J/ApJ/805/175ivo://CDS.VizieR/J/ApJ/805/175doi:10.26093/cds/vizier.18050175CDSFulton B.J.Weiss L.M.Sinukoff E.Isaacson H.Howard A.W.Marcy G.W.,Henry G.W.Holden B.P.Kibrick R.I.2017-07-05T06:59:22Z2015-10-20T14:01:43ZCDS support team

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

cds-question@unistra.frradial-velocitymultiple-starssolar-system-planetsWe report the discovery of two super-Earth-mass planets orbiting the nearby K0.5 dwarf HD 7924, which was previously known to host one small planet. The new companions have masses of 7.9 and 6.4M_{Earth}_, and orbital periods of 15.3 and 24.5 days. We perform a joint analysis of high-precision radial velocity data from Keck/HIRES and the new Automated Planet Finder Telescope (APF) to robustly detect three total planets in the system. We refine the ephemeris of the previously known planet using 5yr of new Keck data and high-cadence observations over the last 1.3yr with the APF. With this new ephemeris, we show that a previous transit search for the inner-most planet would have covered 70% of the predicted ingress or egress times. Photometric data collected over the last eight years using the Automated Photometric Telescope shows no evidence for transits of any of the planets, which would be detectable if the planets transit and their compositions are hydrogen-dominated. We detect a long-period signal that we interpret as the stellar magnetic activity cycle since it is strongly correlated with the CaII H and K activity index. We also detect two additional short-period signals that we attribute to rotationally modulated starspots and a one-month alias. The high-cadence APF data help to distinguish between the true orbital periods and aliases caused by the window function of the Keck data. The planets orbiting HD 7924 are a local example of the compact, multi-planet systems that the Kepler Mission found in great abundance.2015ApJ...805..175Fhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/805/175CatalogResearchIsServedByTAP VizieR generic servicerelated-toJ/ApJ/784/45 : Kepler's multiple planet candidates. III. (Rowe+, 2014)J/ApJS/210/20 : Small Kepler planets radial velocities (Marcy+, 2014)J/ApJ/772/80 : Radial velocities of HAT-P-17 (Fulton+, 2013)J/A+A/556/A150 : SWEETCat I. Stellar parameters for host stars (Santos+, 2013)J/ApJ/768/155 : RVs and photometry of HD 38529 system (Henry+, 2013)J/ApJS/204/24 : Kepler planetary candidates. III. (Batalha+, 2013)J/ApJ/757/112 : Stellar diameters. II. K and M-stars (Boyajian+, 2012)J/A+A/546/A61 : Radial velocities for XHIP catalogue (de Bruijne+, 2012)J/ApJS/197/8 : Kepler's candidate mult. transiting planets (Lissauer+, 2011)J/AJ/142/176 : Exoplanet host stars II. Speckle interferometry (Mason+, 2011)J/AJ/142/84 : 10 new transit light curves of HAT-P-13b (Fulton+, 2011)J/ApJ/733/68 : Exoplanet masses derived from RVs (Brown+, 2011)J/PASP/123/412 : Exoplanet Orbit Database (Wright+, 2011)J/ApJ/725/875 : Chromospheric activity for CPS stars (Isaacson+, 2010)J/other/Sci/330.653 : Detected planets in the Eta-Earth Survey (Howard+, 2010)J/other/A+ARV/18.67 : Accurate masses and radii of normal stars (Torres+, 2010)J/A+A/507/487 : GJ 581 radial velocity curve (Mayor+, 2009)J/ApJS/168/297 : Stellar parameters of nearby cool stars (Takeda+, 2007)J/ApJS/159/141 : Spectroscopic properties of cool stars. I. (Valenti+, 2005)http://exoplanets.org/ : Exoplanet Orbit database home pagehttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/805/175https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/805/175http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/805/175https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/805/175https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/805/175http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/805/175GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapOpticaldefaultJ/ApJ/805/175/table2Radial velocities of HD 7924recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintBJDTDBJulian Date in Barycentric Dynamical Timedtime.epochdoubleRV[-12.2/14.3] Radial Velocitym/sphys.veloc;pos.heliocentricfloate_RV[0.7/3.1] Uncertainty in RVm/sstat.errorfloatInstInstrument (1)meta.id;instrcharSHK[0.1/0.3]? CaII H&K stellar activity indexspect.indexfloatnullable