The Kepler-454 System: A Small, Not-rocky Inner Planet, a Jovian World, and a Distant Companion

Creators: Gettel, Sara; Dressing, Courtney D.; Howard, Andrew W.

Abstract

Kepler-454 (KOI-273) is a relatively bright (V = 11.69 mag), Sun-like star that hosts a transiting planet candidate in a 10.6 day orbit. From spectroscopy, we estimate the stellar temperature to be 5687 ± 50 K, its metallicity to be [m/H] = 0.32 ± 0.08, and the projected rotational velocity to be v sin i < 2.4 km s^(−1). We combine these values with a study of the asteroseismic frequencies from short cadence Kepler data to estimate the stellar mass to be 1.028_(-0.03)^(+0.04)M_☉ , the radius to be 1.066 ± 0.012 R_⊙, and the age to be 5.25_(-1.39)^(+1.41)Gyr. We estimate the radius of the 10.6 day planet as 2.37 ± 0.13 R_⊕. Using 63 radial velocity observations obtained with the HARPS-N spectrograph on the Telescopio Nazionale Galileo and 36 observations made with the HIRES spectrograph at the Keck Observatory, we measure the mass of this planet to be 6.8 ± 1.4 M_⊕. We also detect two additional non-transiting companions, a planet with a minimum mass of 4.46 ± 0.12 MJ in a nearly circular 524 day orbit and a massive companion with a period >10 years and mass >12.1 MJ. The 12 exoplanets with radii <2.7 R_⊕ and precise mass measurements appear to fall into two populations, with those <1.6 R_⊕ following an Earth-like composition curve and larger planets requiring a significant fraction of volatiles. With a density of 2.76 ± 0.73 g cm^(−3), Kepler-454b lies near the mass transition between these two populations and requires the presence of volatiles and/or H/He gas.

Additional Information

© 2016 American Astronomical Society. Received 2015 May 29; accepted 2015 November 23; published 2016 January 14. The authors would like to thank the TNG observers who contributed to the measurements reported here, including Walter Boschin, Massimo Cecconi, Vania Lorenzi and Marco Pedani. We also thank Lauren Weiss for gathering some of the HIRES data presented here. The authors wish to thank the entire Kepler team, without whom these results would not be possible. Funding for this Discovery mission is provided by NASA's Science Mission Directorate. The HARPS-N project was funded by the Prodex Program of the Swiss Space Office (SSO), the Harvard University Origin of Life Initiative (HUOLI), the Scottish Universities Physics Alliance (SUPA), the University of Geneva, the Smithsonian Astrophysical Observatory (SAO), and the Italian National Astrophysical Institute (INAF), University of St. Andrews, Queen's University Belfast and University of Edinburgh. The research leading to these results has received funding from the European Union Seventh Framework Programme (FP7/2007-2013) under grant Agreement No. 313014 (ETAEARTH). This publication was made possible by a grant from the John Templeton Foundation. The opinions expressed in this publication are those of the authors and do not necessarily reflect the views of the John Templeton Foundation. This material is based upon work supported by the National Aeronautics and Space Administration under grant No. NNX15AC90G issued through the Exoplanets Research Program. C.D. is supported by a National Science Foundation Graduate Research Fellowship. Work by C.D. was performed in part under contract with the California Institute of Technology (Caltech)/Jet Propulsion Laboratory (JPL) funded by NASA through the Sagan Fellowship Program executed by the NASA Exoplanet Science Institute. X.D. would like to thank the Swiss National Science Foundation (SNSF) for its support through an Early Postdoc Mobility fellowship. A.V. is supported by the National Science Foundation Graduate Research Fellowship, grant No. DGE 1144152. P. F. acknowledges support by Fundação para a Ciência e a Tecnologia (FCT) through Investigador FCT contracts of reference IF/01037/2013 and POPH/FSE (EC) by FEDER funding through the program "Programa Operacional de Factores de Competitividade—COMPETE". P.F. further acknowledges support from Fundação para a Ciência e a Tecnologia (FCT) in the form of an exploratory project of reference IF/01037/2013CP1191/CT0001. W.J.C., T.L.C. and G.R.D. acknowledge the support of the UK Science and Technology Facilities Council (STFC). S.B. acknowledges partial support from NSF grant AST-1105930 and NASA grant NNX13AE70G. T.S.M. was supported by NASA grant NNX13AE91G. Computational time on Stampede at the Texas Advanced Computing Center was provided through XSEDE allocation TG-AST090107. Funding for the Stellar Astrophysics Centre is provided by The Danish National Research Foundation (grant agreement No.: DNRF106). The research is supported by the ASTERISK project (ASTERoseismic Investigations with SONG and Kepler) funded by the European Research Council (grant agreement No.: 267864); and by the European Community's Seventh Framework Programme (FP7/2007-2013) under grant agreement No. 312844 (SPACEINN). Partial support was received from the Kepler mission under NASA Cooperation Agreement NNX13AB58A to the Smithsonian Astrophysical Observatory (PI:DWL). Some of the data presented herein 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 the National Aeronautics and Space Administration. The Keck Observatory was made possible by the generous financial support of the W. M. Keck Foundation. The spectra and their products are made available at the NExSci Exoplanet Archive and its CFOP website: http://exoplanetarchive.ipac.caltech.edu. We thank the many observers who contributed to the HIRES measurements reported here, including Benjamin J. Fulton, Evan Sinukoff, and Lea Hirsch. We gratefully acknowledge the efforts and dedication of the Keck Observatory staff, especially Greg Doppmann, Scott Dahm, Hien Tran, and Grant Hill for support of HIRES and Greg Wirth and Bob Goodrich for support of remote observing. This research has made use of the NASA Exoplanet Archive, which is operated by the California Institute of Technology, under contract with the National Aeronautics and Space Administration under the Exoplanet Exploration Program. Finally, the authors wish to extend special thanks to those of Hawaiian ancestry on whose sacred mountain of Mauna Kea we are privileged to be guests. Without their generous hospitality, the Keck observations presented herein would not have been possible.

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