J/A+A/702/A69ivo://CDS.VizieR/J/A+A/702/A69doi:10.26093/cds/vizier/bc-ny/lgjCDSPersson C.M.Knudstrup E.Carleo I.Acuna-Aguirre L.Nowak G.,Muresan A.Jankowski D.Gozdziewski K.Garcia R.A.Mathur S.,Palakkatharappil D.B.Borg L.Mustill A.J.Barrena R.Fridlund M.,Gandolfi D.Hatzes A.P.Korth J.Luque R.Martin E.L.Masseron T.,Morello G.Murgas F.Orell-Miquel J.Palle E.Albrecht S.H.Bieryla A.,Cochran W.D.Crossfield I.J.M.Deeg H.J.Furlan E.Guenther E.W.,Howell S.B.Isaacson H.Lam K.W.F.Livingston J.Matson R.A.,Matthews E.C.Redfield S.Schlieder Jo.E.Seager S.Smith Al.M.S.,Stassun K.G.Twicken J.D.Van Eylen V.Watkins C.N.Weiss L.M.2026-08-03T06:58:36Z2025-10-07T11:44:43ZCDS support team

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

cds-question@unistra.frmultiple-starsexoplanetsradial-velocityvisible-astronomyWe present the detection and characterisation of the TOI-1438 multi-planet system discovered by the Transiting Exoplanet Survey Satellite (TESS). To confirm the planetary nature of the candidates and determine their masses, we collected a series of follow-up observations including high-spectral resolution observations with HARPS-N and HIRES over a period of five years. Our combined modelling shows that the K0V star hosts two transiting sub-Neptunes with Rb=3.04+/-0.19R_{Earth}_, Rc=2.75+/-0.14R_{Earth}_, Mb=9.4+/-1.8M_{Earth}_, and Mc=10.6+/-2.1M_{Earth}_. The orbital periods of planets b and c are 5.1 and 9.4 days, respectively, corresponding to instellations of 145+/-10F_{Earth}_ and 65+/-4F_{Earth}_. The bulk densities are 1.8+/-0.5 and 2.9+/-0.7g/cm^3^, respectively, suggesting a volatile-rich interior composition. We computed a set of planet interior structure models. Planet b presents a high-metallicity envelope that can accommodate up to 2.5% in H/He in mass, while planet c cannot have more than 0.2% as H/He in mass. For any composition of the core considered (Fe-rock or ice-rock), both planets would require a volatile-rich envelope. In addition to the two planets, the radial velocity (RV) data clearly reveal a third signal, likely coming from a non-transiting planet, with an orbital period of 7.6^+1.6^_-2.4_ years and a radial velocity semi-amplitude of 35^+3^_-5_m/s. Our best fit model finds a minimum mass of 2.1+/-0.3M_J_ and an eccentricity of 0.25^+0.08^_-0.11_. However, several RV activity indicators also show strong signals at similar periods, suggesting this signal might (partly) originate from stellar activity. More data over a longer period of time are needed to conclusively determine the nature of this signal. If it is confirmed as a triple-planet system, TOI-1438 would be one of the few detected systems to date characterised by an architecture with two small, short-period planets and one massive, long-period planet, where the inner and outer systems are separated by an orbital period ratio of the order of a few hundred.2025A&A...702A..69Phttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/702/A69CatalogResearchIsServedByTAP VizieR generic servicehttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/702/A69https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/702/A69http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/702/A69https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/702/A69https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/702/A69http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/702/A69GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapOpticaldefaultJ/A+A/702/A69/tablea1RVs with HARPS-N, DRS pipelinerecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintTimeBarycentric Julian date, TBD (BJD-2457000)dtime.epochdoubleRVRadial velocitym/sphys.veloc;pos.heliocentricdoublee_RVRV errorm/sstat.errorfloatBISActivity indicator, Bisector span of the CCFm/sphys.velocfloate_BISBIS errorm/sstat.errorfloatFWHMActivity indicator, FWHM of the CCFkm/sspect.line.widthfloatContrastActivity indicator, contrast of the CCF%phot.flux;arith.ratiofloatlogR'HKActivity indicator, Mount Wilson logRHK indexphot.flux;arith.ratiofloate_logR'HKlog R'_HK_ errorstat.errorfloatSNRSignal to noise at 550nmstat.snrfloatExpTimeExposure timestime.duration;obs.exposurefloatJ/A+A/702/A69/tablea2RVs with HARPS-N, Serval pipelinerecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintTimeBarycentric Julian date, TBD (BJD-2457000)dtime.epochdoubleRVRadial velocitym/sphys.veloc;pos.heliocentricfloate_RVRV errorm/sstat.errorfloatCRXActivity indicator, chromatic index (in m/s/Np unit)m/sspect.indexfloate_CRXCRX error (in m/s/Np unit)m/sstat.errorfloatdlWActivity indicator, differential linewidthm**2.s**-2spect.line.widthfloate_dlWdlW errorm**2.s**-2stat.errorfloatHalphaActivity indicator, Halpha line indexspect.index;em.line.Halphafloate_HalphaHalpha errorstat.error;spect.linefloatNaD1Activity indicator, Na D1 indexspect.indexfloate_NaD1NaD1 errorstat.errorfloatNaD2Activity indicator, Na D2 indexspect.indexfloate_NaD2NaD2 errorstat.errorfloatSNRSignal to noise at 600nmstat.snrfloatExpTimeExposure timestime.duration;obs.exposurefloatJ/A+A/702/A69/tablea3RVs with HIRESrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintTimeBarycentric Julian date, TBD (BJD-2457000)dtime.epochdoubleRVRadial velocitym/sphys.veloc;pos.heliocentricdoublee_RVRV errorm/sstat.errordoubleSindexActivity indicator, S-indexspect.indexfloate_SindexSindex errorstat.errorfloat