J/A+A/710/A275ivo://CDS.VizieR/J/A+A/710/A275CDSGrouffal S.Santerne A.Dumusque X.Akinsanmi B.Guillot T.,Hara N.C.Leleu A.Malavolta L.Saillenfest M.Armstrong D.J.,Barros S.C.C.Bayliss D.Bonomo A.S.Brown D.J.A.Collier Cameron A.,Cretignier M.Crossfield I.J.M.Dai F.Damasso M.Demangeon O.,Figueira P.Leonardi P.Martinez Fiorenzano A.F.Lopez-Morales M.,Molinari E.Mortier A.Nielsen L.D.Osborn H.P.Petigura E.Rice K.,Santos N.C.Sozzetti A.Sulis S.Udry S.Watson C.2026-06-23T08:42:20Z2026-06-23T09:41:40ZCDS support team

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

cds-question@unistra.frmultiple-starsexoplanetsradial-velocityvisible-astronomyMulti-planetary systems provide key constraints on planet formation and evolution, as their architecture encodes the dynamical history of planets formed within a common protoplanetary disk. However, the current population remains strongly biased toward compact, short-period systems, and only a limited number of such systems with measured masses and radii are known. HIP 41378 is an exceptional system hosting five transiting planets with orbital periods up to 1.5 years, including an ultra-low density planet HIP 41378 f. The outer transiting planets d and e remained poorly constrained with unknown periods and masses, leaving the system architecture only partially characterised. We present long-term monitoring of this target with high-precision radial-velocity (RV) instruments (HARPS, HARPS-N, HIRES, and ESPRESSO) and space-based photometry spanning 2015-2024. We detect RV signals for all the planets, confirming their orbital periods and constraining their masses. In particular, the RV data strongly favour an orbital period of Pd=278-days for planet d and refine the orbital period of planet e to Pe=393^+3^_-5_days. We measure a new mass of Mf=25+/-5M_{Earth}_ for HIP 41378 f, confirming its super-puff nature with a bulk density of {rho}f=0.166^+0.033^_-0.036_g/cm^3^. We also confirm the planetary nature of HIP 41378 g, a non-transiting planet with a 63-day period, and determine its minimum mass. In addition, the RVs reveal a long-period signal, with P=2602^+468^_-433_days, which we attribute to the candidate planet HIP 41378 h, although a stellar magnetic cycle cannot be excluded. Finally, we investigate the system's dynamical architecture and resonant structure, assess its completeness by constraining additional undetected planets, and discuss the implications for the origin and internal structure of the remarkable planet HIP 41378 f.2026A&A...710A.275Ghttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/710/A275CatalogResearchIsServedByTAP VizieR generic servicehttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/710/A275https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/710/A275http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/710/A275https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/710/A275https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/710/A275http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/710/A275GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapOpticaldefaultJ/A+A/710/A275/harpnHIP 41378 HARPN radial velocitiesrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintJDReduced Julian date (JD-2400000)dtime.epochdoubleRVRadial velocitym/sphys.veloc;pos.heliocentricdoublee_RVRadial velocity errorm/sstat.errordoubleJ/A+A/710/A275/harps15HIP 41378 HARPS15 radial velocitiesrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintJDReduced Julian date (JD-2400000)dtime.epochdoubleRVRadial velocitym/sphys.veloc;pos.heliocentricdoublee_RVRadial velocity errorm/sstat.errordoubleJ/A+A/710/A275/espr19HIP 41378 ESPR19 radial velocitiesrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintJDReduced Julian date (JD-2400000)dtime.epochdoubleRVRadial velocitym/sphys.veloc;pos.heliocentricdoublee_RVRadial velocity errorm/sstat.errordoubleJ/A+A/710/A275/hiresHIP 41378 HIRES radial velocitiesrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintJDReduced Julian date (JD-2400000)dtime.epochdoubleRVRelative radial velocitym/sphys.veloc;pos.heliocentricfloate_RVRelative radial velocity errorm/sstat.errorfloat