WASP-117b: a 10-day-period Saturn in an eccentric and misaligned orbit

Abstract

We report the discovery of WASP-117b, the first planet with a period beyond 10 days found by the WASP survey. The planet has a mass of $M_p=0.2755\pm 0.0089M_J$, a radius of $R_p=1.021_{-0.065}^{+0.076}{R}_J$ and is in an eccentric ($e=0.302\pm 0.023$), $10.02165\pm 0.00055$~d orbit around a main-sequence F9 star. The host star's brightness (V=10.15 mag) makes WASP-117 a good target for follow-up observations, and with a periastron planetary equilibrium temperature of $T_{eq}=1225_{-39}^{+36}$ K and a low planetary mean density (${\rho }_p=0.259_{-0.048}^{+0.054}{\rho }_J$) it is one of the best targets for transmission spectroscopy among planets with periods around 10 days. From a measurement of the Rossiter-McLaughlin effect, we infer a projected angle between the planetary orbit and stellar spin axes of $\beta =-44\pm 11$ deg, and we further derive an orbital obliquity of $\psi =69.6_{-4.1}^{+4.7}$ deg. Owing to the large orbital separation, tidal forces causing orbital circularization and realignment of the planetary orbit with the stellar plane are weak, having had little impact on the planetary orbit over the system lifetime. WASP-117b joins a small sample of transiting giant planets with well characterized orbits at periods above ~8 days.

To appear in A&A

References in corpus (8)

• Improved Age Estimation for Solar-Type Dwarfs Using Activity-Rotation Diagnostics
• Tidal Evolution of Close-in Extra-Solar Planets
• Efficient identification of exoplanetary transit candidates from SuperWASP light curves
• The Transit Light Curve Project. IX. Evidence for a Smaller Radius of the Exoplanet XO-3b
• CLES, Code Liegeois d'Evolution Stellaire
• A fast hybrid algorithm for exoplanetary transit searches
• Misaligned spin-orbit in the XO-3 planetary system?
• WASP-42 b and WASP-49 b: two new transiting sub-Jupiters

Cited by in corpus (22)

• Revisited Mass-Radius relations for exoplanets below 120 Earth masses
• Stellar obliquities in exoplanetary systems
• TESS Transit Timing of Hundreds of Hot Jupiters
• The EBLM Project IV. Spectroscopic orbits of over 100 eclipsing M dwarfs masquerading as transiting hot-Jupiters
• Rossiter--McLaughlin models and their effect on estimates of stellar rotation, illustrated using six WASP systems
• ExoClock Project III: 450 new exoplanet ephemerides from ground and space observations
• Gaia's potential for the discovery of circumbinary planets
• HAT-P-65b and HAT-P-66b: Two Transiting Inflated Hot Jupiters and Observational Evidence for the Re-Inflation of Close-In Giant Planets
• Revisiting the correlation between stellar activity and planetary surface gravity
• Warm Jupiters in TESS Full-Frame Images: A Catalog and Observed Eccentricity Distribution for Year 1
• Ephemeris refinement of 21 Hot Jupiter exoplanets with high timing uncertainties
• WASP-104b and WASP-106b: two transiting hot Jupiters in 1.75-day and 9.3-day orbits
• The well-aligned orbit of WASP-84b: evidence for disc migration
• Deriving stellar inclination of slow rotators using stellar activity
• Exoplanet Interior Retrievals: core masses and metallicities from atmospheric abundances
• Three Hot-Jupiters on the upper edge of the mass-radius distribution: WASP-177, WASP-181 and WASP-183
• Prospects from TESS and Gaia to constrain the flatness of planetary systems
• Detection limits of exoplanetary atmospheres with 2-m class telescopes
• TESS Timings of 31 Hot Jupiters with Ephemeris Uncertainties
• Precise Transit Photometry Using TESS II: Revisiting 28 Additional Transiting Systems With Updated Physical Properties
• The inflated, eccentric warm Jupiter TOI-4914 b orbiting a metal-poor star, and the hot Jupiters TOI-2714 b and TOI-2981 b
• Tentative Evidence for Transit Timing Variations of WASP-161b