J/A+A/678/A24ivo://CDS.VizieR/J/A+A/678/A24doi:10.26093/cds/vizier.36780024CDSReinhold T.Shapiro A.I.Solanki S.K. and Basri G.2024-11-06T20:06:10Z2023-09-29T08:05:01ZCDS support team

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

cds-question@unistra.frvariable-starsvisible-astronomyThe Kepler space telescope leaves a legacy of tens of thousands of stellar rotation period measurements. While many of these stars show strong periodicity, there exists an even bigger fraction of stars with irregular variability for which rotation periods are rarely visible or in most cases unknown. As a consequence, many stellar activity studies might be strongly biased toward the behavior of more active stars, for which rotation periods have been determined. To at least partially lift this bias, we apply a new method capable of determining rotation periods of stars with irregular light curve variability. This effort greatly increases the number of stars with well-determined periods, especially for stars with small variabilities similar to that of the Sun. To achieve this goal, we employ a novel method based on the Gradient of the Power Spectrum (GPS). The maximum of the gradient corresponds to the position of the inflection point (IP), i.e., the point where the curvature of the high-frequency tail of the power spectrum changes its sign. It was shown previously that the stellar rotation period Prot is linked to the inflection point period P_IP_) by the simple equation Prot=P_IP_/alpha, where alpha is a calibration factor. The GPS method is superior to classical methods (such as auto-correlation functions (ACF)) because it does not require a repeatable variability pattern in the time series, making it an ideal tool for detecting periods of stars with very short-lived spots. From the initial sample of 142168 stars with effective temperatures Teff<=6500K and logg>=4.0 in the Kepler archive, we could measure rotation periods for 67163 stars by combining the GPS and the ACF method. We further report the first determination of a rotation period for 20,397 stars. The GPS periods show good agreement with previous period measurements using classical methods, where these are available. Furthermore, we show that the scaling factor alpha increases for very cool stars with effective temperatures below 4000K, which we interpret as spots located at higher latitudes. We conclude that new techniques (such as the GPS method) must be applied to detect rotation periods of stars with small and more irregular variabilities. Ignoring these stars will distort the overall picture of stellar activity and, in particular, solar-stellar comparison studies.2023A&A...678A..24Rhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/678/A24CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toV/133 : Kepler Input Catalog (Kepler Mission Team, 2009)J/ApJS/211/24 : Rotation periods of Kepler MS stars (McQuillan+, 2014)J/ApJS/255/17 : Kepler stars surface rotation + activity. II. (Santos+, 2021)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/678/A24https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/678/A24http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/678/A24https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/678/A24https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/678/A24http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/678/A24GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/678/A24/tablec1 (Periods measured with the ACF and the GPS methods, including a final rotation period)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/678/A24/tablec1?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/678/A24/tablec1?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/678/A24/tablec1?GETtext/xml+votable180.050000true291.137636.57738110.0055555555555555564/922-923 933-935 944-946 5/3645-3647 3683 3704 3706 3729-3731 3760 3765 3788-3789 3792-3793 6/14559 14567 14573 14575 14577-14579 14730-14731 14738 14744 14746-14747 14749-14751 14792 14794-14795 14822 14828 14830-14831 14914-14915 15044-15045 15056-15057 15059 15160-15161 15176-15178 15200 15202 15232-15233https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/678/A24?format=asciiOpticaldefaultJ/A+A/678/A24/tablec1Periods measured with the ACF and the GPS methods, including a final rotation periodpointsPoint metricphot.mag;arith.zpfloatProtFinFinal rotation perioddtime.periodfloatMethodACF or GPS method usedmeta.notecharProtMcQ14McQuillan et al. (2014ApJS..211...24M, Cat. J/ApJS/211/24) rotation perioddtime.periodfloatProtS21Santos et al (2021ApJS..255...17S, Cat. J/ApJS/255/17) rotation perioddtime.periodfloat_RAPositions from KIC (Cat. V/133) catalog (right ascension part)degpos.eq.ra;meta.mainindexed_DEPositions from KIC (Cat. V/133) catalog (declination part)degpos.eq.dec;meta.mainindexedrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintKICKIC numbermeta.id;meta.mainintProtACFACF rotation perioddtime.periodfloatLPHLocal ACF peak heightphys.sizefloatProtGPSGPS rotation perioddtime.periodfloathIPInflection point peak heightstat.fit.paramfloatSNRSignal-to-noise ratiostat.snrfloatRvar6hMedian 6-hours smoothed variability range%stat.fit.paramfloatJ/A+A/678/A24/tableb1Up to 8 bad quarters removed from the analysisrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintKICKIC numbermeta.id;meta.mainintQuarter1Bad quarter removedobs.fieldintQuarter2? Bad quarter removedobs.fieldintnullableQuarter3? Bad quarter removedobs.fieldintnullableQuarter4? Bad quarter removedobs.fieldintnullableQuarter5? Bad quarter removedobs.fieldintnullableQuarter6? Bad quarter removedobs.fieldintnullableQuarter7? Bad quarter removedobs.fieldintnullableQuarter8? Bad quarter removedobs.fieldintnullable