Planet Hunters VII. Discovery of a New Low-Mass, Low-Density Planet (PH3 c) Orbiting Kepler-289 with Mass Measurements of Two Additional Planets (PH3 b and d)

Abstract

We report the discovery of one newly confirmed planet ($P=66.06$ days, $R_{\mathrm{P}}=2.68\pm 0.17R_{\oplus }$) and mass determinations of two previously validated Kepler planets, Kepler-289 b ($P=34.55$ days, $R_{\mathrm{P}}=2.15\pm 0.10R_{\oplus }$) and Kepler-289-c ($P=125.85$ days, $R_{\mathrm{P}}=11.59\pm 0.10R_{\oplus }$), through their transit timing variations (TTVs). We also exclude the possibility that these three planets reside in a $1:2:4$ Laplace resonance. The outer planet has very deep ($\sim 1.3$), high signal-to-noise transits, which puts extremely tight constraints on its host star's stellar properties via Kepler's Third Law. The star PH3 is a young ($\sim 1$ Gyr as determined by isochrones and gyrochronology), Sun-like star with $M_{\ast }=1.08\pm 0.02M_{\odot }$, $R_{\ast }=1.00\pm 0.02R_{\odot }$, and $T_{\mathrm{eff}}=5990\pm 38$ K. The middle planet's large TTV amplitude ($\sim 5$ hours) resulted either in non-detections or inaccurate detections in previous searches. A strong chopping signal, a shorter period sinusoid in the TTVs, allows us to break the mass-eccentricity degeneracy and uniquely determine the masses of the inner, middle, and outer planets to be $M=7.3\pm 6.8M_{\oplus }$, $4.0\pm 0.9M_{\oplus }$, and $M=132\pm 17M_{\oplus }$, which we designate PH3 b, c, and d, respectively. Furthermore, the middle planet, PH3 c, has a relatively low density, $\rho =1.2\pm 0.3$ g/cm${}^3$ for a planet of its mass, requiring a substantial H/He atmosphere of $2.1_{-0.3}^{+0.8}$ by mass, and joins a growing population of low-mass, low-density planets.

arXiv comment21 pages, 10 figures, 5 tables, accepted into ApJ

References in corpus (70)

