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Validation and Initial Characterization of the Long-period Planet Kepler-1654 b

Beichman, C. A. and Giles, H. A. C. and Akeson, R. and Ciardi, D. and Christiansen, J. and Isaacson, H. and Marcy, G. M. and Sinukoff, E. and Greene, T. and Fortney, J. J. and Crossfield, I. and Hu, R. and Howard, A. W. and Petigura, E. A. and Knutson, H. A. (2018) Validation and Initial Characterization of the Long-period Planet Kepler-1654 b. Astronomical Journal, 155 (4). Art. No. 158. ISSN 1538-3881. doi:10.3847/1538-3881/aaaeb6.

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Fewer than 20 transiting Kepler planets have periods longer than one year. Our early search of the Kepler light curves revealed one such system, Kepler-1654b (originally KIC 8410697b), which shows exactly two transit events and whose second transit occurred only five days before the failure of the second of two reaction wheels brought the primary Kepler mission to an end. A number of authors have also examined light curves from the Kepler mission searching for long-period planets and identified this candidate. Starting in 2014 September, we began an observational program of imaging, reconnaissance spectroscopy, and precision radial velocity (RV) measurements that confirm with a high degree of confidence that Kepler-1654b is a bona fide transiting planet orbiting a mature G5V star (T_(eff) = 5580 K, [Fe/H] = −0.08) with a semimajor axis of 2.03 au, a period of 1047.84 days, and a radius of 0.82 ± 0.02 R_(Jup). RV measurements using Keck's HIRES spectrometer obtained over 2.5 years set a limit to the planet's mass of <0.5 (3σ) M_(Jup). The bulk density of the planet is similar to that of Saturn or possibly lower. We assess the suitability of temperate gas giants like Kepler-1654b for transit spectroscopy with the James Webb Space Telescope, as their relatively cold equilibrium temperatures (T_(pl) ~ 200 K) make them interesting from the standpoint of exoplanet atmospheric physics. Unfortunately, these low temperatures also make the atmospheric scale heights small and thus transmission spectroscopy challenging. Finally, the long time between transits can make scheduling JWST observations difficult—as is the case with Kepler-1654b.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Beichman, C. A.0000-0002-5627-5471
Akeson, R.0000-0001-9674-1564
Ciardi, D.0000-0002-5741-3047
Christiansen, J.0000-0002-8035-4778
Isaacson, H.0000-0002-0531-1073
Marcy, G. M.0000-0002-2909-0113
Sinukoff, E.0000-0002-5658-0601
Greene, T.0000-0002-8963-8056
Fortney, J. J.0000-0002-9843-4354
Crossfield, I.0000-0002-1835-1891
Howard, A. W.0000-0001-8638-0320
Petigura, E. A.0000-0003-0967-2893
Knutson, H. A.0000-0002-0822-3095
Additional Information:© 2018. The American Astronomical Society. Received 2017 December 27; revised 2018 January 29; accepted 2018 February 8; published 2018 March 20. Some of the research described in this publication was carried out in part at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. This research has made use of the NASA/IPAC Infrared Science Archive (IRSA), the Keck Observatory Archive (KOA), and the NASA Exoplanet Archive, which are operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. We used the implementation of EXOFAST available at the NASA Exoplanet Science Institute. We are grateful to an anonymous referee for a careful reading of the manuscript, which led to a number of improvements. Some data presented herein were obtained at the W. M. Keck Observatory from telescope time allocated to the National Aeronautics and Space Administration through the agency's scientific partnership with the California Institute of Technology and the University of California. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. Finally, H.G. acknowledges support of a summer internship made possible by Caltech and JPL.
Group:Infrared Processing and Analysis Center (IPAC), Astronomy Department
Funding AgencyGrant Number
W. M. Keck FoundationUNSPECIFIED
Subject Keywords:planetary systems; planets and satellites: detection
Issue or Number:4
Record Number:CaltechAUTHORS:20180328-133305203
Persistent URL:
Official Citation:C. A. Beichman et al 2018 AJ 155 158
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:85472
Deposited By: George Porter
Deposited On:28 Mar 2018 21:11
Last Modified:15 Nov 2021 20:29

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