Revisiting the Architecture of the KOI-89 System

Abstract

While high stellar obliquities observed in exoplanetary systems may be attributed to processes that tilt the planetary orbits, it is also possible that they reflect misalignments between protoplanetary disks and stellar spins. This latter hypothesis predicts the presence of co-planar multi-planetary systems misaligned with their central stars. Here we re-evaluate the evidence of such an architecture that has been claimed for the KOI-89 system. KOI-89 is an early-type star with one validated transiting planet KOI-89.01/Kepler-462b (period 84.7 days, radius $3.0R_{\oplus }$) and one transiting planet candidate KOI-89.02 (period 207.6 days, radius $4.0R_{\oplus }$), where the latter exhibits transit timing variations (TTVs). A previous modeling of the stellar gravity-darkening effect in the transit light curves inferred a high stellar obliquity of $\approx 70^{\circ }$. We perform a photodynamical modeling of the Kepler transit light curves, and use the resulting constraints on the orbital configuration and transit times to update the gravity-darkened transit model. As a result, we find no firm evidence for gravity darkening effect in the transit shapes and conclude that stellar obliquity is not constrained by the data. Given evidence for low orbital eccentricities from the dynamical analysis, the system architecture can thus be consistent with many other multi-transiting systems with flat, near-circular orbits aligned with the stellar spin. We find that the TTVs imparted on its neighbor imply that KOI-89.01 has a mass $\gtrsim 20M_{\oplus }$. This would render it one of the densest known sub-Neptunes, mostly composed of a solid core. Lower masses are possible if the TTVs are instead due to an unseen third planet.

arXiv commentaccepted for publication in AJ

References in corpus (102)

