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The Kepler-19 System: A Transiting 2.2 R_⊕ Planet and a Second Planet Detected via Transit Timing Variations

Ballard, Sarah and Ciardi, David R. (2011) The Kepler-19 System: A Transiting 2.2 R_⊕ Planet and a Second Planet Detected via Transit Timing Variations. Astrophysical Journal, 743 (2). Art. No. 200. ISSN 0004-637X.

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We present the discovery of the Kepler-19 planetary system, which we first identified from a 9.3 day periodic transit signal in the Kepler photometry. From high-resolution spectroscopy of the star, we find a stellar effective temperature T_(eff) = 5541 ± 60 K, a metallicity [Fe/H] = –0.13 ± 0.06, and a surface gravity log(g) = 4.59 ± 0.10. We combine the estimate of T_(eff) and [Fe/H] with an estimate of the stellar density derived from the photometric light curve to deduce a stellar mass of M_*= 0.936 ± 0.040 M_☉ and a stellar radius of R_* = 0.850 ± 0.018 R_☉ (these errors do not include uncertainties in the stellar models). We rule out the possibility that the transits result from an astrophysical false positive by first identifying the subset of stellar blends that reproduce the precise shape of the light curve. Using the additional constraints from the measured color of the system, the absence of a secondary source in the high-resolution spectrum, and the absence of a secondary source in the adaptive optics imaging, we conclude that the planetary scenario is more than three orders of magnitude more likely than a blend. The blend scenario is independently disfavored by the achromaticity of the transit: we measure a transit depth with Spitzer at 4.5 μm of 547^(+113)_(–110) ppm, consistent with the depth measured in the Kepler optical bandpass of 567 ± 6 ppm (corrected for stellar limb darkening). We determine a physical radius of the planet Kepler-19b of R_p = 2.209 ± 0.048 R_⊕; the uncertainty is dominated by uncertainty in the stellar parameters. From radial velocity observations of the star, we find an upper limit on the planet mass of 20.3 M_⊕, corresponding to a maximum density of 10.4 g cm^(–3). We report a significant sinusoidal deviation of the transit times from a predicted linear ephemeris, which we conclude is due to an additional perturbing body in the system. We cannot uniquely determine the orbital parameters of the perturber, as various dynamical mechanisms match the amplitude, period, and shape of the transit timing signal and satisfy the host star's radial velocity limits. However, the perturber in these mechanisms has a period ≾ 160 days and mass ≾ 6 M_(Jup), confirming its planetary nature as Kepler-19c. We place limits on the presence of transits of Kepler-19c in the available Kepler data.

Item Type:Article
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Ballard, Sarah0000-0002-3247-5081
Ciardi, David R.0000-0002-5741-3047
Additional Information:© 2011 The American Astronomical Society. Received 2011 August 18; accepted 2011 September 5; published 2011 December 6. We thank the Spitzer team at IPAC and in particular Nancy Silbermann for scheduling the Spitzer observations of this program. This work is based 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. Support for this work was provided by NASA through an award issued by JPL/Caltech. This work is also based on observations made with Kepler, which was competitively selected as the tenth Discovery mission. Funding for this mission is provided by NASA’s Science Mission Directorate. The authors thank the many people who generously gave so much of their time to make this mission a success. 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 Observatory was made possible by the generous financial support of the W. M. Keck Foundation.
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
W. M. Keck FoundationUNSPECIFIED
Subject Keywords:eclipses; planetary systems; stars: individual (Kepler-19, KOI-84, KIC 2571238)
Issue or Number:2
Record Number:CaltechAUTHORS:20120201-091404234
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Official Citation:The Kepler-19 System: A Transiting 2.2 R ⊕ Planet and a Second Planet Detected via Transit Timing Variations Sarah Ballard et al. 2011 ApJ 743 200
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:29057
Deposited By: Ruth Sustaita
Deposited On:01 Feb 2012 17:52
Last Modified:09 Mar 2020 13:18

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