A High False Positive Rate for Kepler Planetary Candidates of Giant Stars using Asterodensity Profiling

Abstract

Asterodensity Profiling (AP) is a relatively new technique for studying transit light curves. By comparing the mean stellar density derived from the transit light curve to that found through some independent method, AP provides information on several useful properties such as orbital eccentricity and blended light. We present an AP survey of 41 Kepler Objects of Interest (KOIs), with a single transiting candidate, for which the target star's mean stellar density has been measured using asteroseismology. The ensemble distribution of the AP measurements for the 31 dwarf stars in our sample shows excellent agreement with the spread expected if the KOIs were genuine and have realistic eccentricities. In contrast, the same test for the 10 giants in our sample reveals significant incompatibility at 4$\sigma$ confidence. Whilst extreme eccentricities could be invoked, this hypothesis requires four of the KOIs to contact their host star at periastron passage, including the recently claimed confirmation of Kepler-91b. After carefully examining several hypotheses, we conclude that the most plausible explanation is that the transiting objects orbit a different star to that measured with asteroseismology - cases we define as false-positives. Based on the AP distribution, we estimate a false positive rate for Kepler's giant stars with a single transiting object of FPR$\simeq 70\pm 30$%.

11 pages, 5 figures, 2 tables. Accepted in ApJ

References in corpus (16)

• DHP Framework: Digital Health Passports Using Blockchain -- Use case on international tourism during the COVID-19 pandemic
• The Mass-Radius Relation for 65 Exoplanets Smaller than 4 Earth Radii
• The effect of red noise on planetary transit detection
• Validation of Kepler's Multiple Planet Candidates. III: Light Curve Analysis & Announcement of Hundreds of New Multi-planet Systems
• Revised Stellar Properties of Kepler Targets for the Quarter 1-16 Transit Detection Run
• Transit timing effects due to an exomoon
• Modeling Kepler transit light curves as false positives: Rejection of blend scenarios for Kepler-9, and validation of Kepler-9d, a super-Earth-size planet in a multiple system
• Validation of Kepler's Multiple Planet Candidates. II: Refined Statistical Framework and Descriptions of Systems of Special Interest
• Planetary Candidates Observed by Kepler IV: Planet Sample From Q1-Q8 (22 Months)
• The Photoeccentric Effect and Proto-Hot Jupiters I. Measuring photometric eccentricities of individual transiting planets
• Kepler-91b: a planet at the end of its life. Planet and giant host star properties via light-curve variations
• What asteroseismology can do for exoplanets: Kepler-410A b is a Small Neptune around a bright star, in an eccentric orbit consistent with low obliquity
• Surface Activity and Oscillation Amplitudes of Red Giants in Eclipsing Binaries
• Characterizing Distant Worlds with Asterodensity Profiling
• Using Stellar Densities to Evaluate Transiting Exoplanetary Candidates
• APOSTLE: Eleven Transit Observations of TrES-3b

Cited by in corpus (45)

• The Occurrence and Architecture of Exoplanetary Systems
• False positive probabilties for all Kepler Objects of Interest: 1284 newly validated planets and 428 likely false positives
• Revised Radii of Kepler Stars and Planets Using Gaia Data Release 2
• Eccentricity from transit photometry: small planets in Kepler multi-planet systems have low eccentricities
• Hot super-Earths stripped by their host stars
• The orbital eccentricity of small planet systems
• Hot Jupiters and Cool Stars
• Changing Phases of Alien Worlds: Probing Atmospheres of Kepler Planets with High-Precision Photometry
• They are Small Worlds After All: Revised Properties of Kepler M Dwarf Stars and their Planets
• The Gaia-Kepler Stellar Properties Catalog. II. Planet Radius Demographics as a Function of Stellar Mass and Age
• The asteroseismic potential of TESS: exoplanet-host stars
• Re-inflated Warm Jupiters Around Red Giants
• A Hot Saturn Orbiting An Oscillating Late Subgiant Discovered by TESS
• Kepler-432: a red giant interacting with one of its two long period giant planets
• Low False-Positive Rate of Kepler Candidates Estimated From A Combination Of Spitzer And Follow-Up Observations
• A novel method for identifying exoplanetary rings
• Kepler-432 b: a massive planet in a highly eccentric orbit transiting a red giant
• Giant planet occurrence within 0.2 AU of low-luminosity red giant branch stars with K2
• Kepler423b: a half-Jupiter mass planet transiting a very old solar-like star
• Adaptive Optics Images III: 87 Kepler Objects of Interest
• A Transiting Jupiter Analog
• The K2-ESPRINT Project V: a short-period giant planet orbiting a subgiant star
• The K2-HERMES Survey. I. Planet Candidate Properties from K2 Campaigns 1-3
• TESS Asteroseismology of the known red-giant host stars HD 212771 and HD 203949
• The Kepler-454 System: A Small, Not-rocky Inner Planet, a Jovian World, and a Distant Companion
• Characterization of Kepler-91b and the Investigation of a Potential Trojan Companion Using EXONEST
• A planetary system and a highly eccentric brown dwarf around the giant stars HIP67851 and HIP97233
• Precise Radial Velocity Measurements for Kepler Giants Hosting Planetary Candidates: Kepler-91 and KOI-1894
• Quantifying the Observational Effort Required for the Radial Velocity Characterization of TESS Planets
• Rocky Planet Formation: Quick and Neat
• Ondr}ejov echelle spectrograph, ground based support facility for exoplanet missions
• Do planets remember how they formed?
• TESS Asteroseismic Analysis of the Known Exoplanet Host Star HD 222076
• Kepler's Dark Worlds: a Low Albedo for an Ensemble of Neptunian and Terran Exoplanets
• Transit Clairvoyance: Enhancing TESS follow-up using artificial neural networks
• Variability induced motion in Kepler data
• Synergies between Asteroseismology and Exoplanetary Science
• EXONEST: The Bayesian Exoplanetary Explorer
• Not Gone with the Wind: Planet Occurrence is Independent of Stellar Galactocentric Velocity
• K2-HERMES II. Planet-candidate properties from K2 Campaigns 1-13
• Validation of HD 183579b using archival radial velocities: a warm-neptune orbiting a bright solar analog
• Analysis of the exoplanet containing system Kepler 91
• TESS Asteroseismic Analysis of HD 76920: The Giant Star Hosting An Extremely Eccentric Exoplanet
• Stellar activity and transits
• Using asteroseismology to characterise exoplanet host stars