J/A+A/710/A407ivo://CDS.VizieR/J/A+A/710/A407CDSGonzalez-Ramirez L.Barrado D.Olivares J.Berihuete A.Sarro L.M.,Palmero F.J.2026-07-01T08:03:22Z2026-07-01T08:59:01ZCDS support team

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

cds-question@unistra.fropen-star-clustersradial-velocityinfrared-photometryvisible-astronomyeffective-temperaturestellar-distanceEstablishing a self-consistent age scale for stellar populations requires physically well-calibrated chronometers. Among these, lithium-based diagnostics, particularly the lithium depletion boundary (LDB), provide one of the most robust age constraints for stellar populations in the low-mass regime. However, their application is limited by heterogeneous temperature scales and astrophysical dispersion, especially among FGK stars, where rotation can significantly affect lithium abundances. As a first step towards a self-consistent age scale, our aim has been to formulate CHRONOS, the first version of a Bayesian hierarchical lithium-based age-dating model combined with a neural network trained on stellar evolutionary models. We implemented a Bayesian hierarchical model that jointly infers stellar effective temperatures, lithium abundances, and the global age of a stellar association. The theoretical LDB is provided by a pre-trained multilayer perceptron based on BT-Settl evolutionary models. The model incorporates a temperature-dependent transition between fully convective ultra-cool dwarfs (UCDs) and FGKM dwarf stars, together with a two-component FGK mixture to account for rotation-induced lithium enhancement. We applied the method to the Pleiades cluster and performed a validation using synthetic datasets. For the Pleiades cluster, CHRONOS yields a posterior age distribution centred at Age=124.53_-2.70_^+3.34^Myr, consistent with classical LDB estimates, while simultaneously constraining both global and stellar-level rotation parameters. This work demonstrates that lithium-based stellar chronology can be recast as a coherent hierarchical inference problem, providing a flexible and statistically robust framework for making age determinations for young (1-600Myr) stellar populations.2026A&A...710A.407Ghttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/710/A407CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toI/355 : Gaia DR3 Part 1. Main source (Gaia Collaboration, 2022)J/A+A/577/A148 : The Seven Sisters DANCe. I. Pleiades (Bouy+, 2015)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/710/A407https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/710/A407http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/710/A407https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/710/A407https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/710/A407http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/710/A407GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/710/A407/pleiades (Pleiades members used in Chronos analysis)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/710/A407/pleiades?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/710/A407/pleiades?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/710/A407/pleiades?GETtext/xml+votable180.050000true53.3080066176223.006232598560.0055555555555555565/115 118 6/382 454-455 457 466-467 480 484-486 496 498 5048.157980699529898e-21 5.101838343667421e-19https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/710/A407?format=asciiOpticalInfrareddefaultJ/A+A/710/A407/pleiadesPleiades members used in Chronos analysisrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintGaiaDR3Gaia DR3 source identifier (1)meta.idGLONGalactic longitudedegpos.galactic.lone_W4mag? Uncertainty on W4magmagstat.error;phot.magdoublenullablel_EWLiLimit flag on EWLimeta.code.errorcharr_EWLiReference for EWLi (3)meta.ref;pos.framecharEWLiEquivalent width of LiI 6708 Angstrom line0.1pmspect.line.eqWidthfloate_EWLiUncertainty