Determining Exoplanetary Oblateness Using Transit Depth Variations

Abstract

The measurement of an exoplanet's oblateness and obliquity provides insights into the planet's internal structure and formation history. Previous work using small differences in the shape of the transit light curve has been moderately successful, but was hampered by the small signal and extreme photometric precision required. The measurement of changes in transit depth, caused by the spin precession of an oblate planet, was proposed as an alternative method. Here, we present the first attempt to measure these changes. Using Kepler photometry, we examined the brown dwarf Kepler-39b and the warm Saturn Kepler-427b. We could not reliably constrain the oblateness of Kepler-39b. We find transit depth variations for Kepler-427b at $90.1\%$ significance ($1.65\sigma$) consistent with a precession period of $P_{\mathrm{prec}}=5.45_{-0.37}^{+0.46}\mathrm{years}$ and an oblateness, $f=0.19_{-0.16}^{+0.32}$. This oblateness is comparable to Solar System gas giants, and would raise questions about the dynamics and tidal synchronization of Kepler-427b.

20 pages, 14 figures, accepted for publication in AJ

References in corpus (29)

• emcee: The MCMC Hammer
• The Transiting Exoplanet Survey Satellite
• Analytic Lightcurves for Planetary Transit Searches
• The K2 Mission: Characterization and Early results
• SOPHIE velocimetry of Kepler transit candidates XVII. The physical properties of giant exoplanets within 400 days of period
• Probing the Interiors of Very Hot Jupiters Using Transit Light Curves
• Spin-Orbit Evolution Of Short-Period Planets
• Transit Timing Observations from Kepler. IX. Catalog of the Full Long-Cadence Data Set
• New constraints on Saturn's interior from Cassini astrometric data
• Kepler-63b: A Giant Planet in a Polar Orbit around a Young Sun-like Star
• Measuring the Oblateness and Rotation of Transiting Extrasolar Giant Planets
• How stellar activity affects the size estimates of extrasolar planets
• Constraining the Rotation Rate of Transiting Extrasolar Planets by Oblateness Measurements
• The Transit Light Curve Project. XIII. Sixteen Transits of the Super-Earth GJ 1214b
• A Preliminary Jupiter Model
• The Detectability of Transit Depth Variations due to Exoplanetary Oblateness and Spin Precession
• Observational biases in determining extrasolar planet eccentricities in single-planet systems
• Rotation periods and ages of solar analogs and solar twins revealed by the Kepler Mission
• Empirical Constraints on the Oblateness of an Exoplanet
• New values of gravitational moments J2 and J4 deduced from helioseismology
• Measurement of Spin-Orbit Misalignment and Nodal Precession for the Planet around Pre-Main-Sequence Star PTFO 8-8695 From Gravity Darkening
• Atmospheric Lensing and Oblateness Effects During an Extrasolar Planetary Transit
• Constraining the Oblateness of Kepler Planets
• Kepler423b: a half-Jupiter mass planet transiting a very old solar-like star
• Improved parameters of seven Kepler giant companions characterized with SOPHIE and HARPS-N
• Investigation of systematic effects in Kepler data: Seasonal variations in the light curve of HAT-P-7b
• Variability of M giant stars based on Kepler photometry: general characteristics
• The Ratio of Retrograde to Prograde Orbits: A Test for Kuiper Belt Binary Formation Theories
• Characterization of the four new transiting planets KOI-188b, KOI-195b, KOI-192b, and KOI-830b

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• Boundary Layer Circumplanetary Accretion: How Fast Could an Unmagnetized Planet Spin Up Through Its Disk?
• On the Effects of Planetary Oblateness on Exoplanet Studies
• Detecting Planetary Oblateness in the Era of JWST: A Case Study of Kepler-167e
• Constraining the oblateness of transiting planets with photometry and spectroscopy
• Exploring Exoplanet Dynamics with JWST: Tides, Rotation, Rings, and Moons
• Planetary Obliquity Excitation Through Pre-Main Sequence Stellar Evolution