Kepler-20: A Sun-Like Star With Three Sub-Neptune Exoplanets And Two Earth-Size Candidates

dc.contributor.utaustinauthorCochran, William D.en_US
dc.contributor.utaustinauthorEndl, Michaelen_US
dc.creatorGautier, Thomas N., IIIen_US
dc.creatorCharbonneau, Daviden_US
dc.creatorRowe, Jason F.en_US
dc.creatorMarcy, Geoffrey W.en_US
dc.creatorIsaacson, Howarden_US
dc.creatorTorres, Guillermoen_US
dc.creatorFressin, Francoisen_US
dc.creatorRogers, Leslie A.en_US
dc.creatorDesert, Jean-Michelen_US
dc.creatorBuchhave, Lars A.en_US
dc.creatorLatham, David W.en_US
dc.creatorQuinn, Samuel N.en_US
dc.creatorCiardi, David R.en_US
dc.creatorFabrycky, Daniel C.en_US
dc.creatorFord, Eric B.en_US
dc.creatorGilliland, Ronald L.en_US
dc.creatorWalkowicz, Lucianne M.en_US
dc.creatorBryson, Stephen T.en_US
dc.creatorCochran, William D.en_US
dc.creatorEndl, Michaelen_US
dc.creatorFischer, Debra A.en_US
dc.creatorHowell, Steve B.en_US
dc.creatorHorch, Elliott P.en_US
dc.creatorBarclay, Thomasen_US
dc.creatorBatalha, Natalieen_US
dc.creatorBorucki, William J.en_US
dc.creatorChristiansen, Jessie L.en_US
dc.creatorGeary, John C.en_US
dc.creatorHenze, Christopher E.en_US
dc.creatorHolman, Matthew J.en_US
dc.creatorIbrahim, Khadeejahen_US
dc.creatorJenkins, Jon M.en_US
dc.creatorKinemuchi, Karenen_US
dc.creatorKoch, David G.en_US
dc.creatorLissauer, Jack J.en_US
dc.creatorSanderfer, Dwight T.en_US
dc.creatorSasselov, Dimitar D.en_US
dc.creatorSeager, Saraen_US
dc.creatorSilverio, Kathrynen_US
dc.creatorSmith, Jeffrey C.en_US
dc.creatorStill, Martinen_US
dc.creatorStumpe, Martin C.en_US
dc.creatorTenenbaum, Peteren_US
dc.creatorVan Cleve, Jeffreyen_US
dc.description.abstractWe present the discovery of the Kepler-20 planetary system, which we initially identified through the detection of five distinct periodic transit signals in the Kepler light curve of the host star 2MASS J19104752+4220194. From high-resolution spectroscopy of the star, we find a stellar effective temperature T-eff = 5455 +/- 100 K, a metallicity of [Fe/H] = 0.01 +/- 0.04, and a surface gravity of log g = 4.4 +/- 0.1. We combine these estimates with an estimate of the stellar density derived from the transit light curves to deduce a stellar mass of M-* = 0.912 +/- 0.034M(circle dot) and a stellar radius of R-* = 0.944(-0.095)(+0.060) R-circle dot. For three of the transit signals, we demonstrate that our results strongly disfavor the possibility that these result from astrophysical false positives. We accomplish this by first identifying the subset of stellar blends that reproduce the precise shape of the light curve and then using the constraints on the presence of additional stars from high angular resolution imaging, photometric colors, and the absence of a secondary component in our spectroscopic observations. We conclude that the planetary scenario is more likely than that of an astrophysical false positive by a factor of 2x10(5) (Kepler-20b), 1x10(5) (Kepler-20c), and 1.1x10(3) (Kepler-20d), sufficient to validate these objects as planetary companions. For Kepler-20c and Kepler-20d, the blend scenario is independently disfavored by the achromaticity of the transit: from Spitzer data gathered at 4.5 mu m, we infer a ratio of the planetary to stellar radii of 0.075 +/- 0.015 (Kepler-20c) and 0.065 +/- 0.011 (Kepler-20d), consistent with each of the depths measured in the Kepler optical bandpass. We determine the orbital periods and physical radii of the three confirmed planets to be 3.70 days and 1.91(-0.21)(+0.12) R-circle plus for Kepler-20b, 10.85 days and 3.07(-0.31)(+0.20) R-circle plus for Kepler-20c, and 77.61 days and 2.75(-0.30)(+0.17) R-circle plus for Kepler-20d. From multi-epoch radial velocities, we determine the masses of Kepler-20b and Kepler-20c to be 8.7 +/- 2.2M(circle plus) and 16.1 +/- 3.5M(circle plus), respectively, and we place an upper limit on the mass of Kepler-20d of 20.1M(circle plus) (2 sigma).en_US
dc.description.departmentMcDonald Observatoryen_US
dc.description.sponsorshipNASA's Science Mission Directorateen_US
dc.description.sponsorshipNASA through JPL/Caltechen_US
dc.description.sponsorshipW. M. Keck Foundationen_US
dc.identifier.citationGautier III, Thomas N., David Charbonneau, Jason F. Rowe, Geoffrey W. Marcy, Howard Isaacson, Guillermo Torres, Francois Fressin et al. "Kepler-20: A Sun-like star with three sub-Neptune exoplanets and two Earth-size candidates." The Astrophysical Journal, Vol. 749, No. 1 (Apr., 2012): 15.en_US
dc.relation.ispartofserialAstrophysical Journalen_US
dc.rightsAdministrative deposit of works to Texas ScholarWorks: This works author(s) is or was a University faculty member, student or staff member; this article is already available through open access or the publisher allows a PDF version of the article to be freely posted online. The library makes the deposit as a matter of fair use (for scholarly, educational, and research purposes), and to preserve the work and further secure public access to the works of the University.en_US
dc.subjectplanetary systemsen_US
dc.subjectstars: individual (kepler-20, kic 6850504,en_US
dc.subject2mass j19104752+4220194)en_US
dc.subjecttransit timing variationsen_US
dc.subject1st 4 monthsen_US
dc.subjectextrasolar planeten_US
dc.subjectadaptive opticsen_US
dc.subjecthd 189733ben_US
dc.subjectinitial characteristicsen_US
dc.subjectastronomy & astrophysicsen_US
dc.titleKepler-20: A Sun-Like Star With Three Sub-Neptune Exoplanets And Two Earth-Size Candidatesen_US

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