Journal
ASTROPHYSICAL JOURNAL
Volume 803, Issue 2, Pages -Publisher
IOP PUBLISHING LTD
DOI: 10.1088/0004-637X/803/2/49
Keywords
asteroseismology; planets and satellites: dynamical evolution and stability; planets and satellites: formation; planets and satellites: gaseous planets; planet-star interactions; stars: individual (Kepler-432)
Categories
Funding
- NSF Graduate Research Fellowship [DGE-1051030]
- NASA's Kepler mission [NNX11AB99A]
- Smithsonian Astrophysical Observatory
- Australian Research Council [DEI40101364]
- NASA [NNX14AB92G]
- NASA Origins of Solar Systems Program [NNX13A124G]
- Danish National Research Foundation [DNRF106]
- ASTERISK project (ASTERoseismic Investigations with SONG and Kepler) - European Research Council [267864]
- European Research Council under the European Community's Seventh Framework Programme [338251]
- Robert Martin Ayers Sciences Fund
- National Aeronautics and Space Administration
- National Science Foundation
- University of Massachusetts
- Infrared Processing and Analysis Center/California Institute of Technology
- STFC [ST/M00077X/1] Funding Source: UKRI
- Science and Technology Facilities Council [ST/M00077X/1] Funding Source: researchfish
- NASA [149453, NNX11AB99A] Funding Source: Federal RePORTER
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We report the discovery of Kepler-432b, a giant planet ( M-b = 5.41(-0.18)(+0.32) M-Jup R-b = 1.145(-0.039)(+0.036),R-Jup) transiting an evolved star (M-* = 1.32(-0.07)(+0.10) M-circle dot R-* 4.06(-0.08)(+0.12) R-circle dot) with an orbital period of Pb = 52.501129(-0.000053)(+0.000067) days. Radial velocities (RVs) reveal that Kepler-432b orbits its parent star with an eccentricity of e = 0.5134(-0.0089)(+0.0098) , which we also measure independently with asterodensity profiling (AP; e = 0.507(-0.114)(+0.039)), thereby confirming the validity of AP on this particular evolved star. The well-determined planetary properties and unusually large mass also make this planet an important benchmark for theoretical models of super-Jupiter formation. Long-term RV monitoring detected the presence of a non-transiting outer planet (Kepler-432c; = M-c sin i(c) = 2.43(-0.24)(+0.22) M-Jup, P-c = 406.2(-2.5)(+3.9) days), and adaptive optics imaging revealed a nearby (0.'' 87), faint companion (Kepler-432B) that is a physically bound M dwarf. The host star exhibits high signal-to-noise ratio asteroseismic oscillations, which enable precise measurements of the stellar mass, radius, and age. Analysis of the rotational splitting of the oscillation modes additionally reveals the stellar spin axis to be nearly edge-on, which suggests that the stellar spin is likely well aligned with the orbit of the transiting planet. Despite its long period, the obliquity of the 52.5 day orbit may have been shaped by star-planet interaction in a manner similar to hot Jupiter systems, and we present observational and theoretical evidence to support this scenario. Finally, as a short-period outlier among giant planets orbiting giant stars, study of Kepler-432b may help explain the distribution of massive planets orbiting giant stars interior to 1 AU.
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