J/ApJ/916/66ivo://CDS.VizieR/J/ApJ/916/66doi:10.26093/cds/vizier.19160066CDSBrown T.M.Garcia R.A.Mathur S.Metcalfe T.S.Santos A.R.G.2023-02-27T11:54:55Z2023-01-24T14:58:59ZCDS support team

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

cds-question@unistra.fropen-star-clustersstellar-masseseffective-temperaturetwo-color-diagramsg-starsthe-sunvisible-astronomybroad-band-photometryinfrared-sourcesWe analyze space-based time-series photometry of Sun-like stars, mostly in the Pleiades, but also field stars and the Sun itself. We focus on timescales between roughly 1hr and 1day. In the corresponding frequency band these stars display brightness fluctuations with a decreasing power-law continuous spectrum. K2 and Kepler observations show that the rms flicker due to this mid-frequency continuum (MFC) can reach almost 1%, approaching the modulation amplitude from active regions. The MFC amplitude varies by a factor up to 40 among Pleiades members with similar Teff, depending mainly on the stellar Rossby number Ro. For Ro<=0.04, the mean amplitude is roughly constant at about 0.4%; at larger Ro the amplitude decreases rapidly, shrinking by about two orders of magnitude for Ro~1. Among stars, the MFC amplitude correlates poorly with that of modulation from rotating active regions. Among field stars observed for 3yr by Kepler, the quarterly average modulation amplitudes from active regions are much more time variable than the quarterly MFC amplitudes. We argue that the process causing the MFC is largely magnetic in nature and that its power-law spectrum comes from magnetic processes distinct from the star's global dynamo, with shorter timescales. By analogy with solar phenomena, we hypothesize that the MFC arises from a (sometimes energetic) variant of the solar magnetic network, perhaps combined with rotation-related changes in the morphology of supergranules.2021ApJ...916...66Bhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/916/66CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toIV/34 : K2 Ecliptic Plane Input Catalog (EPIC) (Huber+, 2017)I/345 : Gaia DR2 (Gaia Collaboration, 2018)III/284 : APOGEE-2 data from DR16 (Johnsson+, 2020)J/ApJS/224/2 : K2 EPIC stellar properties for 138600 targets (Huber+, 2016)J/MNRAS/408/475 : HATNet Pleiades Rotation Period Catalogue (Hartman+, 2010)J/ApJ/743/48 : Stars with rot. periods & X-ray luminosities (Wright+, 2011)J/A+A/572/A34 : Pulsating solar-like stars in Kepler (Garcia+, 2014)J/ApJS/211/24 : Rotation periods of Kepler MS stars (McQuillan+, 2014)J/MNRAS/456/2260 : K2 Variability Catalogue II (Armstrong+, 2016)J/ApJS/224/2 : K2 EPIC stellar properties for 138600 targets (Huber+, 2016)J/AJ/152/113 : Pleiades members with K2 LCs. I. Periods (Rebull+, 2016)J/AJ/152/114 : Pleiades members with K2 light curves. II. (Rebull+, 2016)J/AJ/152/115 : Pleiades members with K2 LCs. III. (Stauffer+, 2016)J/ApJ/835/172 : Kepler asteros. LEGACY sample. I. Oscillations (Lund+, 2017)J/ApJ/835/173 : Kepler asteroseismic LEGACY sample. II. (Silva Aguirre+, 2017)J/AJ/155/23 : Low-mass fast rotators in solar neighborhood (Saylor+, 2018)J/ApJS/237/17 : Temporal frequency shifts in 87 Kepler stars (Santos+, 2018)J/ApJS/243/28 : M-type star activities from LAMOST & Kepler (Lu+, 2019)J/ApJS/244/21 : Surface rot. & activity of Kepler stars. I. (Santos+, 2019)J/ApJS/247/28 : K2 star param. from Gaia & LAMOST (Hardegree-Ullman+, 2020)J/ApJS/251/23 : K2 GAP DR2: campaigns 4, 6 & 7 (Zinn+, 2020)J/A+A/635/A43 : Stellar rot. periods from K2 Campaigns 0-18 (Reinhold+, 2020)http://doi.org/10.17909/T9N889 : K2 Campaign 4 LCs on MAST.http://webda.physics.muni.cz/navigation.html : WEBDA databasehttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/916/66https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/916/66http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/916/66https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/916/66https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/916/66http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/916/66GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/ApJ/916/66/table1 (Star physical and fitted parameters)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJ/916/66/table1?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/916/66/table1?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/916/66/table1?GETtext/xml+votable180.050000true58.5783725.495260.0055555555555555565/115 118 6/319 329 405 408 437 453-454 457-459 466-467 470 478 480 484-486 496 14765 14771 14918 14932 14959-14960 15044 15062 15121 151313.322582951404819e-19 3.852589004194616e-19https://cdsarc.cds.unistra.fr/viz-bin/moc/J/ApJ/916/66?format=asciiOpticalInfrareddefaultJ/ApJ/916/66/table1Star physical and fitted parametersrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintCdncObserving cadence (5)meta.codecharlogsigH[1.82/4.65] log total harmonic RMS(10-6)stat.errorfloatlogsigC[1.19/3.86] log continuum RMS(10-6)stat.errorfloatSimbadNameSimbad column added by the CDSmeta.idcharnullableHz[25/10853]? Hertzsprung Catalog number (1)meta.id.crossintnullableRAJ2000? Right Ascension (J2000)degpos.eq.ra;meta.mainnullableDEJ2000? Declination (J2000)degpos.eq.dec;meta.mainnullableVmag[-1/17] Apparent Johnson V band magnitude from Rebull+ (2016, J/AJ/152/113)magphot.mag;em.opt.Vfloat(V-K)[0.99/5.11] The (V-K) color index from Rebull+ (2016, J/AJ/152/113)magphot.color;em.opt.V;em.IR.KfloatMass[0.26/1.63] Stellar masssolMassphys.massfloatTeff[3578/6711] Effective temperature from APOGEE (2)Kphys.temperature.effectiveintlogg[3.1/5.02] log surface gravity from APOGEE (2)log(cm.s**-2)phys.gravityfloatProt[0.23/42] Rotational period from Rebull+ (2016, J/AJ/152/113)dtime.periodfloatRo[0.005/2.15] Rossby number (Ro=Prot/{tau}_c_; with {tau}_c_, the turnover time for the stellar convection zone. See Section 4)stat.paramfloatBinBinarity flag (3)meta.codecharMemPleiades membership class (4)srccharalpha1[0.49/5.57] MFC power law indexmeta.code;spect.indexfloatR16Display data from Rebull+ 2016, J/AJ/152/113meta.ref.urlintnullableEPICDisplay data from the K2 EPIC cat. (IV/34) and Huber+ 2016 (J/ApJS/224/2)meta.ref.urlcharNameStar namemeta.id;meta.mainchar