J/A+A/686/A301ivo://CDS.VizieR/J/A+A/686/A301doi:10.26093/cds/vizier.36860301CDSKrenn A.F.Kubyshkina D.Fossati L.Egger J.A.Bonfanti A.Deline A.,Ehrenreich D.Beck M.Benz W.Cabrera J.Wilson T.G.Leleu A.,Sousa S.G.Adibekyan V.Correia A.C.M.Alibert Y.Delrez L.Lendl M.,Patel J.A.Venturini J.Alonso R.Anglada G.Asquier J.Barczy T.,Barrado Navascues D.Barros S.C.C.Baumjohann W.Beck T.Billot N.,Bonfils X.Borsato L.Brandeker A.Broeg C.Charnoz S.,Collier Cameron A.Csizmadia Sz.Cubillos P.E.Davies M.B.Deleuil M.,Demangeon O.D.S.Demory B.-O.Erikson A.Fortier A.Fridlund M.,Gandolfi D.Gillon M.Guedel M.Guenther M.N.Hasiba J.Heitzmann A.,Helling C.Hoyer S.Isaak K.G.Kiss L.L.Lam K.W.F.Laskar J.,Lecavelier des Etangs A.Lovis C.Magrin D.Maxted P.F.L.Mordasini C.,Nascimbeni V.Olofsson G.Ottensamer R.Pagano I.Palle E.Peter G.,Piotto G.Pollacco D.Queloz D.Ragazzoni R.Rando N.Rauer H.,Ribas I.Rieder M.Santos N.C.Scandariato G.Segransan D.Simon A.E.,Smith A.M.S.Stalport M.Steller M.Szabo Gy.M.Thomas N.Udry S.,Ulmer B.Van Grootel V.Villaver E.Viotto V.Walton N.A.Zingales T.2024-11-21T20:01:15Z2024-06-25T08:15:00ZCDS support team

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

cds-question@unistra.frmultiple-starsexoplanetsphotometryvisible-astronomyradial-velocityThe TOI-421 planetary system contains two sub-Neptune-type planets (Pb~5.2-days, T_eq,b_~900K, and Pc~16.1-days, T_eq,c_~650K) and is a prime target to study the formation and evolution of planets and their atmospheres. The inner planet is especially interesting as the existence of a hydrogen-dominated atmosphere at its orbital separation cannot be explained by current formation models without previous orbital migration. We aim to improve the system parameters to further use them to model the interior structure and simulate the atmospheric evolution of both planets, to finally gain insights into their formation and evolution. We also investigate the possibility of detecting transit timing variations (TTVs). We jointly analysed photometric data of three TESS sectors and six CHEOPS visits as well as 156 radial velocity data points to retrieve improved planetary parameters. We also searched for TTVs and modelled the interior structure of the planets. Finally, we simulated the evolution of the primordial H-He atmospheres of the planets using two different modelling frameworks. We determine the planetary radii and masses of TOI-421 b and c to be R_b_=2.64+/-0.08R_{Earth}_, M_b_=6.7+/-0.6M_{Earth}_, R_c_=5.09+/-0.07R_{Earth}_, and M_c_=14.1+/-1.4M_{Earth}_. Using these results we retrieved average planetary densities of rho_b_=0.37+/-0.05rho_{Earth}_ and rho_c_=0.107+/-0.012rho_{Earth}_. We do not detect any statistically significant TTV signals. Assuming the presence of a hydrogen-dominated atmosphere, the interior structure modelling results in both planets having extensive envelopes. While the modelling of the atmospheric evolution predicts for TOI-421 b to have lost any primordial atmosphere that it could have accreted at its current orbital position, TOI-421 c could have started out with an initial atmospheric mass fraction somewhere between 10 and 35%. We conclude that the low observed mean density of TOI-421b can only be explained by either a bias in the measured planetary parameters (e.g. driven by high-altitude clouds) and/or in the context of orbital migration. We also find that the results of atmospheric evolution models are strongly dependent on the employed planetary structure model.2024A&A...686A.301Khttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/686/A301CatalogResearchIsServedByTAP VizieR generic servicerelated-toJ/AJ/160/114 : Radial velocity monitoring of TOI-421 (Carleo+, 2020)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/686/A301https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/686/A301http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/686/A301https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/686/A301https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/686/A301http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/686/A301GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapOpticaldefaultJ/A+A/686/A301/cheops1Raw CHEOPS photometric time series with auxiliary detrending vectorsrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintTimeTime of mid-exposure (BJD)dtime.epochdoubleNFluxNormalised raw fluxphot.fluxdoublee_NFlux1-sigma uncertainty in NFluxstat.errordoubleRollSpacecraft roll angledeginstr.offsetdoubleCenXX-centroid positionpixpos.cartesian.x;instr.detdoubleCenYY-centroid positionpixpos.cartesian.y;instr.detdoubleBgFraction of flux in aperture from backgroundinstr.backgrounddoubleJ/A+A/686/A301/cheops2Detrended CHEOPS light curverecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintTimeTime of mid-exposure (BJD)dtime.epochdoubleNFluxdetNormalised detrended fluxphot.flux;arith.ratiodoublee_NFluxdet1-sigma uncertainty in NFluxdetstat.errordoubleJ/A+A/686/A301/tessDetrended TESS light curverecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintTimeTime of mid-exposure (BJD)dtime.epochdoubleNFluxdetNormalised detrended fluxphot.flux;arith.ratiodoublee_NFluxdet1-sigma uncertainty in NFluxdetstat.errordoubleJ/A+A/686/A301/harpsRaw and detrended HARPS radial velocitiesrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintTimeTime of mid-exposure (BJD)dtime.epochdoubleRVRadial Velocitykm/sphys.veloc;pos.heliocentricdoublee_RV1-sigma uncertainty in RVkm/sstat.errordoubleRVdetDetrended Radial Velocitykm/sphys.veloc;pos.heliocentricdoublee_RVdet1-sigma uncertainty in RVdetkm/sstat.errordoubleJ/A+A/686/A301/hiresRaw and detrended HIRES radial velocitiesrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintTimeTime of mid-exposure (BJD)dtime.epochdoubleRVRadial Velocitykm/sphys.veloc;pos.heliocentricdoublee_RV1-sigma uncertainty in RVkm/sstat.errordoubleRVdetDetrended Radial Velocitykm/sphys.veloc;pos.heliocentricdoublee_RVdet1-sigma uncertainty in RVdetkm/sstat.errordoubleJ/A+A/686/A301/fiesRaw and detrended FIES radial velocitiesrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintTimeTime of mid-exposure (BJD)dtime.epochdoubleRVRadial Velocitykm/sphys.veloc;pos.heliocentricdoublee_RV1-sigma uncertainty in RVkm/sstat.errordoubleRVdetDetrended Radial Velocitykm/sphys.veloc;pos.heliocentricdoublee_RVdet1-sigma uncertainty in RVdetkm/sstat.errordoubleJ/A+A/686/A301/pfsRaw and detrended PFS radial velocitiesrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintTimeTime of mid-exposure (BJD)dtime.epochdoubleRVRadial Velocitykm/sphys.veloc;pos.heliocentricdoublee_RV1-sigma uncertainty in RVkm/sstat.errordoubleRVdetDetrended Radial Velocitykm/sphys.veloc;pos.heliocentricdoublee_RVdet1-sigma uncertainty in RVdetkm/sstat.errordouble