J/ApJ/733/127ivo://CDS.VizieR/J/ApJ/733/127doi:10.26093/cds/vizier.17330127CDSSanchis-Ojeda R.Winn J.N.Holman M.J.Carter J.A.Osip D.J.,Fuentes C.I.2017-06-26T11:49:52Z2012-12-12T13:05:31ZCDS support team

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

cds-question@unistra.frphotometrysolar-system-planetsmultiple-starsWe present photometry of four transits of the exoplanet WASP-4b, each with a precision of approximately 500ppm and a time sampling of 40-60s. We have used the data to refine the estimates of the system parameters and ephemerides. During two of the transits we observed a short-lived, low-amplitude anomaly that we interpret as the occultation of a starspot by the planet. We also found evidence for a pair of similar anomalies in previously published photometry. The recurrence of these anomalies suggests that the stellar rotation axis is nearly aligned with the orbital axis, or else the starspot would not have remained on the transit chord. By analyzing the timings of the anomalies we find the sky-projected stellar obliquity to be {lambda}=-1^+14^_-12_degrees. This result is consistent with (and more constraining than) a recent observation of the Rossiter-McLaughlin effect. It suggests that the planet migration mechanism preserved the initially low obliquity, or else that tidal evolution has realigned the system. Future applications of this method using data from the CoRoT and Kepler missions will allow spin-orbit alignment to be probed for many other exoplanets.2011ApJ...733..127Shttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/733/127CatalogResearchIsServedByTAP VizieR generic servicerelated-toJ/MNRAS/422/2024 : X-ray-age relation & exoplanet evaporation (Jackson+, 2012)J/A+A/539/A159 : WASP-4b transit griz light curves (Nikolov+, 2012)J/A+A/530/A5 : WASP-4b Ks detection of thermal emission (Caceres+, 2011)J/MNRAS/414/1278 : Eccentricities of transiting planets (Pont+, 2011)J/MNRAS/411/L46 : Exoplanet magnetic fields (Vidotto+, 2011)J/A+A/524/A25 : Radial Velocities on 6 exoplanet host stars (Triaud+, 2010)J/ApJ/716/1336 : Stability analysis of single-planet (Kopparapu+, 2010)J/MNRAS/399/287 : Transiting planetary system WASP-4 (Southworth+, 2009)J/AJ/137/3826 : Two transits of the giant planet WASP-4b (Winn+, 2009)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/733/127https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/733/127http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/733/127https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/733/127https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/733/127http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/733/127GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapOpticaldefaultJ/ApJ/733/127/table2Photometry of WASP-4recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintBJDBarycentric Julian Date (1)dtime.epochdoubleRFluxRelative fluxphot.flux;arith.ratiodoublee_RFluxUncertainty in RFluxstat.errordoubleAirAirmassobs.airMassfloat