• Astropy: A Community Python Package for Astronomy
• Gaia Data Release 2. Summary of the contents and survey properties
• The Astropy Project: Building an inclusive, open-science project and status of the v2.0 core package
• Modules for Experiments in Stellar Astrophysics (MESA)
• Binary companions of evolved stars in APOGEE DR14: Search method and catalog of ~5,000 companions
• Modules for Experiments in Stellar Astrophysics (MESA): Giant Planets, Oscillations, Rotation, and Massive Stars
• Modules for Experiments in Stellar Astrophysics (MESA): Binaries, Pulsations, and Explosions
• MultiNest: an efficient and robust Bayesian inference tool for cosmology and particle physics
• MESA Isochrones and Stellar Tracks (MIST). I: Solar-Scaled Models
• Analytic Lightcurves for Planetary Transit Searches
• A new extensive library of PHOENIX stellar atmospheres and synthetic spectra
• MESA Isochrones and Stellar Tracks (MIST) 0: Methods for the construction of stellar isochrones
• Estimating distances from parallaxes IV: Distances to 1.33 billion stars in Gaia Data Release 2
• Multimodal nested sampling: an efficient and robust alternative to MCMC methods for astronomical data analysis
• X-ray spectral modelling of the AGN obscuring region in the CDFS: Bayesian model selection and catalogue
• Shrinking binary and planetary orbits by Kozai cycles with tidal friction
• REBOUND: An open-source multi-purpose N-body code for collisional dynamics
• batman: BAsic Transit Model cAlculatioN in Python
• Fast and scalable Gaussian process modeling with applications to astronomical time series
• The Revised TESS Input Catalog and Candidate Target List
• Importance Nested Sampling and the MultiNest Algorithm
• Dynamical Outcomes of Planet-Planet Scattering
• Efficient, uninformative sampling of limb darkening coefficients for two-parameter laws
• The First Data Release (DR1) of the LAMOST general survey
• Hot Stars with Hot Jupiters Have High Obliquities
• IAS15: A fast, adaptive, high-order integrator for gravitational dynamics, accurate to machine precision over a billion orbits
• Obliquities of Hot Jupiter host stars: Evidence for tidal interactions and primordial misalignments
• Probabilistic Forecasting of the Masses and Radii of Other Worlds
• Growth Model Interpretation of Planet Size Distribution
• Dynamical Origin of Extrasolar Planet Eccentricity Distribution
• Homogeneous studies of transiting extrasolar planets. IV. Thirty systems with space-based light curves
• Hot Jupiters from Secular Planet--Planet Interactions
• The California Kepler Survey VII. Precise Planet Radii Leveraging Gaia DR2 Reveal the Stellar Mass Dependence of the Planet Radius Gap
• Validation of Kepler's Multiple Planet Candidates. III: Light Curve Analysis & Announcement of Hundreds of New Multi-planet Systems
• The Role of Core Mass in Controlling Evaporation: the Kepler Radius Distribution and the Kepler-36 Density Dichotomy
• Galactic Reddening in 3D from Stellar Photometry - An Improved Map
• Kepler-36: A Pair of Planets with Neighboring Orbits and Dissimilar Densities
• Chaotic star formation and the alignment of stellar rotation with disc and planetary orbital axes
• Extracting Planet Mass and Eccentricity From TTV data
• STARRY: Analytic Occultation Light Curves
• Revised Radii of Kepler Stars and Planets Using Gaia Data Release 2
• Stellar Spin-Orbit Misalignment in a Multiplanet System
• Revised Stellar Properties of Kepler Targets for the Q1-17 (DR25) Transit Detection Run
• Orbital perturbations on transiting planets: A possible method to measure stellar quadrupoles and to detect Earth-mass planets
• Evidence of Possible Spin-Orbit Misalignment Along the Line of Sight in Transiting Exoplanet Systems
• Gravity darkening in rotating stars
• About 30% of Sun-like Stars Have Kepler-like Planetary Systems: A Study of their Intrinsic Architecture
• Stellar Diameters and Temperatures III. Main Sequence A, F, G, & K Stars: Additional high-precision measurements and empirical relations
• A Plateau in the Planet Population Below Twice the Size of Earth
• Densities and Eccentricities of 139 Kepler Planets from Transit Time Variations
• CERES: A Set of Automated Routines for Echelle Spectra
• Alignment of the stellar spin with the orbits of a three-planet system
• Misaligned spin-orbit in the XO-3 planetary system?
• Asteroseismic determination of obliquities of the exoplanet systems Kepler-50 and Kepler-65
• The Oblique Orbit of the Super-Neptune HAT-P-11b
• Low stellar obliquities in compact multiplanet systems
• TTVFast: An efficient and accurate code for transit timing inversion problems
• Analytic Planetary Transit Light Curves and Derivatives for Stars with Polynomial Limb Darkening
• Star-Disc-Binary Interactions in Protoplanetary Disc Systems and Primordial Spin-Orbit Misalignments
• Orbital misalignment of the Neptune-mass exoplanet GJ 436b with the spin of its cool star
• Photometric Amplitude Distribution of Stellar Rotation of Kepler KOIs-Indication for Spin-Orbit Alignment of Cool Stars and High Obliquity for Hot Stars
• Transit Lightcurves of Extrasolar Planets Orbiting Rapidly-Rotating Stars
• Internal Gravity Waves Modulate the Apparent Misalignment of Exoplanets around Hot Stars
• Activity indicators and stellar parameters of the Kepler targets. An application of the ROTFIT pipeline to LAMOST-Kepler stellar spectra
• Architectures of Exoplanetary Systems. I: A Clustered Forward Model for Exoplanetary Systems around Kepler's FGK Stars
• Magnetic and Gravitational Disk-Star Interactions: An Interdependence of PMS Stellar Rotation Rates and Spin-Orbit Misalignments
• The Turbulent Origin of Spin-Orbit Misalignment in Planetary Systems
• A remnant planetary core in the hot-Neptune desert
• Planet-Planet Eclipse and the Rossiter-McLaughlin Effect of a Multiple Transiting System: Joint Analysis of the Subaru Spectroscopy and the Kepler Photometry
• The High Eccentricity of the Planet Around 16 Cyg B
• Transit Timing Variation of Near-Resonance Planetary Pairs. II. Confirmation of 30 planets in 15 Multiple Planet Systems
• TESS Hunt for Young and Maturing Exoplanets (THYME) III: a two-planet system in the 400 Myr Ursa Major Group
• Evidence for a high mutual inclination between the cold Jupiter and transiting super Earth orbiting $\pi$ Men
• ZASPE: A Code to Measure Stellar Atmospheric Parameters and their Covariance from Spectra
• On the alignment of debris disks and their host stars' rotation axis -implications for spin-orbit misalignment in exoplanetary systems
• Early Excitation of Spin-Orbit Misalignments in Close-in Planetary Systems
• Larger mutual inclinations for the shortest-period planets
• Hiding Planets Behind a Big Friend: Mutual Inclinations of Multi-Planet Systems with External Companions
• Magnetic Origins of the Stellar Mass-Obliquity Correlation in Planetary Systems
• A precise architecture characterization of the $\pi$ Men planetary system
• Alignment in star-debris disc systems seen by Herschel
• Spin-Orbit Angles of Kepler-13Ab and HAT-P-7b from Gravity-Darkened Transit Light Curves
• Kepler-108: A Mutually Inclined Giant Planet System
• Planet Formation in Disks with Inclined Binary Companions: Can Primordial Spin-Orbit Misalignment be Produced?
• Nearly Polar orbit of the sub-Neptune HD3167 c: Constraints on a multi-planet system dynamical history
• Stellar Spin-Orbit Alignment for Kepler-9, a Multi-transiting Planetary system with Two Outer Planets Near 2:1 Resonance
• Dynamically hot Super-Earths from outer giant planet scattering
• The Orbit and Mass of the Third Planet in the Kepler-56 System
• Evidence for Spin-orbit Alignment in the TRAPPIST-1 System
• The Dynamics of the Multi-planet System Orbiting Kepler-56
• A low stellar obliquity for WASP-47, a compact multiplanet system with a hot Jupiter and an ultra-short period planet
• A significant mutual inclination between the planets within the $\pi$ Mensae system
• Mutual Orbital Inclinations Between Cold Jupiters and Inner Super-Earths
• The warm Neptunes around HD 106315 have low stellar obliquities
• Outer-planet scattering can gently tilt an inner planetary system
• Star-disc (mis-)alignment in Rho Oph and Upper Sco: insights from spatially resolved disc systems with K2 rotation periods
• The misaligned orbit of the Earth-sized planet Kepler-408b
• Star-disk alignment in the protoplanetary disks: SPH simulation of the collapse of turbulent molecular cloud cores
• Gravity-Darkening Analysis of Misaligned Hot Jupiter MASCARA-4 b
• The Magellan/PFS Exoplanet Search: A 55-day period dense Neptune transiting the bright ($V=8.6$) star HD 95338
• Robustly detecting changes in warm Jupiters' transit impact parameters
• Constraints on the Obliquities of Kepler Planet-Hosting Stars

Cited by in corpus (6)

• Stellar obliquities in exoplanetary systems
• Multiplicity Boost Of Transit Signal Classifiers: Validation of 69 New Exoplanets Using The Multiplicity Boost of ExoMiner
• Hyades Member K2-136c: The Smallest Planet in an Open Cluster with a Precisely Measured Mass
• HD 56414 b: A Warm Neptune Transiting an A-type Star
• The GALAH Survey: Improving our understanding of confirmed and candidate planetary systems with large stellar surveys
• Small and Close-In Planets are Uncommon Around A-type Stars