J/A+A/676/A56ivo://CDS.VizieR/J/A+A/676/A56doi:10.26093/cds/vizier.36760056CDSBellotti S.Morin J.Lehmann L.T.Folsom C.P.Hussain G.A.J.Petit P.,Donati J-F.Lavail A.Carmona A.Martioli E.Romano Zaire B.,Alecian E.Moutou C.Fouque P.Alencar S.Artigau E.Boisse I.,Bouchy F.Cadieux C.Cloutier R.Cook N.J.Delfosse X.Doyon R.,Hebrard G.Kochukhov O.Wade G.A.2024-11-28T20:04:53Z2023-08-09T09:38:53ZCDS support team

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

cds-question@unistra.frm-starsmagnetic-fieldspolarimetryvisible-astronomyinfrared-astronomyOne clear manifestation of dynamo action on the Sun is the 22-yr magnetic cycle, exhibiting a polarity reversal and a periodic conversion between poloidal and toroidal fields. For M dwarfs, several authors claim evidence of activity cycles from photometry and spectroscopic indices analyses, but no clear polarity reversal has been identified from spectropolarimetric observations. These stars are excellent laboratories to investigate dynamo- powered magnetic fields under different stellar interior conditions, i.e. partly- or fully-convective. Our aim is to monitor the evolution of the large- scale field of AD Leo, which has shown hints of a secular evolution from past dedicated spectropolarimetric campaigns. This is of central interest to inform distinct dynamo theories, contextualise the evolution of the solar magnetic field, and explain the variety of magnetic field geometries observed in the past. We analysed near-infrared spectropolarimetric observations of the active M dwarf AD Leo taken with SPIRou between 2019 and 2020 and archival optical data collected with ESPaDOnS and Narval between 2006 and 2019. We searched for long-term variability in the longitudinal field, the width of unpolarised Stokes profiles, the unsigned magnetic flux derived from Zeeman broadening,and the geometry of the large-scale magnetic field using both Zeeman-Doppler Imaging and Principal Component Analysis. We found evidence of a long-term evolution of the magnetic field, featuring a decrease in axisymmetry (from 99 % to 60%). This is accompanied by a weakening of the longitudinal field (-300 to -50G) and a correlated increase in unsigned magnetic flux (2.8 to 3.6kG). Likewise, the width of the mean profile computed with selected near-infrared lines manifests a long-term evolution corresponding to field strength changes over the full time series, but does not exhibit modulation with the stellar rotation of AD Leo in individual epochs. The large-scale magnetic field of AD Leo manifested first hints of a polarity reversal in late 2020 in the form of a substantially increased dipole obliquity,while the topology remained predominantly poloidal and dipolar for 14 yr. This suggests that low-mass M dwarfs with a dipole dominated magnetic field can undergo magnetic cycles.2023A&A...676A..56Bhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/676/A56CatalogResearchIsServedByTAP VizieR generic servicerelated-toJ/MNRAS/390/567 : Magnetic field and velocity of mid M dwarfs (Morin+, 2008)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/676/A56https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/676/A56http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/676/A56https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/676/A56https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/676/A56http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/676/A56GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapOpticalInfrareddefaultJ/A+A/676/A56/tabled1List of ESPaDOnS 2019 observations for AD LeorecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintObsDate of observationstime.epochnullableNcycCycle number as computed with Eq. 1meta.id;meta.mainfloatTexpExposure time of polarimetric sequencestime.duration;obs.exposurecharS/NSignal-to-noise ratio of at 1650nmstat.snrintRMSRMS noise level of Stokes V (in 1e-4 unpolarised continuum unit)instr.det.noisefloatJ/A+A/676/A56/tabled2List of ESPaDOnS 2019 observations for AD LeoObsDate of observationstime.epochnullablerecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintNcycCycle number as computed with Eq. 1meta.id;meta.mainfloatTexpExposure time of polarimetric sequencestime.duration;obs.exposurecharS/NSignal-to-noise ratio of at 1650nmstat.snrintRMSRMS noise level of Stokes V (in 1e-4 unpolarised continuum unit)instr.det.noisefloatJ/A+A/676/A56/tabled3List of longitudinal field and magnetic flux measurements for AD LeorecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintHJDHeliocentric julian date of the observation (HJD-2450000)dtime.epochdoubleBlLongitudinal fieldGphys.magFieldfloate_BlFormal error bar on longitudinal fieldGstat.errorfloatSBf? Magnetic fluxkGphys.magFieldfloatnullableE_SBf? Upper error bar on magnetic fluxkGstat.error;stat.maxfloatnullablee_SBf? Lower error bar on magnetic fluxkGstat.errorfloatnullableInstInstrumentmeta.id;instrchar