• emcee: The MCMC Hammer
• The Seventh Data Release of the Sloan Digital Sky Survey
• PARSEC: stellar tracks and isochrones with the PAdova and TRieste Stellar Evolution Code
• Direct Imaging of Multiple Planets Orbiting the Star HR 8799
• The Dartmouth Stellar Evolution Database
• Galaxy Zoo : Morphologies derived from visual inspection of galaxies from the Sloan Digital Sky Survey
• Planetary Candidates Observed by Kepler, III: Analysis of the First 16 Months of Data
• Characteristics of planetary candidates observed by Kepler, II: Analysis of the first four months of data
• Planetary Radii across Five Orders of Magnitude in Mass and Stellar Insolation: Application to Transits
• Efficient, uninformative sampling of limb darkening coefficients for two-parameter laws
• Ages for illustrative field stars using gyrochronology: viability, limitations and errors
• DHP Framework: Digital Health Passports Using Blockchain -- Use case on international tourism during the COVID-19 pandemic
• On detecting terrestrial planets with timing of giant planet transits
• A super-Earth transiting a nearby low-mass star
• Galaxy Zoo 1 : Data Release of Morphological Classifications for nearly 900,000 galaxies
• EXOFAST: A fast exoplanetary fitting suite in IDL
• Architecture of Kepler's Multi-transiting Systems: II. New investigations with twice as many candidates
• Understanding the Mass-Radius Relation for Sub-Neptunes: Radius as a Proxy for Composition
• A Closely-Packed System of Low-Mass, Low-Density Planets Transiting Kepler-11
• Kepler Eclipsing Binary Stars. I. Catalog and Principal Characterization of 1879 Eclipsing Binaries in the First Data Release
• Validation of Kepler's Multiple Planet Candidates. III: Light Curve Analysis & Announcement of Hundreds of New Multi-planet Systems
• Improving the Efficiency of Markov Chain Monte Carlo for Analyzing the Orbits of Extrasolar Planets
• Revised Stellar Properties of Kepler Targets for the Quarter 1-16 Transit Detection Run
• Kepler Eclipsing Binary Stars. II. 2165 Eclipsing Binaries in the Second Data Release
• The Exoplanet Orbit Database
• Kepler-36: A Pair of Planets with Neighboring Orbits and Dissimilar Densities
• Extracting Planet Mass and Eccentricity From TTV data
• Improved spectroscopic parameters for transiting planet hosts
• Parameter Estimation from Time-Series Data with Correlated Errors: A Wavelet-Based Method and its Application to Transit Light Curves
• A Framework for Characterizing the Atmospheres of Low-Mass Low-Density Transiting Planets
• The Lick-Carnegie Exoplanet Survey: A Uranus-mass Fourth Planet for GJ 876 in an Extrasolar Laplace Configuration
• Orbital perturbations on transiting planets: A possible method to measure stellar quadrupoles and to detect Earth-mass planets
• Formation and Structure of Low Density Exo-Neptunes
• Transit timing effects due to an exomoon
• A Planetary Companion to the Nearby M4 Dwarf, Gliese 876
• Transit Timing Observations from Kepler: IV. Confirmation of 4 Multiple Planet Systems by Simple Physical Models
• A Detailed Model Grid for Solid Planets from 0.1 through 100 Earth Masses
• Validation of Kepler's Multiple Planet Candidates. II: Refined Statistical Framework and Descriptions of Systems of Special Interest
• Stellar Rotation Periods of the Kepler Objects of Interest: A Dearth of Close-in Planets around Fast Rotators
• Planetary Candidates Observed by Kepler IV: Planet Sample From Q1-Q8 (22 Months)
• Quantitatively Assessing the Role of Clouds in the Transmission Spectrum of GJ 1214b
• Planet Hunters: A Transiting Circumbinary Planet in a Quadruple Star System
• Bulk Composition of GJ 1214b and other sub-Neptune exoplanets
• Very Low-Density Planets around Kepler-51 Revealed with Transit Timing Variations and an Anomaly Similar to a Planet-Planet Eclipse Event
• Two Earth-sized planets orbiting Kepler-20
• Transit Timing Observations from Kepler: III. Confirmation of 4 Multiple Planet Systems by a Fourier-Domain Study of Anti-correlated Transit Timing Variations
• Transit Timing Observations from Kepler. VIII Catalog of Transit Timing Measurements of the First Twelve Quarters
• All Six Planets Known to Orbit Kepler-11 Have Low Densities
• The Detection and Characterization of a Nontransiting Planet by Transit Timing Variations
• KOI-142, the King of Transit Variations, is a Pair of Planets near the 2:1 Resonance
• TTVFast: An efficient and accurate code for transit timing inversion problems
• The Kepler-19 System: A Transiting 2.2 R_Earth Planet and a Second Planet Detected via Transit Timing Variations
• Planet Hunters: The First Two Planet Candidates Identified by the Public using the Kepler Public Archive Data
• Three Body Resonance Overlap in Closely Spaced Multiple Planet Systems
• Transit Analysis Package (TAP and autoKep): IDL Graphical User Interfaces for Extrasolar Planet Transit Photometry
• The Planetary System to KIC 11442793: A Compact Analogue to the Solar System
• Transit Timing Variation of Near-Resonance Planetary Pairs. II. Confirmation of 30 planets in 15 Multiple Planet Systems
• Using Transit Timing Observations to Search for Trojans of Transiting Extrasolar Planets
• KOI-152's Low Density Planets
• Capture of Irregular Satellites at Jupiter
• A possible architecture of the planetary system HR 8799
• An Independent Planet Search In The Kepler Dataset. II. An extremely low-density super-Earth mass planet around Kepler-87
• The Quasiperiodic Automated Transit Search Algorithm
• Planet Hunters. VI: An Independent Characterization of KOI-351 and Several Long Period Planet Candidates from the Kepler Archival Data
• Planet Hunters. V. A Confirmed Jupiter-Size Planet in the Habitable Zone and 42 Planet Candidates from the Kepler Archive Data
• Planet Hunters: Assessing the Kepler Inventory of Short Period Planets
• Detection of Potential Transit Signals in Sixteen Quarters of Kepler Mission Data
• Dynamical analysis of the Gliese-876 Laplace resonance
• Planet Hunters: New Kepler planet candidates from analysis of quarter 2
• Potential Biases in the Detection of Planetary Systems with Large Transit Timing Variations

