J/A+A/695/A62ivo://CDS.VizieR/J/A+A/695/A62doi:10.26093/cds/vizier/bc-nq/lgcCDSStefanov A.K.Suarez Mascareno A.Gonzalez Hernandez J.I.Nari N.,Rebolo R.Affer L.Micela G.Ribas I.Sozzetti A.Perger M.,Pinamonti M.Damasso M.Maldonado J.Gonzalez Alvarez E.Scandariato G.2026-07-03T06:36:45Z2025-05-12T08:41:01ZCDS support team

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

cds-question@unistra.frmultiple-starsexoplanetsradial-velocityspectroscopyvisible-astronomyThe low masses of M dwarfs create attractive opportunities for exoplanet radial-velocity (RV) detections. These stars, however, exhibit strong stellar activity that may attenuate or mimic planetary signals. We present a velocimetric analysis on one such M dwarf, GJ 3998 (d=18.2pc), with two published short-period super-Earths: GJ 3998 b and GJ 3998 c. We use additional data from the HARPS-N spectrograph to confirm these two planets and to look for more. We carry out joint modelling of: (i) RV planetary signals, (ii) stellar rotation in RV and activity indicators through Gaussian processes, (iii) long-term trends in RV and activity indicators. We constrain the rotational period of GJ 3998 to Prot=30.2+/-0.3d and discover long-term sinusoidal imprints in RV and FWHM of period Pcyc=316^+14^-_8_d. We confirm GJ 3998 b and GJ 3998 c, and detect a third planet: GJ 3998 d, whose signal had been previously attributed to stellar activity. GJ 3998 d has an orbital period of 41.78+/-0.05d, a minimum mass of 6.07^+1.00^_-0.96_M_{Earth}_ and a mean insolation flux of 1.2^+0.3^_-0.2_{PHI}_{Earth}_. This makes it one of the few known planets receiving Earth-like insolation flux.2025A&A...695A..62Shttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/695/A62CatalogResearchIsServedByTAP VizieR generic servicerelated-toJ/A+A/593/A117 : GJ 3998 RVs, S and Halpha indexes (Affer+, 2016)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/695/A62https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/695/A62http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/695/A62https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/695/A62https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/695/A62http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/695/A62GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapOpticaldefaultJ/A+A/695/A62/harpsnHARPS-N velocimetry of GJ 3998recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintBJDReduced Julian date (BJD-2400000)dtime.epochdoubleRVlblLine-by-line radial velocitym/sphys.veloc;pos.heliocentricdoublee_RVlblLine-by-line radial velocity errorm/sstat.errordoubleSMWMount Wilson S-indexphot.flux;arith.ratiodoubleRVccfCross-correlation function radial velocitym/sphys.veloc;pos.heliocentricdoublee_RVccfCross-correlation function radial velocity errorm/sstat.errordoubleFWHMccfFull width at half maximumm/sspect.line.widthdoublee_FWHMccfFull width at half maximum errorm/sstat.errordoublee_SMWMount Wilson S-index errorstat.errordoubleHalphaH-alpha indicatorspect.index;em.line.Halphadoublee_HalphaH-alpha indicator errorstat.error;spect.linedoubleNaINa I indicatorspect.indexdoublee_NaINa I indicator errorstat.errordouble