Kepler-432: a red giant interacting with one of its two long period giant planets

Abstract

We report the discovery of Kepler-432b, a giant planet ($M_b=5.41_{-0.18}^{+0.32}{M}_{\mathrm{Jup}},R_b=1.145_{-0.039}^{+0.036}{R}_{\mathrm{Jup}}$) transiting an evolved star $(M_{\star }=1.32_{-0.07}^{+0.10}{M}_{\odot },R_{\star }=4.06_{-0.08}^{+0.12}{R}_{\odot })$ with an orbital period of $P_b=52.501129_{-0.000053}^{+0.000067}$ 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; $M_c\sin i_c=2.43_{-0.24}^{+0.22}{M}_{\mathrm{Jup}},P_c=406.2_{-2.5}^{+3.9}$ days), and adaptive optics imaging revealed a nearby (0\farcs87), faint companion (Kepler-432B) that is a physically bound M dwarf. The host star exhibits high signal-to-noise 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.

22 pages, 19 figures, 5 tables. Accepted to ApJ on Jan 24, 2015 (submitted Nov 11, 2014). Updated with minor changes to match published version

References in corpus (30)

• Improving PARSEC models for very low mass stars
• ADIPLS -- the Aarhus adiabatic oscillation package
• Tidal Evolution of Close-in Extra-Solar Planets
• Correcting stellar oscillation frequencies for near-surface effects
• Three regimes of extrasolar planets inferred from host star metallicities
• ASTEC -- the Aarhus STellar Evolution Code
• Retired A Stars and Their Companions: Exoplanets Orbiting Three Intermediate-Mass Subgiants
• Kepler constraints on planets near hot Jupiters
• Modeling Kepler transit light curves as false positives: Rejection of blend scenarios for Kepler-9, and validation of Kepler-9d, a super-Earth-size planet in a multiple system
• Planets around evolved intermediate-mass stars. I. Two substellar companions in the open clusters NGC 2423 and NGC 4349
• Hot Jupiters from Coplanar High-eccentricity Migration
• Radius determination of solar-type stars using asteroseismology: What to expect from the Kepler mission
• A precise asteroseismic age and radius for the evolved Sun-like star KIC 11026764
• The Photoeccentric Effect and Proto-Hot Jupiters I. Measuring photometric eccentricities of individual transiting planets
• Automated preparation of Kepler time series of planet hosts for asteroseismic analysis
• Oscillating K giants with the WIRE satellite: determination of their asteroseismic masses
• Determination of Three-dimensional Spin-orbit Angle with Joint Analysis of Asteroseismology, Transit Lightcurve, and the Rossiter-McLaughlin Effect: Cases of HAT-P-7 and Kepler-25
• On the diversity of magnetic interactions in close-in star-planet systems
• The properties of planets around giant stars
• A Misaligned Prograde Orbit for Kepler-13 Ab via Doppler Tomography
• On the tidal origin of hot Jupiter stellar obliquity trends
• Tidal Dissipation and Obliquity Evolution in Hot Jupiter Systems
• Radial Velocity Observations and Light Curve Noise Modeling Confirm That Kepler-91b is a Giant Planet Orbiting a Giant Star
• Transiting planets - lightcurve analysis for eccentric orbits
• The Challenge of Wide-Field Transit Surveys: The Case of GSC 01944-02289
• Bayesian priors for the eccentricity of transiting planets
• Kepler-432 b: a massive planet in a highly eccentric orbit transiting a red giant
• Using Stellar Densities to Evaluate Transiting Exoplanetary Candidates
• Radial velocity confirmation of Kepler-91 b. Additional evidence of its planetary nature using the Calar Alto/CAFE instrument
• Kepler-432 b: a massive warm Jupiter in a 52-day eccentric orbit transiting a giant star

Cited by in corpus (24)

• Stellar obliquities in exoplanetary systems
• The asteroseismic potential of TESS: exoplanet-host stars
• New planetary and EB candidates from Campaigns 1-6 of the K2 mission
• A Hot Saturn Orbiting An Oscillating Late Subgiant Discovered by TESS
• The Densities of Planets in Multiple Stellar Systems
• The Orbit and Mass of the Third Planet in the Kepler-56 System
• Measuring the Galactic Distribution of Transiting Planets with WFIRST
• Moderately Eccentric Warm Jupiters from Secular Interactions with Exterior Companions
• The Curious Case of KOI 4: Confirming Kepler's First Exoplanet
• The Pan-Pacific Planet Search. VIII. Complete results and the occurrence rate of planets around low-luminosity giants
• Automated approach to measure stellar inclinations: validation through large-scale measurements on the red giant branch
• Updated Catalog of Kepler Planet Candidates: Focus on Accuracy and Orbital Periods
• TESS Giants Transiting Giants III: An eccentric warm Jupiter supports a period-eccentricity relation for giant planets transiting evolved stars
• Synergies between Asteroseismology and Exoplanetary Science
• Qatar Exoplanet Survey: Qatar-8b, 9b and 10b --- A Hot Saturn and Two Hot Jupiters
• HD 76920b pinned down: a detailed analysis of the most eccentric planetary system around an evolved star
• The discovery of a planetary candidate around the evolved low-mass Kepler giant star HD 175370
• TESS Giants Transiting Giants V -- Two hot Jupiters orbiting red-giant hosts
• Occurrence rate of hot Jupiters orbiting red giant stars
• Gemini-GRACES high-quality spectra of Kepler evolved stars with transiting planets I. Detailed characterization of multi-planet systems Kepler-278 and Kepler-391
• Obliquities of Exoplanet Host Stars from Precise Distances and Stellar Angular Diameters
• A Close-in Planet Orbiting Giant Star HD 167768
• A simple model to describe intrinsic stellar noise for exoplanet detection around red giants
• Companions to Kepler giant stars: A long-period eccentric substellar companion to KIC 3526061 and a stellar companion to HD 187878