590 36635 37515 37944 38279 38562 39557 39570 39576 39693 39801 39854 40105 40892 41935 42157 42228 42887 43105 43327 43845 43929 43989 44131 45182 46056 46193 46487 46681 46734 46933 47137 47194 48310 48607 49114https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/619/A73?format=asciidefaultJ/A+A/619/A73/table2Parameters of all solar twinsrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintHIPHIP numbermeta.id;meta.mainintn_HIP[*] Note on HIP (G1)meta.notecharVmagV magnitudemagphot.mag;em.opt.Vfloate_Vmag? rms uncertainty on Vmagmagstat.error;phot.magfloatnullableB-V? B-V colour indexmagphot.color;em.opt.B;em.opt.Vfloatnullablee_B-V? rms uncertainty on B-Vmagstat.error;phot.color;em.opt.BfloatnullableTeffEffective temperatureKphys.temperature.effectiveinte_Teff? rms uncertainty on TeffKstat.error;phys.temperature.effectiveintnullablelogg? Surface gravitylog(cm.s**-2)phys.gravityfloatnullablee_logg? rms uncertainty on logglog(cm.s**-2)stat.errorfloatnullable[Fe/H]? Metallicityphys.abund.Zfloatnullablee_[Fe/H]? rms uncertainty on [Fe/H]stat.error;phys.abund.FefloatnullableSMWMount Wildson CaII H and K activity S-index, S_MW_phot.flux;arith.ratiofloate_SMWrms uncertainty on SMWstat.errorfloatlogR'HK(Teff)logR'HK activity index (from Teff)phot.flux;arith.ratiofloate_logR'HK(Teff)rms uncertainty on logR'HK(Teff)stat.errorfloatAge? AgeGyrtime.agefloatnullableE_Age? Error on Age (upper limit)Gyrstat.error;stat.maxfloatnullablee_Age? Error on Age (lower limit)Gyrstat.error;time.agefloatnullableSimbadSimbad column added by the CDSmeta.ref.urlcharNObsNumber of observationsmeta.numberintTimeTime-spanyrtime.intervalfloat_RARight Ascension (J2000) from SIMBAD (not part of the original data)degpos.eq.ra;meta.main_DEDeclination (J2000) from SIMBAD (not part of the original data)degpos.eq.dec;meta.mainJ/A+A/619/A73/table1All the solar twins observed by HARPS, their respective programs and S values compiled from the literatureHIPHIP numbermeta.id;meta.mainintrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintn_HIP[*] Note on HIP (G1)meta.notecharESOESO programsmeta.id;obscharS? CaII H and K activity S-indexphot.flux;arith.ratiofloatnullablee_S? rms uncertainty on Sstat.errorfloatnullabler_SReference for S value (1)meta.ref;pos.framechar