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Published November 10, 2014 | Submitted + Published
Journal Article Open

Planet Hunters. VII. Discovery of a New Low-mass, Low-density Planet (PH3 C) Orbiting Kepler-289 with Mass Measurements of Two Additional Planets (PH3 B and D)

Abstract

We report the discovery of one newly confirmed planet (P = 66.06 days, R_P = 2.68 ± 0.17 R_⊕) and mass determinations of two previously validated Kepler planets, Kepler-289 b (P = 34.55 days, R_P = 2.15 ± 0.10 R_⊕) and Kepler-289-c (P = 125.85 days, R_P = 11.59 ± 0.10 R_⊕), through their transit timing variations (TTVs). We also exclude the possibility that these three planets reside in a 1:2:4 Laplace resonance. The outer planet has very deep (~1.3%), high signal-to-noise transits, which puts extremely tight constraints on its host star's stellar properties via Kepler's Third Law. The star PH3 is a young (~1 Gyr as determined by isochrones and gyrochronology), Sun-like star with M_* = 1.08 ± 0.02 M_☉, R_* = 1.00 ± 0.02 R_☉, and T_(eff) = 5990 ± 38 K. The middle planet's large TTV amplitude (~5 hr) resulted either in non-detections or inaccurate detections in previous searches. A strong chopping signal, a shorter period sinusoid in the TTVs, allows us to break the mass-eccentricity degeneracy and uniquely determine the masses of the inner, middle, and outer planets to be M = 7.3 ± 6.8 M_⊕, 4.0 ± 0.9 M_⊕, and M = 132 ± 17 M_⊕, which we designate PH3 b, c, and d, respectively. Furthermore, the middle planet, PH3 c, has a relatively low density, ρ = 1.2 ± 0.3 g cm^(–3) for a planet of its mass, requiring a substantial H/He atmosphere of 2.1^(+0.8)_(-0.3)% by mass, and joins a growing population of low-mass, low-density planets.

Additional Information

© 2014 American Astronomical Society. Received 2014 July 18; accepted 2014 September 18; published 2014 October 28. The data presented in this paper are the result of the efforts of the PH volunteers, without whom thisworkwould not have been possible. Their contributions are individually acknowledged at http://www.planethunters.org/authors. The authors thank the PH volunteers who participated in identifying and analyzing the candidates presented in this paper. E.A. acknowledges funding by NSF Career grant AST 0645416; NASA Astrobiology Institutes Virtual Planetary Laboratory, supported by NASA under cooperative agreement NNH05ZDA001C; and NASA Origins of Solar Systems grant 12-OSS12-0011. K.M.D. acknowledges the support of an NSF Graduate Research Fellowship. D.F. acknowledges funding support for PlanetHunters.org from Yale University and support from the NASA Supplemental Outreach Award, 10-OUTRCH.210-0001 and the NASA ADAP12-0172. L.A.R. gratefully acknowledges support provided by NASA through Hubble Fellowship grant #HF-51313 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. K.S. gratefully acknowledges support from Swiss National Science Foundation Grant PP00P2_138979/1. M.E.S. is supported in part by an Academia Sinica postdoctoral fellowship. This research has made use of the Exoplanet Orbit Database and the Exoplanet Data Explorer at exoplanets.org. The Zooniverse is supported by The Leverhulme Trust and by the Alfred P. Sloan foundation. PH is supported in part by NASA JPL's PlanetQuest program. The Talk system used by PH was built during work supported by the NSF under grant No. DRL-0941610. We gratefully acknowledge the dedication and achievements of Kepler science team and all those who contributed to the success of the mission. We acknowledge use of public release data served by the NASA/IPAC/NExScI Star and Exoplanet Database, which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. This research has made use of NASA's Astrophysics Data System Bibliographic Services. This paper includes data collected by the Kepler spacecraft, and we gratefully acknowledge the entire Kepler mission team's efforts in obtaining and providing the light curves used in this analysis. Funding for the Kepler mission is provided by the NASA Science Mission directorate. Support for MAST for non-HST data is provided by the NASA Office of Space Science via grant NNX13AC07G and by other grants and contracts. Some of the data presented in this paper were obtained from the Mikulski Archive for Space Telescopes (MAST). STScI is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555. Support for MAST for non-HST data is provided by the NASA Office of Space Science via grant NNX13AC07G and by other grants and contracts. The data presented herein were partly 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.

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August 22, 2023
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