J/AJ/168/161ivo://CDS.VizieR/J/AJ/168/161doi:10.26093/cds/vizier/be-58-51CDSThygesen E.Rodriguez J.E.de Beurs Z.L.Vanderburg A.,Livingston J.H.Irwin J.Venner A.Cretignier M.Collins K.A.,Bieryla A.Charbonneau D.Crossfield I.J.M.Dumusque X.Kielkopf J.,Latham D.W.Werner M.2026-07-02T11:44:53Z2025-06-02T09:05:56ZCDS support team

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

cds-question@unistra.frexoplanetsinfrared-photometryvisible-astronomybroad-band-photometryradial-velocityspectroscopyK2-2 b/HIP 116454 b, the first exoplanet discovery by K2 during its Two-Wheeled Concept Engineering Test, is a sub-Neptune (2.5+/-0.1R_{Earth}_, 9.7+/-1.2M_{Earth}_) orbiting a relatively bright (KS=8.03) K-dwarf star on a 9.1d period. Unfortunately, due to a spurious follow-up transit detection and ephemeris degradation, the transit ephemeris for this planet was lost. In this work, we recover and refine the transit ephemeris for K2-2 b, showing a ~40{sigma} discrepancy from the discovery results. To accurately measure the transit ephemeris and update the parameters of the system, we jointly fit space-based photometric observations from NASA's K2, Transiting Exoplanet Survey Satellite, and Spitzer missions with new photometric observations from the ground, as well as radial velocities from HARPS-N that are corrected for stellar activity using a new modeling technique. Ephemerides becoming lost or significantly degraded, as is the case for most transiting planets, highlights the importance of systematically updating transit ephemerides with upcoming large efforts expected to characterize hundreds of exoplanet atmospheres. K2-2 b sits at the high-mass peak of the known radius valley for sub-Neptunes, and is now well-suited for transmission spectroscopy with current and future facilities. Our updated transit ephemeris will ensure no more than a 13min uncertainty through 2030.2024AJ....168..161Thttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/AJ/168/161CatalogResearchIsServedByTAP VizieR generic servicerelated-toII/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)I/311 : Hipparcos, the New Reduction (van Leeuwen, 2007)II/294 : The SDSS Photometric Cat. R7 (Adelman-McCarthy+, 2009)IV/34 : K2 Ecliptic Plane Input Catalog (EPIC) (Huber+, 2017)IV/39 : TESS Input Catalog version 8.2 (TIC v8.2) (Paegert+, 2021)I/355 : Gaia DR3 Part 1. Main source (Gaia Collaboration, 2022)J/ApJ/683/1076 : Transits of exoplanet XO-3b (Winn+, 2008)J/ApJ/736/12 : Transit light curves of GJ1214 (Berta+, 2011)J/A+A/529/A75 : Limb-darkening coefficients (Claret+, 2011)J/other/Nat/486.375 : Stellar parameters of KOI stars (Buchhave+, 2012)J/ApJ/791/35 : Detect: 715 Kepler planet candid. host stars (Law+, 2014)J/ApJS/226/7 : Planet candid. discov.: K2's 1st yr (Crossfield+, 2016)J/ApJS/222/14 : Planetary candid.: 1st yr K2 mission (Vanderburg+, 2016)J/A+A/600/A30 : Limb-darkening for TESS satellite (Claret, 2017)J/AJ/154/109 : CKS. III. Planet radii (Fulton+, 2017)J/AJ/156/277 : 60 valid planets: K2 campaigns 5-8 (Livingston+, 2018)J/AJ/156/102 : TESS Input Cat. & Candidate Target List (Stassun+, 2018)J/A+A/610/A20 : HITEP. II. Transiting exoplanets imaging (Evans+, 2018)J/AJ/157/169 : Identify exoplanets: deep learning in K2 (Dattilo+, 2019)J/AJ/157/174 : Transiting planets in Kepler-47 system (Orosz+, 2019)J/ApJS/244/11 : Planet candidates & EBs: K2 campaigns 0-8 (Kruse+, 2019)J/AJ/160/209 : K2 & TESS Syn. I. Param & LC, 4 stars (Ikwut-Ukwa+, 2020)J/ApJS/254/42 : Hipparcos-Gaia (EDR3) Cat. of Accelerat. (Brandt, 2021)J/A+A/648/A103 : Thorium line list (Dumusque+, 2021)J/MNRAS/508/3877 : Catalogue of white dwarfs in Gaia EDR3 (Gentile+, 2021)J/AJ/162/259 : Scal K2. IV. Camp 1-8 & 10-18 planets samp (Zink+, 2021)J/ApJS/258/40 : ExoClock proj II. Exoplanet ephemerids (Kokori+, 2022)J/A+A/677/A33 : 38 Kepler and K2 systems RVs (Bonomo+, 2023)J/A+A/678/A2 : YARARA V2. 