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Kepler-68: Three Planets, One with a Density between that of Earth and Ice Giants

Gilliland, Ronald L. and Rogers, Leslie and Howard, Andrew W. (2013) Kepler-68: Three Planets, One with a Density between that of Earth and Ice Giants. Astrophysical Journal, 766 (1). Art. No. 40. ISSN 0004-637X.

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NASA’s Kepler Mission has revealed two transiting planets orbiting Kepler-68. Follow-up Doppler measurements have established the mass of the innermost planet and revealed a third Jovian-mass planet orbiting beyond the two transiting planets. Kepler-68b, in a 5.4 day orbit, has M_P = 8.3^(+2.2)_(−2.4) M_⊕, R_P = 2.31^(+0.06)_(−0.09) R_⊕, and ρ_P = 3.32^(+0.86)_(−0.98) g cm^(−3), giving Kepler-68b a density intermediate between that of the ice giants and Earth. Kepler-68c is Earth-sized, with a radius R_P = 0.953^(+0.037)_(−0.042) R_⊕ and transits on a 9.6 day orbit; validation of Kepler-68c posed unique challenges. Kepler-68d has an orbital period of 580 ± 15 days and a minimum mass of M_P sin_i = 0.947 ± 0.035M_J . Power spectra of the Kepler photometry at one minute cadence exhibit a rich and strong set of asteroseismic pulsation modes enabling detailed analysis of the stellar interior. Spectroscopy of the star coupled with asteroseismic modeling of the multiple pulsation modes yield precise measurements of stellar properties, notably T_(eff) = 5793±74 K,M_★ = 1.079±0.051M_☉, R_★ = 1.243±0.019 R_☉, and ρ_★ = 0.7903±0.0054 g cm^(−3), all measured with fractional uncertainties of only a few percent. Models of Kepler-68b suggest that it is likely composed of rock and water, or has a H and He envelope to yield its density ∼3 g cm^(−3).

Item Type:Article
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Gilliland, Ronald L.0000-0002-1554-5578
Rogers, Leslie0000-0003-0638-3455
Howard, Andrew W.0000-0001-8638-0320
Additional Information:© 2013 American Astronomical Society. Received 2012 December 16; accepted 2013 February 8; published 2013 March 5. Funding for this tenth Discovery mission is provided by NASA’s Science Mission Directorate. The many people contributing to the development of this mission are gratefully acknowledged. We thank Elizabeth Adams, Eric Agol, Natalie Batalha, William Borucki, Stephen Bryson, William Cochran, Andrea Dupree, Debra Fischer, and David Monet for discussion and contributions. The anonymous referee made comments serving to improve the paper. Some of the data used here were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and NASA. The W. M. Keck Foundation provided generous financial support to the Keck Observatory. This work is also based in part on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA. Partial support for this work was provided by NASA through an award issued by JPL/Caltech. Support for L.A.R. was provided through Hubble Fellowship grant No. HF-51313.01-A awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA under contract NAS 5-26555. G.T. acknowledges partial support for this work from NASA grant NNX12AC75G (Kepler Participating Scientist Program). Funding for the Stellar Astrophysics Centre is provided by The Danish National Research Foundation. The research is supported by the ASTERISK project (ASTERoseismic Investigations with SONG and Kepler) funded by the European Research Council (grant agreement No. 267864). Asteroseismic analysis was supported in part by White Dwarf Research Corporation through the Pale Blue Dot project ( S.B. acknowledges support from NSF grant AST-1105930. R.L.G. has been partially supported by NASA co-operative agreement NNX09AG09A. Facility: Kepler
Funding AgencyGrant Number
W. M. Keck FoundationUNSPECIFIED
NASA Hubble FellowshipHF-51313.01-A
NASANAS 5-26555
Danish National Research FoundationUNSPECIFIED
European Research Council (ERC)267864 ASTERISK
White Dwarf Research Corporation Pale Blue Dot ProjectUNSPECIFIED
Subject Keywords:planetary systems; stars: fundamental parameters; stars: individual (Kepler-68, KIC 11295426, 2MASS J19240775+4902249)
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Record Number:CaltechAUTHORS:20130412-091623982
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Official Citation:Kepler-68: Three Planets, One with a Density between that of Earth and Ice Giants Ronald L. Gilliland et al. 2013 ApJ 766 40
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:37899
Deposited By: Ruth Sustaita
Deposited On:12 Apr 2013 16:47
Last Modified:03 Oct 2019 04:52

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