J/A+A/668/A116ivo://CDS.VizieR/J/A+A/668/A116doi:10.26093/cds/vizier.36680116CDSGehan C.Gaulme P.Yu J.2024-11-06T20:01:31Z2022-12-09T08:05:47ZCDS support team

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

cds-question@unistra.frasteroseismologygiant-starsvisible-astronomyAccording to dynamo theory, stars with convective envelopes efficiently generate surface magnetic fields, which manifest as magnetic activity in the form of starspots, faculae, flares, when their rotation period is shorter than their convective turnover time. Most red giants, having undergone significant spin down while expanding, have slow rotation and no spots. However, based on a sample of about 4500 red giants observed by the NASA Kepler mission, a previous study showed that about 8% display spots, including about 15% that belong to close binary systems. Here, we shed light on a puzzling fact: for rotation periods less than 80 days, a red giant that belongs to a close binary system displays a photometric modulation about an order of magnitude larger than that of a single red giant with similar rotational period and physical properties. We investigate whether binarity leads to larger magnetic fields when tides lock systems, or if a different spot distribution on single versus close binary stars can explain this fact. For this, we measure the chromospheric emission in the CaII H and K lines of 3130 of the 4465 stars studied in a previous work thanks to the LAMOST survey. We show that red giants in a close-binary configuration with spin-orbit resonance display significantly larger chromospheric emission than single stars, suggesting that tidal locking leads to larger magnetic fields at a fixed rotational period. Beyond bringing interesting new observables to study the evolution of binary systems, this result could be used to distinguish single versus binary red giants in automatic pipelines based on machine learning.2022A&A...668A.116Ghttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/668/A116CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toV/133 : Kepler Input Catalog (Kepler Mission Team, 2009)J/A+A/639/A63 : Active red giants asteroseismic + rotation parametershttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/668/A116https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/668/A116http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/668/A116https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/668/A116https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/668/A116http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/668/A116GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/668/A116/table1 (S-index and associated uncertainties)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/668/A116/table1?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/668/A116/table1?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/668/A116/table1?GETtext/xml+votable180.050000true291.334220836.78663060.0055555555555555564/922-923 933-935 944-945 5/3645-3647 3683 3704 3706 3729-3731 3760 3784-3786 3788-3789 3792 6/14559 14567 14573 14575 14577-14579 14730-14731 14744 14746-14747 14749-14751 14792 14794-14795 14822 14828 14830-14831 14914-14915 15044-15045 15057 15059-15062 15148-15150 15160-15161 15172 15174 15176 15178 15200 15232https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/668/A116?format=asciiOpticaldefaultJ/A+A/668/A116/table1S-index and associated uncertaintiesrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintKICKIC numbermeta.id;meta.mainintSCaIIS-indexspect.indexfloate_SCaIIUncertainty on the S-indexstat.errorfloat_RAPositions from KIC (right ascension part)degpos.eq.ra;meta.main_DEPositions from KIC (declination part)degpos.eq.dec;meta.main