on EWLi0.1pmstat.errordoubleTeffEffective temperatureKphys.temperature.effectivefloate_TeffUncertainty on TeffKstat.error;phys.temperature.effectivefloatLbolBolometric luminositylog(solLum)phys.luminositydoublee_LbolUncertainty on Lbollog(solLum)stat.errordoubleloggSurface gravitylog(cm.s**-2)phys.gravitydoubleALiLithium abundancephys.abunddoubleSimbadNameSimbad column added by the CDSmeta.idcharnullable_RA.icrsRight ascension (ICRS) at Epoch=J2000, proper motions taken into accountdegpos.eq.raindexed_DE.icrsDeclination (ICRS) at Epoch=J2000, proper motions taken into accountdegpos.eq.decindexedGLATGalactic latitudedegpos.galactic.latdoubleRA_ICRSRight ascension (ICRS) at Ep=2016.0degpos.eq.ra;meta.maine_RA_ICRSUncertainty on RAmasstat.error;pos.eq.radoubleDE_ICRSDeclination (ICRS) at Ep=2016.0degpos.eq.dec;meta.maine_DE_ICRSUncertainty on DEmasstat.error;pos.eq.decdoubleplx? Parallax (Gaia DR3)maspos.parallax.trigfloatnullablee_plx? Uncertainty on parallaxmasstat.error;pos.parallaxfloatnullablepmRAProper motion RA* (Gaia DR3)mas/yrpos.pm;pos.eq.rafloate_pmRAUncertainty on pmRAmas/yrstat.error;pos.pm;pos.eq.rafloatpmDEProper motion Dec (Gaia DR3)mas/yrpos.pm;pos.eq.decfloate_pmDEUncertainty on pmDEmas/yrstat.error;pos.pm;pos.eq.decfloatSpTypeSpectral type (MK system)src.spTypecharRV? Radial velocitykm/sphys.veloc;pos.heliocentricfloatnullablee_RV? Uncertainty on RVkm/sstat.errorfloatnullabler_RVReference for RV (2)meta.ref;pos.framecharruwe? Gaia DR3 RUWEstat.errordoublenullableGmag? Gaia G magnitudemagphot.mag;em.optdoublenullablee_Gmag? Uncertainty on Gmagmagstat.error;phot.magdoublenullableBPmag? Gaia BP magnitudemagphot.mag;em.opt.Bdoublenullablee_BPmag? Uncertainty on BPmagmagstat.error;phot.magdoublenullableRPmag? Gaia RP magnitudemagphot.mag;em.opt.Rdoublenullablee_RPmag? Uncertainty on RPmagmagstat.error;phot.magdoublenullableJmag2MASS J magnitudemagphot.mag;em.IR.Jdoublee_JmagUncertainty on Jmagmagstat.error;phot.magdoubleHmag2MASS H magnitudemagphot.mag;em.IR.Hdoublee_HmagUncertainty on Hmagmagstat.error;phot.magdoubleKmag2MASS Ks magnitudemagphot.mag;em.IR.Kdoublee_KmagUncertainty on Kmagmagstat.error;phot.magdoublegmag? g-band magnitudemagphot.mag;em.opt.Bfloatnullablee_gmag? Uncertainty on gmagmagstat.error;phot.magdoublenullablermag? r-band magnitudemagphot.mag;em.opt.Rfloatnullablee_rmag? Uncertainty on rmagmagstat.error;phot.magdoublenullableimag? i-band magnitudemagphot.mag;em.opt.Idoublenullablee_imag? Uncertainty on imagmagstat.error;phot.magdoublenullableYmag? Y-band magnitudemagphot.mag;em.IR.Jdoublenullablee_Ymag? Uncertainty on Ymagmagstat.error;phot.magdoublenullableumag? u-band magnitudemagphot.mag;em.opt.Ufloatnullablee_umag? Uncertainty on umagmagstat.error;phot.magdoublenullableBTmag? Tycho BT magnitudemagphot.mag;em.opt.Bfloatnullablee_BTmag? Uncertainty on BTmagmagstat.error;phot.magdoublenullableVTmag? Tycho VT magnitudemagphot.mag;em.opt.Vfloatnullablee_VTmag? Uncertainty on VTmagmagstat.error;phot.magdoublenullableW1mag? WISE W1 magnitudemagphot.mag;em.IR.3-4umdoublenullablee_W1mag? Uncertainty on W1magmagstat.error;phot.magdoublenullableW2mag? WISE W2 magnitudemagphot.mag;em.IR.4-8umdoublenullablee_W2mag? Uncertainty on W2magmagstat.error;phot.magdoublenullableW3mag? WISE W3 magnitudemagphot.flux.density;em.IR.8-15umdoublenullablee_W3mag? Uncertainty on W3magmagstat.error;phot.magdoublenullableW4mag? WISE W4 magnitudemagphot.flux.density;em.IR.15-30umdoublenullablee_ALiUncertainty on AListat.errordoubleDistDistance (4)pcpos.distancedoublevsini? Projected rotational velocitykm/sphys.veloc.rotatfloatnullabler_vsiniReference for vsini (5)meta.refcharPmbMembership probability (Sarro et al., 2014A&A...563A..45S)stat.probabilityfloatNameCl* Melotte 22 identifiermeta.id;meta.maincharDANCeDANCe I identifier (Bouy et al., 2015A&A...577A.148B, Cat. J/A+A/577/A148)meta.idchar