J/AJ/168/231ivo://CDS.VizieR/J/AJ/168/231doi:10.26093/cds/vizier/be-58-77CDSSing D.K.Evans-Soma T.M.Rustamkulov Z.Lothringer J.D.Mayne N.J.,Schlaufman K.C.2026-07-02T11:45:00Z2025-07-08T08:44:27ZCDS support team

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

cds-question@unistra.frradial-velocityexoplanetsspectroscopyinfrared-astronomyWe have conducted a planetary radial velocity measurement of the ultrahot Jupiter WASP-121b using JWST NIRSpec phase curve data. Our analysis reveals the Doppler shift of the planetary spectral lines across the full orbit, which shifts considerably across the detector (~10 pixels). Using cross-correlation techniques, we have determined an overall planetary velocity amplitude of K_p_=215.7+/-1.1km/s, which is in good agreement with the expected value. We have also calculated the dynamical mass for both components of the system by treating it as an eclipsing double-line spectroscopic binary, with WASP-121A having a mass of M_s_=1.330+/-0.019M_{sun}_, while WASP-121b has a mass of M_p_=1.170+/-0.043M_J_. These dynamical measurements are ~3x more precise than previous estimates and do not rely on any stellar modeling assumptions that have a ~5% systematic floor mass uncertainty. Additionally, we used stellar evolution modeling constrained with a stellar density and parallax measurement to determine a precise age for the system, found to be 1.11+/-0.14Gyr. Finally, we observed potential velocity differences between the two NIRSpec detectors, with NRS1 lower by 5.5+/-2.2km/s. We suggest that differences can arise from day/night asymmetries in the thermal emission, which can lead to a sensitivity bias favoring the illuminated side of the planet, with planetary rotation and winds both acting to lower a measured K_p_. The planet's rotation can account for 1km/s of the observed velocity difference, with 4.5+/-2.2km/s potentially attributable to vertical differences in wind speeds.2024AJ....168..231Shttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/AJ/168/231CatalogResearchIsServedByTAP VizieR generic servicerelated-toI/352 : Distances to 1.47 billion stars in Gaia EDR3 (Bailer-Jones+, 2021)II/365 : The CatWISE2020 cat. (updated version 28-Jan-2021) (Marocco+, 2021)I/357 : Gaia DR3 Part 3. Non-single stars (Gaia Collaboration, 2022)VII/233 : 2MASS All-Sky Extended Source Catalog (XSC) (IPAC/UMass, 2003-2006)J/other/A+ARV/18.67 : Accurate masses and radii of normal stars (Torres+, 2010)J/AJ/153/138 : Radial velocity curve of 51 Peg (Birkby+, 2017)J/A+A/623/A57 : WASP-121 b Swift UVOT near-UV transit obs. (Salz+, 2019)J/A+A/625/A80 : WASP-121b secondary eclipse: 2MASS K band (Kovacs+, 2019)J/A+A/631/A77 : Low-mass stellar models and isochrones (Amard+, 2019)J/AJ/157/55 : RVs and light curves for HATS-60-HATS-69 (Hartman+, 2019)J/A+A/635/A205 : Ultra-hot Jupiter WASP-121b transits (Bourrier+, 2020)J/A+A/637/A36 : WASP-121b optical phase curve (Bourrier+, 2020)J/ApJ/888/L5 : Transits, occultation times and RVs of WASP-12b (Yee+, 2020)J/A+A/661/A147 : Gal. interstellar dust Gaia-2MASS 3D maps (Lallement+, 2022)J/A+A/664/A174 : Gal. interstellar dust Gaia-2MASS 3D maps (Vergely+, 2022)J/MNRAS/518/662 : Benchmarking MESA isochrones with Hyades (Brandner+, 2023)J/ApJ/946/L6 : JWST NIRSp. & MIRI sp. of BD* SIPS J1256-1257B (Miles+, 2023)J/ApJS/265/1 : TESS Grand Unified Hot Jupiter Surveys. II. (Yee+, 2023)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/AJ/168/231https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/AJ/168/231http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/AJ/168/231https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/AJ/168/231https://vizier.iucaa.in/viz-bin/votable?-source=J/AJ/168/231http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/AJ/168/231GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapInfrareddefaultJ/AJ/168/231/fig6Planetary RV signal derived using NIRSpec/NRS2recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintBJDBarycentric Julian Date; BJD-24500000.5 (TDB)dtime.epochdoublePhaseOrbital phasetime.phasefloatRVel[-235/226] Radial velocitykm/sspect.dopplerVelocfloate_RVel[6.9/58] 1{sigma} uncertainty in RVelkm/sstat.error;spect.dopplerVelocfloatJ/AJ/168/231/fig7Planetary RV signal derived using NIRSpec/NRS1recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintBJDBarycentric Julian Date; BJD-24500000.5 (TDB)dtime.epochdoublePhaseOrbital phasetime.phasefloatRVel[-235/226] Radial velocitykm/sspect.dopplerVelocfloate_RVel[6.9/58] 1{sigma} uncertainty in RVelkm/sstat.error;spect.dopplerVelocfloat