J/A+A/700/A216ivo://CDS.VizieR/J/A+A/700/A216doi:10.26093/cds/vizier/bc-nw/lcbgCDSGeraldia-Gonzalez S.Orell-Miquel J.Palle E.Murgas F.Lacedelli G.,Bejar V.J.S.Caballero J.A.Duque-Arribas C.Lillo-Box J.Montes D.,Morello G.Nagel E.Schweitzer A.Tabernero H.M.Calatayud-Borras Y.,Cifuentes C.Fernandez-Rodriguez G.Fukui A.de Leon J.Lodieu N.,Luque R.Mori M.Narita N.Parviainen H.Poultourtzidis E.Reiners A.,Ribas I.Schlecker M.Seager S.Stassun K.G.Trifonov T.,Vanaverbeke S.Winn J.N.2026-08-03T06:56:28Z2025-08-20T08:17:08ZCDS support team

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

cds-question@unistra.frmultiple-starsexoplanetsradial-velocityphotometryvisible-astronomyspectroscopyThe Transiting Exoplanet Survey Satellite (TESS) discovers several new planet candidates that need to be confirmed and characterized with ground-based observations. This is the case for Ross 176, a late K-type star that hosts a promising water world candidate planet. The star has a radius of R_star_=0.569+/-0.020R_{sun}_ and a mass of M_star_=0.577+/-0.024M_{sun}_. Here, we constrain the planetary mass using spectroscopic data from CARMENES, an instrument that has already played a major role in confirming the planetary nature of the transit signal detected by TESS. We make use of Gaussian Processes (GP) to improve the analysis because the host star has a relatively strong activity that affects the radial-velocity dataset. In addition, we applied a GP to the TESS light curves to reduce the correlated-noise in the detrended dataset. The stellar activity indicators show a strong signal related to the star rotation period of ~32-days. This stellar activity signal was also confirmed on the TESS light curves. Ross 176b is an inner hot transiting planet with a low eccentricity orbit of ecc=0.25+/-0.04, an orbital period of P~5-days, and an equilibrium temperature of T_eq_~682K. With a radius of R_p_=1.84+/-0.08R_{Earth}_ (4% precision), a mass of M_p_=4.57^+0.89^_-0.93_M_{Earth}_ (20% precision), and a mean density of rho_p_=4.03^+0.49^_-0.81_g/cm^3^, the composition of Ross 176b is consistent with a water world scenario. Moreover, Ross 176b is a promising target for atmospheric characterization, which could lead to more information on the existence, formation and composition of water worlds. This detection increases the sample of planets orbiting K-type stars, which is valuable to investigate the presence of the small planet radius valley around this type of star. This study also showcases the efficiency of the dual detection between space- and ground-based telescopes to confirm new planets.2025A&A...700A.216Ghttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/700/A216CatalogResearchIsServedByTAP VizieR generic servicehttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/700/A216https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/700/A216http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/700/A216https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/700/A216https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/700/A216http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/700/A216GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapOpticaldefaultJ/A+A/700/A216/muscat2MuSCAT2 photometry datarecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintBJDBarycentric Julian datedtime.epochdoubleFgRelative flux for the g bandphot.flux.density;em.opt.Bdoublee_FgRelative flux error for the g bandstat.errordoubleFrRelative flux for the r bandphot.flux.density;em.opt.Rdoublee_FrRelative flux error for the r bandstat.errordoubleFiRelative flux for the i bandphot.flux.density;em.opt.Idoublee_FiRelative flux error for the i bandstat.errordoubleFzsRelative flux for the zs bandphot.flux.density;em.opt.Idoublee_FzsRelative flux error for the zs bandstat.errordoubleJ/A+A/700/A216/rvCARMENES (VIS) radial velocity measurementsrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintBJDBarycentric Julian datedtime.epochdoubleRVRadial velocity (VIS channel)m/sphys.veloc;pos.heliocentricdoublee_RVRadial velocity error (VIS channel)m/sstat.errordoubleJ/A+A/700/A216/actindSERVAL spectral line activity indicesrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintBJDBarycentric Julian datedtime.epochdoubleHalphaH{alpha} indexspect.indexdoublee_HalphaH{alpha} index uncertaintystat.error;spect.linedoubleNaD1Na D1 indexspect.indexdoublee_NaD1Na D1 index uncertaintystat.errordoubleNaD2Na D2 indexspect.indexdoublee_NaD2Na D2 index uncertaintystat.errordoubleCaIRT1Ca IRT 1 indexspect.indexdoublee_CaIRT1Ca IRT 1 index uncertaintystat.errordoubleCaIRT2Ca IRT 2 indexspect.indexdoublee_CaIRT2Ca IRT 2 index uncertaintystat.errordoubleCaIRT3Ca IRT 3 indexspect.indexdoublee_CaIRT3Ca IRT 3 index uncertaintystat.errordoubleCRXChromatic index (in m/s/Np)spect.indexdoublee_CRXChromatic index uncertainty(in m/s/Np)stat.errordoubledLWDifferential line widthm**2.s**-2spect.line.width;arith.diffdoublee_dLWDifferential line width uncertaintym**2.s**-2stat.errordouble