J/A+A/682/A129ivo://CDS.VizieR/J/A+A/682/A129doi:10.26093/cds/vizier.36820129CDSMantovan G.Malavolta L.Desidera S.Zingales T.Borsato L.Piotto G.,Maggio A.Locci D.Polychroni D.Turrini D.Baratella M.Biazzo K.,Nardiello D.Stassun K.Nascimbeni V.Benatti S.Anna John A.,Watkins C.Bieryla A.Lissauer J.J.Twicken J.D.Lanza A.F.Winn J.N.,Messina S.Montalto M.Sozzetti A.Boffin H.Cheryasov D.Strakhov I.,Murgas F.D'Arpa M.Barkaoui K.Benni P.Bignamini A.Bonomo A.S.,Borsa F.Cabona L.Cameron A.C.Claudi R.Cochran W.Collins K.A.,Damasso M.Dong J.Endl M.Fukui A.Furesz G.Gandolfi D.Ghedina A.,Jenkins J.Kabath P.Latham D.W.Lorenzi V.Luque R.Maldonado J.,McLeod K.Molinaro M.Narita N.Nowak G.Orell-Miquel J.Palle E.,Parviainen H.Pedani M.Quinn S.N.Relles H.Rowden P.Scandariato G.,Schwarz R.Seager S.Shporer A.Vanderburg A.Wilson T.G.2024-11-06T20:06:50Z2024-02-13T12:07:20ZCDS support team

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

cds-question@unistra.frmultiple-starsexoplanetsradial-velocityvisible-astronomyShort-period giant planets (P<~10-days, Mp>0.1Mj) are frequently found to be solitary compared to other classes of exoplanets. Small inner companions to giant planets with P<~15-days are known only in five compact systems: WASP-47, Kepler-730, WASP-132, TOI-1130, and TOI-2000. Here, we report the confirmation of TOI-5398, the youngest compact multi-planet system composed of a hot sub-Neptune (TOI-5398 c, Pc=4.77271-days) orbiting interior to a short-period Saturn (TOI-5398 b, Pb=10.590547-days) planet, both transiting around a 650+/-150Myr G-type star. As part of the Global Architecture of Planetary System (GAPS) Young Object project, we confirmed and characterised this compact system, measuring the radius and mass of both planets, thus constraining their bulk composition. Using multidimensional Gaussian processes, we simultaneously modelled stellar activity and planetary signals from Transiting Exoplanet Survey Satellite (TESS) Sector 48light curve and our High Accuracy Radial velocity Planet Searcher (HARPS-N) radial velocity time series. We have confirmed the planetary nature of both planets, TOI-5398 b and TOI-5398 c, alongside a precise estimation of stellar parameters.Through the use of astrometric, photometric, and spectroscopic observations, our findings indicate that TOI-5398 is a young, active G dwarf star (650+/-150Myr), with a rotational period of Prot=7.34-days. The transit photometry and radial velocity measurements enabled us to measure both the radius and mass of planets b, Rb=10.30+/-0.40R_Earth_, Mb=58.7+/-5.7M_Earth_, and c, Rc=3.52+/-0.19R_Earth_, Mc=11.8+/-4.8M_Earth_. TESS observed TOI-5398 during sector 48 and no further observations are planned in the current Extended Mission, making our ground-based light curves crucial for ephemeris improvement. With a Transmission Spectroscopy Metric value around 300, TOI-5398 bis the most amenable warm giant (10<P<100-days) for JWST atmospheric characterisation.2024A&A...682A.129Mhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/682/A129CatalogResearchIsServedByTAP VizieR generic servicehttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/682/A129https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/682/A129http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/682/A129https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/682/A129https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/682/A129http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/682/A129GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapOpticaldefaultJ/A+A/682/A129/tablea1Spectroscopic time-seriesrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintBJDTime TDB (BJD-2400000)dtime.epochdoubleRVRadial velocitym/sphys.veloc;pos.heliocentricdoublee_RVRadial velocity uncertaintym/sstat.errorfloatBISCCF bisector spanm/sphys.velocdoublee_BISCCF bisector span uncertaintym/sstat.errorfloatlogR'HKlogR'_HK_ indexphot.flux;arith.ratiofloate_logR'HKlogR'_HK_ index uncertaintystat.errorfloatHaH{alpha} indexspect.indexfloate_HaH{alpha} index uncertaintystat.errorfloatFWHMCCF FWHMkm/sspect.line.widthfloate_FWHMCCF FWHM uncertaintykm/sstat.error;phys.angSizefloatEWCCF equivalent widthkm/sspect.line.eqWidthfloate_EWCCF equivalent width uncertaintykm/sstat.error;spect.line.eqWidthfloat