J/A+A/711/A261ivo://CDS.VizieR/J/A+A/711/A261CDSSchmitt J.H.M.M.Schroeder K.-P.Mittag M.Hempelmann A.,Gonzalez-Perez J.N.Jack D.2026-07-21T08:07:32Z2026-07-21T08:59:33ZCDS support team

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

cds-question@unistra.frg-starsspectroscopyvisible-astronomyThe combined time series of the consistently calibrated chromospheric activity indicator, the S-index - derived from Mount Wilson and TIGRE data - now spans more than five decades of monitoring observations of the Sun and of more than one hundred solar-like stars. For the first time, these data allow us to probe the long-term stability of solar-type magnetic cycles as well as their possible transition into other behavioral forms of stellar activity in the time domain. Such variability studies are an important input for solarstellar connection research and for our empirical understanding of the long-term perspective of solar activity as well as of a wider empirical picture of the coevolution of magnetic activity with stellar structure. We here present and discuss a representative selection of cool main-sequence stars, for which such data are available. The excellent quality of our TIGRE data now more than doubles the number of known cyclic stars. Grading them (i.e., excellent, good, fair, and poor) and putting them into an evolutionary perspective, we find that stars more active than the Sun are also more likely to show cyclic variability than stars below solar activity. Furthermore, more active stars tend to have more regular cycles, while the solar mean S-value fits the lower end of the S-index range found for cyclic stars. This is consistent with the occurrence of solar Maunder minima episodes, hinting at a sometimes already unstable solar cycle. We find eighteen stars with even lower activity and lower variability than the Sun, which provide a preview into the latter,s distant future. For half of these stars, we can use sensitive X-ray observations to complement our chromospheric data and to explore the lower end of stellar activity also from a coronal perspective. These so-called "Maunder minimum candidate stars" exhibit what we refer to as "remnant activity", which expresses itself in a minimal coronal flux and a minimal S-value, above which only rather small variations occur. Using accurate Gaia DR3 distances allows us to place our sample stars into an Hertzsprung-Russell diagram (HRD), which demonstrates that active cyclic stars and inactive noncyclic stars populate rather different regions in the HRD.2026A&A...711A.261Shttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/711/A261CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicehttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/711/A261https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/711/A261http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/711/A261https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/711/A261https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/711/A261http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/711/A261GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/711/A261/stars (List of studied stars)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/711/A261/stars?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/711/A261/stars?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/711/A261/stars?GETtext/xml+votable180.050000true172.9372514.36450.0055555555555555566/137 254 684 1247 2650 3639 4468 4591 5013 5074 7763 8790 9072 10375 11128 11856 12944 13301 14522 16069 17137 18139 19912 20278 21177 22708 22818 22841 23230 23342 24151 25444 27006 27973 28180 28605 28664 29196 30176 30529 30576 30965 31072 31101 31130 31132 31416 31751 32552 32757 36697 40823 40932https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/711/A261?format=asciiOpticaldefaultJ/A+A/711/A261/starsList of studied starsrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintNameHD namemeta.id;meta.maincharRAJ2000Simbad right ascension (J2000)pos.eq.ra;meta.mainDEJ2000Simbad declination (J2000)pos.eq.dec;meta.mainplotShow the S-index curvemeta.ref.urlcharSimbadSimbad column added by the CDSmeta.ref.urlcharJ/A+A/711/A261/tableIndex measurements, phased and unphasedrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintNameHD Namemeta.id;meta.maincharPerPerioddtime.periodfloatCycleCycle typemeta.notecharDateDateyrtime.epochdoubleindexedPhasePhasetime.phasedoubleS-indexS-indexphot.flux;arith.ratiodoubleInstInstrument (MW for Mount Wilson, TIG for TIGRE)meta.id;instrchar