4 high-PM stars RVs (Cretignier+, 2023)J/ApJS/265/4 : ExoClock proj III. 450 exoplanet ephemeri (Kokori+, 2023)J/A+A/678/A90 : HD99492,HD147379,HD190007 HARPS-N data (Stalport+, 2023)J/MNRAS/527/2940 : Sol activity components intensity prof (Cretignier+ 2024)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/AJ/168/161https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/AJ/168/161http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/AJ/168/161https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/AJ/168/161https://vizier.iucaa.in/viz-bin/votable?-source=J/AJ/168/161http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/AJ/168/161GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapOpticalInfrareddefaultJ/AJ/168/161/k2K2 light curve of K2-2 b (Data behind Figure 1)recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintBJDBarycentric Julian Date of Observation at TDBdtime.epochdoubleFlux[0.998/1.01] Normalized Fluxphot.flux;arith.ratiodoublee_FluxUncertainty in Fluxstat.error;phot.fluxdoubleJ/AJ/168/161/mearthMEarth (custom 715nm) light curve of K2-2 b (Data behind Figure 1)recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintTelMEarth Telescopeinstr.telcharBJDBarycentric Julian Date of Observation at TDBdtime.epochdoubleFlux[0.77/1.06] Normalized Fluxphot.flux;arith.ratiodoublee_Flux[1e-3/70e-3] Uncertainty in Fluxstat.error;phot.fluxdoubleAirmass[1.16/2.93] Airmass of observationobs.airMassdoubleJ/AJ/168/161/spitzerSpitzer 4.5um light curve of K2-2 b (Data behind Figure 1)recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintBJDBarycentric Julian Date of Observation at TDBdtime.epochdoubleFlux[0.997/1.01] Normalized Fluxphot.flux;arith.ratiodoublee_Flux[6e-4/6.5e-4] Uncertainty in Fluxstat.error;phot.fluxdoubleJ/AJ/168/161/tessTESS T band light curve of K2-2 b (Data behind Figure 1)recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintSectTESS Sectormeta.id;obscharBJDBarycentric Julian Date of Observation at TDBdtime.epochdoubleindexedFlux[0.996/1.01] Normalized Fluxphot.flux;arith.ratiodoublee_Flux[7.6e-4/7.7e-4] Uncertainty in Fluxstat.error;phot.fluxdoubleJ/AJ/168/161/ulmtULMT r' band light curve of K2-2 b (Data behind Figure 1)recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintBJDBarycentric Julian Date of Observation at TDBdtime.epochdoubleFlux[0.948/1.02] Normalized Fluxphot.flux;arith.ratiodoublee_Flux[8e-4/2.5e-2] Uncertainty in Fluxstat.error;phot.fluxdoubleAirmass[1.16/2.92] Airmass of observationobs.airMassdoubleJ/AJ/168/161/fig2HARPS-N RVs and cross-correlation functionsccf5[-2.5e-3/1.8e-3] Cross-Correlation function, location 5stat.correlationdoublerecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintBJDBarycentric Julian Date of Observation at TDBdtime.epochdoubleRVel[-9.8/11.4] HARPS-N Radial Velocitym/sspect.dopplerVelocdoublee_RVel[0.8/3.2] Uncertainty in RVelm/sstat.error;spect.dopplerVelocdoubleccf1[-1.6e-3/2.7e-3] Cross-Correlation function, location 1stat.correlationdoubleccf2[-2.5e-3/4.2e-3] Cross-Correlation function, location 2stat.correlationdoubleccf3[-3.6e-3/4.6e-3] Cross-Correlation function, location 3stat.correlationdoubleccf4[-3.5e-3/3.9e-3] Cross-Correlation function, location 4stat.correlationdouble