Global Analysis of KOI-977: Spectroscopy, Asteroseismology, and Phase-curve Analysis

Abstract

We present a global analysis of KOI-977, one of the planet host candidates detected by {\it Kepler}. Kepler Input Catalog (KIC) reports that KOI-977 is a red giant, for which few close-in planets have been discovered. Our global analysis involves spectroscopic and asteroseismic determinations of stellar parameters (e.g., mass and radius) and radial velocity (RV) measurements. Our analyses reveal that KOI-977 is indeed a red giant in the red clump, but its estimated radius ($\gtrsim 20R_{\odot }=0.093$ AU) is much larger than KOI-977.01's orbital distance ($\sim 0.027$ AU) estimated from its period ($P_{\mathrm{orb}}\sim 1.35$ days) and host star's mass. RV measurements show a small variation, which also contradicts the amplitude of ellipsoidal variations seen in the light-curve folded with KOI-977.01's period. Therefore, we conclude that KOI-977.01 is a false positive, meaning that the red giant, for which we measured the radius and RVs, is different from the object that produces the transit-like signal (i.e., an eclipsing binary). On the basis of this assumption, we also perform a light-curve analysis including the modeling of transits/eclipses and phase-curve variations, adopting various values for the dilution factor $D$, which is defined as the flux ratio between the red giant and eclipsing binary. Fitting the whole folded light-curve as well as individual transits in the short cadence data simultaneously, we find that the estimated mass and radius ratios of the eclipsing binary are consistent with those of a solar-type star and a late-type star (e.g., an M dwarf) for $D\gtrsim 20$.

arXiv comment12 pages, 9 figures, accepted for publication in ApJ

References in corpus (43)

• The chemical composition of the Sun
• The Dartmouth Stellar Evolution Database
• The false positive rate of Kepler and the occurrence of planets
• Planetary Candidates Observed by Kepler, III: Analysis of the First 16 Months of Data
• Kepler Presearch Data Conditioning II - A Bayesian Approach to Systematic Error Correction
• Towards Better Age Estimates for Stellar Populations: The Y^2 Isochrones for Solar Mixture
• A map of the day-night contrast of the extrasolar planet HD 189733b
• Kepler Presearch Data Conditioning I - Architecture and Algorithms for Error Correction in Kepler Light Curves
• Kepler-16: A Transiting Circumbinary Planet
• A Closely-Packed System of Low-Mass, Low-Density Planets Transiting Kepler-11
• The Occurrence Rate of Small Planets around Small Stars
• Gravity modes as a way to distinguish between hydrogen- and helium-burning red giant stars
• ADIPLS -- the Aarhus adiabatic oscillation package
• Testing Scaling Relations for Solar-Like Oscillations from the Main Sequence to Red Giants using Kepler Data
• Stellar Spin-Orbit Misalignment in a Multiplanet System
• Almost All of Kepler's Multiple Planet Candidates are Planets
• An Earth-sized Planet in the Habitable Zone of a Cool Star
• Inference of Inhomogeneous Clouds in an Exoplanet Atmosphere
• Preparation of Kepler lightcurves for asteroseismic analyses
• Determining global parameters of the oscillations of solar-like stars
• Possible Disintegrating Short-Period Super-Mercury Orbiting KIC 12557548
• Transit Timing Observations from Kepler: VII. Confirmation of 27 planets in 13 multiplanet systems via Transit Timing Variations and orbital stability
• Photometric detection of non-transiting short-period low-mass companions through the beaming, ellipsoidal and reflection effects in Kepler and CoRoT lightcurves
• Characterizing the Cool Kepler Objects of Interest. New Effective Temperatures, Metallicities, Masses and Radii of Low-Mass Kepler Planet-Candidate Host Stars
• Planet Engulfment by ~1.5-3 Solar-Mass Red Giants
• Kepler-91b: a planet at the end of its life. Planet and giant host star properties via light-curve variations
• Bayesian peak-bagging of solar-like oscillators using MCMC: A comprehensive guide
• Evidence for the Tidal Destruction of Hot Jupiters by Subgiant Stars
• Planet-Planet Eclipse and the Rossiter-McLaughlin Effect of a Multiple Transiting System: Joint Analysis of the Subaru Spectroscopy and the Kepler Photometry
• Planetary Companions around Three Intermediate-Mass G and K Giants: 18 Del, xi Aql, and HD 81688
• Detection Of KOI-13.01 Using The Photometric Orbit
• Measurements of Stellar Inclinations for Kepler Planet Candidates
• A hot Jupiter orbiting the 1.7 Msun Subgiant HD102956
• The properties of planets around giant stars
• A fresh look at the seismic spectrum of HD49933: analysis of 180 days of CoRoT photometry
• Predicting Photometric and Spectroscopic Signatures of Rings around Transiting Extrasolar Planets
• The art of fitting p-mode spectra: Part I. Maximum Likelihood Estimation
• Measurements of Stellar Inclinations for Kepler Planet Candidates II: Candidate Spin-Orbit Misalignments in Single and Multiple-Transiting Systems
• Inferring mode inertias in evolved solar-like stars
• Characterizing the Cool KOIs. VI. H- and K-band Spectra of Kepler M Dwarf Planet-Candidate Hosts
• Properties of oscillation modes in subgiant stars observed by Kepler
• The EVIL-MC Model for Ellipsoidal Variations of Planet-Hosting Stars and Applications to the HAT-P-7 System
• The image slicer for the Subaru Telescope High Dispersion Spectrograph

Cited by in corpus (12)

• They are Small Worlds After All: Revised Properties of Kepler M Dwarf Stars and their Planets
• Exoplanets around Low-mass Stars Unveiled by K2
• Precision radial velocity measurements by the forward-modeling technique in the near-infrared
• Discovery of three self-lensing binaries from Kepler
• The K2-ESPRINT Project III: A Close-in Super-Earth around a Metal-rich Mid-M Dwarf
• Precise Radial Velocity Measurements for Kepler Giants Hosting Planetary Candidates: Kepler-91 and KOI-1894
• The K2-ESPRINT Project IV: A Hot Jupiter in a Prograde Orbit with a Possible Stellar Companion
• K2-155: A Bright Metal-Poor M Dwarf with Three Transiting Super-Earths
• Characterization of the K2-19 Multiple-Transiting Planetary System via High-Dispersion Spectroscopy, AO Imaging, and Transit Timing Variations
• Automated approach to measure stellar inclinations: validation through large-scale measurements on the red giant branch
• An Earth-sized Planet around an M5 Dwarf Star at 22 pc
• Two Bright M Dwarfs Hosting Ultra-Short-Period Super-Earths with Earth-like Compositions