J/AJ/152/204ivo://CDS.VizieR/J/AJ/152/204doi:10.26093/cds/vizier.51520204CDSLopez-morales M.Haywood R.D.Coughlin J.L.Zeng L.Buchhave L.A.,Giles H.A.C.Affer L.Bonomo A.S.Charbonneau D.Collier Cameron A.,Consentino R.Dressing C.D.Dumusque X.Figueira P.Fiorenzano A.F.M.,Harutyunyan A.Johnson J.A.Latham D.W.Lopez E.D.Lovis C.,Malavolta L.Mayor M.Micela G.Molinari E.Mortier A.Motalebi F.,Nascimbeni V.Pepe F.Phillips D.F.Piotto G.Pollacco D.Queloz D.,Rice K.Sasselov D.Segransan D.Sozzetti A.Udry S.Vanderburg A.,Watson C.2017-06-13T11:08:45Z2017-01-31T12:54:56ZCDS support team

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

cds-question@unistra.frsolar-system-planetsmultiple-starsradial-velocityHD 179070, aka Kepler-21, is a V=8.25 F6IV star and the brightest exoplanet host discovered by Kepler. An early detailed analysis by Howell et al. of the first 13 months (Q0-Q5) of Kepler light curves revealed transits of a planetary companion, Kepler-21b, with a radius of about 1.60+/-0.04R_{Earth}_ and an orbital period of about 2.7857days. However, they could not determine the mass of the planet from the initial radial velocity (RV) observations with Keck-HIRES, and were only able to impose a 2{sigma} upper limit of 10M_{Earth}_. Here, we present results from the analysis of 82 new RV observations of this system obtained with HARPS-N, together with the existing 14 HIRES data points. We detect the Doppler signal of Kepler-21b with a RV semiamplitude K=2.00+/-0.65ms^-1^, which corresponds to a planetary mass of 5.1+/-1.7M_{Earth}_. We also measure an improved radius for the planet of 1.639 +0.019/-0.015R_{Earth}_, in agreement with the radius reported by Howell et al. We conclude that Kepler-21b, with a density of 6.4+/-2.1gcm^-3^, belongs to the population of small, <~6M_{Earth}_ planets with iron and magnesium silicate interiors, which have lost the majority of their envelope volatiles via stellar winds or gravitational escape. The RV analysis presented in this paper serves as an example of the type of analysis that will be necessary to confirm the masses of TESS small planet candidates.2016AJ....152..204Lhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/AJ/152/204CatalogResearchIsServedByTAP VizieR generic servicerelated-toV/133 : Kepler Input Catalog (Kepler Mission Team, 2009)J/AJ/152/160 : HARPS-N radial velocities of KOI-70 (Buchhave+, 2016)J/MNRAS/452/2127 : Parameters of Kepler stars (Silva Aguirre+, 2015)J/ApJ/800/135 : HARPS-N radial velocities of KOI-69 (Dressing+, 2015)J/A+A/584/A72 : A transiting rocky planet at 6.5pc from Sun (Motalebi+ 2015)J/A+A/575/L15 : TrES-4b RV and Ic curves (Sozzetti+, 2015)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/AJ/152/204https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/AJ/152/204http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/AJ/152/204https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/AJ/152/204https://vizier.iucaa.in/viz-bin/votable?-source=J/AJ/152/204http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/AJ/152/204GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapOpticaldefaultJ/AJ/152/204/table4HARPS-N radial velocity dataBJDBarycentric Julian Date (UTC; BJD-2400000)dtime.epochdoublerecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintRV[-19182.1/-19160.1] Radial velocitym/sphys.veloc;pos.heliocentricdoublee_RV[0.88/6] The 1{sigma} uncertainty in RVm/sstat.errorfloatBS[36/58.1] Bisector spanm/sphys.velocfloatlogR'HK[-5.1/-4.9] Measured log R'_HK_ activity indexphot.flux;arith.ratiofloate_logR'HK[0.0019/0.033] 1{sigma} uncertainty in logR'HKstat.errorfloatExp[600/1800] Exposure time (t_exp_)stime.duration;obs.exposureint