J/AJ/156/89ivo://CDS.VizieR/J/AJ/156/89doi:10.26093/cds/vizier.51560089CDSPetigura E.A.Benneke B.Batygin K.Fulton B.J.Werner M.Krick J.E.,Gorjian V.Sinukoff E.Deck K.M.Mills S.M.Deming D.2019-03-07T14:03:12Z2019-02-28T12:40:20ZCDS support team

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

cds-question@unistra.frmultiple-starsexoplanetsradial-velocitystellar-evolutionary-modelsWhile planets between the size of Uranus and Saturn are absent within the solar system, the star K2-24 hosts two such planets, K2-24b and c, with radii equal to 5.4 R_{Earth}_ and 7.5 R_{Earth}_, respectively. The two planets have orbital periods of 20.9 days and 42.4 days, residing only 1% outside the nominal 2:1 mean-motion resonance. In this work, we present results from a coordinated observing campaign to measure planet masses and eccentricities that combines radial velocity measurements from Keck/HIRES and transit-timing measurements from K2 and Spitzer. K2-24b and c have low, but nonzero, eccentricities of e_1_~e_2_~0.08. The low observed eccentricities provide clues to the formation and dynamical evolution of K2-24b and K2-24c, suggesting that they could be the result of stochastic gravitational interactions with a turbulent protoplanetary disk, among other mechanisms. K2-24b and c are 19.0_-2.1_^+2.2^ M_{Earth}_ and 15.4_-1.8_^+1.9^ M_{Earth}_, respectively; K2-24c is 20% less massive than K2-24b, despite being 40% larger. Their large sizes and low masses imply large envelope fractions, which we estimate at 26_-3_^+3^ % and 52_-3_^+5^ %. In particular, K2-24c's large envelope presents an intriguing challenge to the standard model of core-nucleated accretion that predicts the onset of runaway accretion when f_env_~50%.2018AJ....156...89Phttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/AJ/156/89CatalogResearchIsServedByTAP VizieR generic servicerelated-toJ/ApJ/750/114 : Kepler TTVs. IV. 4 multiple-planet systems (Fabrycky+, 2012)J/ApJ/787/80 : 139 Kepler planets transit time variations (Hadden+, 2014)J/ApJS/210/20 : Small Kepler planets radial velocities (Marcy+, 2014)J/AJ/153/142 : Radial velocities of systems hosting sub-SaturnsJ/AJ/154/5 : Transit timing variations of 145 Kepler planets (Hadden+, 2017)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/AJ/156/89https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/AJ/156/89http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/AJ/156/89https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/AJ/156/89https://vizier.iucaa.in/viz-bin/votable?-source=J/AJ/156/89http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/AJ/156/89GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapdefaultJ/AJ/156/89/table2Radial velocitiesrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintBJDBarycentric Julian Date in Barycentric Dynamical Time (BJD-2454833; TDB)dtime.epochdoubleRV[-14.14/14.2] Barycentric radial velocitym/sphys.veloc;pos.barycenterfloate_RV[1.52/2.09] Uncertainty in RVm/sstat.errorfloatSHK[0.094/0.143] Mount Wilson S_HK_ activity index (1)spect.indexfloatJ/AJ/156/89/table4Predicted transit times for K2-24 planet b or crecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintPlanet[bc] K2-24 planet b or cmeta.code.multipchari[0/197] Individual transit indexmeta.numberintDateUTC datetime.epochnullableBJDPredicted transit time in Barycentric Dynamical Time (BJD-2454833; TDB)dtime.epochdoublee_BJDUncertainty in BJDdstat.errorfloat