Cited by in corpus (41)

• Probabilistic Forecasting of the Masses and Radii of Other Worlds
• SOPHIE velocimetry of Kepler transit candidates XVII. The physical properties of giant exoplanets within 400 days of period
• Probabilistic Mass-Radius Relationship for Sub-Neptune-Sized Planets
• Planetary Candidates Observed by Kepler. VII. The First Fully Uniform Catalog Based on The Entire 48 Month Dataset (Q1-Q17 DR24)
• Kepler Planet Masses and Eccentricities from TTV Analysis
• A generalized bayesian inference method for constraining the interiors of super Earths and sub-Neptunes
• Warm Jupiters are less lonely than hot Jupiters: close neighbours
• Secure TTV Mass Measurements: Ten Kepler Exoplanets between 3 and 8 Earth Masses with Diverse Densities and Incident Fluxes
• Measurement of planet masses with transit timing variations due to synodic "chopping" effects
• Discovery of a Third Transiting Planet in the Kepler-47 Circumbinary System
• Transit timing to first order in eccentricity
• Planet Hunters. VIII. Characterization of 41 Long-Period Exoplanet Candidates from Kepler Archival Data
• Numerical and Analytical Modelling of Transit Time Variations
• Revised Masses and Densities of the Planets around Kepler-10
• Planet Hunters TESS I: TOI 813, a subgiant hosting a transiting Saturn-sized planet on an 84-day orbit
• An Overabundance of Low-density Neptune-like Planets
• A Relationship Between Stellar Age and Spot Coverage
• Doppler Monitoring of five K2 Transiting Planetary Systems
• Masses for the seven planets in K2-32 and K2-233. Four diverse planets in resonant chain and the first young rocky worlds
• Doppler Monitoring of the WASP-47 Multiplanet System
• The K2-OjOS Project: New and revisited planets and candidates in K2 campaigns 5, 16, & 18
• Planet Hunters X: Searching for Nearby Neighbors of 75 Planet and Eclipsing Binary Candidates from the K2 Kepler Extended Mission
• Mass determination of the 1:3:5 near-resonant planets transiting GJ 9827 (K2-135)
• Following up the Kepler field: Masses of Targets for transit timing and atmospheric characterization
• K2-288Bb: A Small Temperate Planet in a Low-mass Binary System Discovered by Citizen Scientists
• TOI-1670 b and c: An Inner Sub-Neptune with an Outer Warm Jupiter Unlikely to have Originated from High-Eccentricity Migration
• TESS Observations of Kepler systems with Transit Timing Variations
• Updated Catalog of Kepler Planet Candidates: Focus on Accuracy and Orbital Periods
• Systematic Search for Rings around Kepler Planet Candidates: Constraints on Ring Size and Occurrence Rate
• K2-263b: A 50-day period sub-Neptune with a mass measurement using HARPS-N
• A Search for Lost Planets in the Kepler Multi-planet Systems and the Discovery of the Long-period, Neptune-sized Exoplanet Kepler-150 f
• TTV-determined Masses for Warm Jupiters and their Close Planetary Companions
• Constraining the Densities of the Three Kepler-289 Planets with Transit Timing Variations
• Hyades Member K2-136c: The Smallest Planet in an Open Cluster with a Precisely Measured Mass
• Assessing the Interior Structure of Terrestrial Exoplanets with Implications for Habitability
• Implications of an improved water equation of state for water-rich planets
• Searching the Entirety of Kepler Data. I. 17 New Planet Candidates Including 1 Habitable Zone World
• The Exoplanet Edge: Planets Don't Induce Observable TTVs with a Dominant TTV Period Faster than Half their Orbital Period
• Discovery and Characterization of Kepler-36b
• The Occurrence-weighted Median Planets Discovered by Transit Surveys Orbiting Solar-type Stars and Their Implications for Planet Formation and Evolution
• The Visual Survey Group: A Decade of Hunting Exoplanets and Unusual Stellar Events with Space-Based Telescopes