Gemini-GRACES high-quality spectra of Kepler evolved stars with transiting planets I. Detailed characterization of multi-planet systems Kepler-278 and Kepler-391

Abstract

(abridged) Kepler-278 and Kepler-391 are two of the three evolved stars known to date on the RGB to host multiple short-period transiting planets. Moreover, these planets are among the smallest discovered around RGB stars. Here we present a detailed stellar and planetary characterization of these remarkable systems. Based on high-quality spectra from Gemini-GRACES for Kepler-278 and Kepler-391, we obtained refined stellar parameters and precise chemical abundances for 25 elements. Also, combining our new stellar parameters with a photodynamical analysis of the Kepler light curves, we determined accurate planetary properties of both systems. The precise spectroscopic parameters of Kepler-278 and Kepler-391, along with their high ${}^{12}\mathrm{C}{/}^{13}\mathrm{C}$ ratios, show that both stars are just starting their ascent on the RGB. The planets Kepler-278b, Kepler-278c, and Kepler-391c are warm sub-Neptunes, whilst Kepler-391b is a hot sub-Neptune that falls in the hot super-Earth desert and, therefore, it might be undergoing photoevaporation of its outer envelope. The high-precision obtained in the transit times allowed us not only to confirm Kepler-278c's TTV signal, but also to find evidence of a previously undetected TTV signal for the inner planet Kepler-278b. From the presence of gravitational interaction between these bodies we constrain, for the first time, the mass of Kepler-278b ($M_{\mathrm{p}}$ = 56 $\begin{array}{c}+37\\ -13\end{array}$ $M_{\oplus }$) and Kepler-278c ($M_{\mathrm{p}}$ = 35 $\begin{array}{c}+9.9\\ -21\end{array}$ $M_{\oplus }$). Finally, our photodynamical analysis also shows that the orbits of both planets around Kepler-278 are highly eccentric ($e\sim$ 0.7) and, surprisingly, coplanar. Further observations of this system are needed to confirm the eccentricity values presented here.

arXiv commentAccepted for publication in A&A. 33 pages, 22 figures, 4 tables -v2: Some language editing included and typos corrected

References in corpus (177)

