Kepler-77b: a very low albedo, Saturn-mass transiting planet around a metal-rich solar-like star

Abstract

We report the discovery of Kepler-77b (alias KOI-127.01), a Saturn-mass transiting planet in a 3.6-day orbit around a metal-rich solar-like star. We combined the publicly available Kepler photometry (quarters 1-13) with high-resolution spectroscopy from the Sandiford@McDonald and FIES@NOT spectrographs. We derived the system parameters via a simultaneous joint fit to the photometric and radial velocity measurements. Our analysis is based on the Bayesian approach and is carried out by sampling the parameter posterior distributions using a Markov chain Monte Carlo simulation. Kepler-77b is a moderately inflated planet with a mass of Mp=0.430+/-0.032 Mjup, a radius of Rp=0.960+/-0.016 Rjup, and a bulk density of 0.603+/-0.055 g/cm^3. It orbits a slowly rotating (P=36+/-6 days) G5V star with M*=0.95+/-0.04 Msun, R*=0.99+/-0.02 Rsun, Teff=5520+/-60 K, [M/H]=0.20+/-0.05, that has an age of 7.5+/-2.0 Gyr. The lack of detectable planetary occultation with a depth higher than about 10 ppm implies a planet geometric and Bond albedo of Ag<0.087+/-0.008 and Ab<0.058+/-0.006, respectively, placing Kepler-77b among the gas-giant planets with the lowest albedo known so far. We found neither additional planetary transit signals nor transit-timing variations at a level of about 0.5 minutes, in accordance with the trend that close-in gas giant planets seem to belong to single-planet systems. The 106 transits observed in short-cadence mode by Kepler for nearly 1.2 years show no detectable signatures of the planet's passage in front of starspots. We explored the implications of the absence of detectable spot-crossing events for the inclination of the stellar spin-axis, the sky-projected spin-orbit obliquity, and the latitude of magnetically active regions.

13 pages, 10 figures, 3 tables. Accepted for publication in A&A. This version includes referee comments. Planet's name changed from KOI-127b to Kepler-77b

References in corpus (9)

• A grid of MARCS model atmospheres for late-type stars I. Methods and general properties
• DHP Framework: Digital Health Passports Using Blockchain -- Use case on international tourism during the COVID-19 pandemic
• KEPLER's First Rocky Planet: Kepler-10b
• Measuring the rotation period distribution of field M-dwarfs with Kepler
• Alignment of the stellar spin with the orbits of a three-planet system
• A sub-Mercury-sized exoplanet
• The Very Low Albedo of an Extrasolar Planet: MOST Spacebased Photometry of HD 209458
• SOPHIE velocimetry of Kepler transit candidates VII. A false-positive rate of 35% for Kepler close-in giant exoplanet candidates
• Transiting exoplanets from the CoRoT space mission XIV. CoRoT-11b: a transiting massive "hot-Jupiter" in a prograde orbit around a rapidly rotating F-type star

Cited by in corpus (36)

• Probabilistic Forecasting of the Masses and Radii of Other Worlds
• Revised Stellar Properties of Kepler Targets for the Q1-17 (DR25) Transit Detection Run
• SOPHIE velocimetry of Kepler transit candidates XVII. The physical properties of giant exoplanets within 400 days of period
• Limb darkening and exoplanets: testing stellar model atmospheres and identifying biases in transit parameters
• PyTransit: Fast and Easy Exoplanet Transit Modelling in Python
• Warm Jupiters are less lonely than hot Jupiters: close neighbours
• Exoplanets around Low-mass Stars Unveiled by K2
• The transiting multi-planet system HD3167: a 5.7 MEarth Super-Earth and a 8.3 MEarth mini-Neptune
• 44 Validated Planets from K2 Campaign 10
• The GAPS Programme with HARPS-N@TNG V. A comprehensive analysis of the XO-2 stellar and planetary systems
• Three Small Super-Earths Transiting the nearby star GJ 9827
• Super-Earth of 8 Mearth in a 2.2-day orbit around the K5V star K2-216
• Kepler423b: a half-Jupiter mass planet transiting a very old solar-like star
• Discovery of Two New Thermally Bloated Low-Mass White Dwarfs Among the Kepler Binaries
• HD 89345: a bright oscillating star hosting a transiting warm Saturn-sized planet observed by K2
• Kepler-424 b: A "Lonely" Hot Jupiter That Found A Companion
• Time variation of Kepler transits induced by stellar spots - a way to distinguish between prograde and retrograde motion. II. Application to KOIs
• K2-290: a warm Jupiter and a mini-Neptune in a triple-star system
• The stellar obliquity, planet mass, and very low albedo of Qatar-2 from K2 Photometry
• Tidally Distorted Exoplanets: Density Corrections for Short-Period Hot-Jupiters based solely on Observable Parameters
• K2-98 b: A 32-M${}_{\oplus }$ Neptune-sized planet in a 10-day orbit transiting an F8 star
• Searching for reflected light from $\tau$ Bootis b with high-resolution ground-based spectroscopy: Approaching the $10^{-5}$ contrast barrier
• Kepler-539: a young extrasolar system with two giant planets on wide orbits and in gravitational interaction
• K2-140b and K2-180b - Characterization of a hot Jupiter and a mini-Neptune from the K2 mission
• Probing a $r^{-n}$ modification of the Newtonian potential with Exoplanets
• The GAPS Programme with HARPS-N@TNG VI: The Curious Case of TrES-4b
• Confirmation of an exoplanet using the transit color signature: Kepler-418b, a blended giant planet in a multiplanet system
• The HD 93963 A transiting system: A 1.04d super-Earth and a 3.65 d sub-Neptune discovered by TESS and CHEOPS
• A ground-based NUV secondary eclipse observation of KELT-9b
• CoRoT 223992193: Investigating the variability in a low-mass, pre-main sequence eclipsing binary with evidence of a circumbinary disk
• Hundreds of TESS exoplanets might be larger than we thought
• The multi-planet system TOI-421 -- A warm Neptune and a super puffy mini-Neptune transiting a G9 V star in a visual binary
• Weighing stars from birth to death: mass determination methods across the HRD
• Five new eclipsing binaries with low-mass companions
• An Investigation into Exoplanet Transits and Uncertainties
• Transit modelling of selected Kepler systems