Kepler-18B, C, and D: A System of Three Planets Confirmed by Transit Timing Variations, Light Curve Validation, Warm-Spitzer Photometry, and Radial Velocity Measurements

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Cochran, William D.
Fabrycky, Daniel C.
Torres, Guillermo
Fressin, Francois
Desert, Jean-Michel
Ragozzine, Darin
Sasselov, Dimitar
Fortney, Jonathan J.
Rowe, Jason F.
Brugamyer, Erik J.

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We report the detection of three transiting planets around a Sun-like star, which we designate Kepler-18. The transit signals were detected in photometric data from the Kepler satellite, and were confirmed to arise from planets using a combination of large transit-timing variations (TTVs), radial velocity variations, Warm-Spitzer observations, and statistical analysis of false-positive probabilities. The Kepler-18 star has a mass of 0.97M(circle dot), a radius of 1.1R(circle dot), an effective temperature of 5345 K, and an iron abundance of [Fe/H] = +0.19. The planets have orbital periods of approximately 3.5, 7.6, and 14.9 days. The innermost planet "b" is a "super-Earth" with a mass of 6.9 +/- 3.4M(circle plus), a radius of 2.00 +/- 0.10R(circle plus), and a mean density of 4.9 +/- 2.4 g cm(3). The two outer planets "c" and "d" are both low-density Neptune-mass planets. Kepler-18c has a mass of 17.3 +/- 1.9 M-circle plus, a radius of 5.49 +/- 0.26R(circle plus), and a mean density of 0.59 +/- 0.07 g cm(3), while Kepler-18d has a mass of 16.4 +/- 1.4 M-circle plus, a radius of 6.98 +/- 0.33 R-circle plus and a mean density of 0.27 +/- 0.03 g cm(.)(3) Kepler-18c and Kepler-18d have orbital periods near a 2:1 mean-motion resonance, leading to large and readily detected TTVs.


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Cochran, William D., Daniel C. Fabrycky, Guillermo Torres, François Fressin, Jean-Michel Désert, Darin Ragozzine, Dimitar Sasselov et al. "Kepler-18b, c, and d: a system of three planets confirmed by transit timing variations, light curve validation, warm-spitzer photometry, and radial velocity measurements." The Astrophysical Journal Supplement Series, Vol. 197, No. 1 (Nov., 2011): 7.