• emcee: The MCMC Hammer
• The chemical composition of the Sun
• Gaia Data Release 2. Summary of the contents and survey properties
• The Wide-field Infrared Survey Explorer (WISE): Mission Description and Initial On-orbit Performance
• PARSEC: stellar tracks and isochrones with the PAdova and TRieste Stellar Evolution Code
• MESA Isochrones and Stellar Tracks (MIST). I: Solar-Scaled Models
• A grid of MARCS model atmospheres for late-type stars I. Methods and general properties
• Evolutionary tracks and isochrones for low- and intermediate-mass stars: from 0.15 to 7 M_sun, and from Z=0.0004 to 0.03
• Analytic Lightcurves for Planetary Transit Searches
• The Dartmouth Stellar Evolution Database
• Evolution of asymptotic giant branch stars II. Optical to far-infrared isochrones with improved TP-AGB models
• A large stellar evolution database for population synthesis studies. I. Scaled solar models and isochrones
• Accurate masses and radii of normal stars: modern results and applications
• REBOUND: An open-source multi-purpose N-body code for collisional dynamics
• 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
• Models of Stars, Brown Dwarfs and Exoplanets
• Efficient, uninformative sampling of limb darkening coefficients for two-parameter laws
• Elemental Abundance Survey of The Galactic Thick Disk
• The NASA Exoplanet Archive: Data and Tools for Exoplanet Research
• Kepler Input Catalog: Photometric Calibration and Stellar Classification
• The evaporation valley in the Kepler planets
• Gaia Data Release 2: using Gaia parallaxes
• An absolutely calibrated effective temperature scale from the InfraRed Flux Method
• Giant Planet Occurrence in the Stellar Mass-Metallicity Plane
• Probabilistic Forecasting of the Masses and Radii of Other Worlds
• VOSA: Virtual Observatory SED Analyzer. An application to the Collinder 69 open cluster
• The effective temperature scale of FGK stars. II. Teff : color : [Fe/H] calibrations
• The California Kepler Survey VII. Precise Planet Radii Leveraging Gaia DR2 Reveal the Stellar Mass Dependence of the Planet Radius Gap
• Validation of Kepler's Multiple Planet Candidates. III: Light Curve Analysis & Announcement of Hundreds of New Multi-planet Systems
• Chromospheric Activity and Jitter Measurements for 2630 Stars on the California Planet Search
• Determining stellar atmospheric parameters and chemical abundances of FGK stars with iSpec
• Basic physical parameters of a selected sample of evolved stars
• Origins of Eccentric Extrasolar Planets: Testing the Planet-Planet Scattering Model
• Revised Stellar Properties of Kepler Targets for the Quarter 1-16 Transit Detection Run
• WHFast: A fast and unbiased implementation of a symplectic Wisdom-Holman integrator for long term gravitational simulations
• The peculiar solar composition and its possible relation to planet formation
• Accurate, Empirical Radii and Masses of Planets and their Host Stars with Gaia Parallaxes
• False positive probabilties for all Kepler Objects of Interest: 1284 newly validated planets and 428 likely false positives
• Mass-Radius Relation for Rocky Planets based on PREM
• The California-Kepler Survey. IV. Metal-rich Stars Host a Greater Diversity of Planets
• NLTE line formation of Fe in late-type stars II: 1D spectroscopic stellar parameters
• Three regimes of extrasolar planets inferred from host star metallicities
• Fundamental Properties of Kepler Planet-Candidate Host Stars using Asteroseismology
• Evidence for a systematic offset of -80 micro-arcseconds in the Gaia DR2 parallaxes
• Improved spectroscopic parameters for transiting planet hosts
• Departures from LTE for neutral Li in late-type stars
• Improving Stellar and Planetary Parameters of Transiting Planet Systems: The Case of TrES-2
• The California-Kepler Survey. I. High Resolution Spectroscopy of 1305 Stars Hosting Kepler Transiting Planets
• A new list of thorium and argon spectral lines in the visible
• Binning is sinning: morphological light-curve distortions due to finite integration time
• The Orbital Evolution of Gas Giant Planets around Giant Stars
• Eccentricity from transit photometry: small planets in Kepler multi-planet systems have low eccentricities
• A Revised Exoplanet Yield from the Transiting Exoplanet Survey Satellite (TESS)
• Revised Stellar Properties of Kepler Targets for the Q1-17 (DR25) Transit Detection Run
• A Revised Effective Temperature Scale for the Kepler Input Catalog
• ASTEC -- the Aarhus STellar Evolution Code
• Asteroseismology and Gaia: Testing Scaling Relations Using 2200 Kepler Stars with TGAS Parallaxes
• High-precision abundances of elements in solar twin stars: Trends with stellar age and elemental condensation temperature
• Retired A Stars and Their Companions: Exoplanets Orbiting Three Intermediate-Mass Subgiants
• The accretion of planets and brown dwarfs by giant stars -- II. solar mass stars on the red giant branch
• Hot super-Earths stripped by their host stars
• The Impact of Stellar Multiplicity on Planetary Systems, I.: The Ruinous Influence of Close Binary Companions
• The Kepler Follow-Up Observation Program. I. A Catalog of Companions to Kepler Stars from High-Resolution Imaging
• Lack of Inflated Radii for Kepler Giant Planet Candidates Receiving Modest Stellar Irradiation
• The orbital eccentricity of small planet systems
• Precise Radial Velocities of Giant Stars VII. Occurrence Rate of Giant Extrasolar Planets as a Function of Mass and Metallicity
• KOI-126: A Triply-Eclipsing Hierarchical Triple with Two Low-Mass Stars
• Precise radial velocities of giant stars. III. Spectroscopic stellar parameters
• Asteroseismology of 16000 Kepler Red Giants: Global Oscillation Parameters, Masses, and Radii
• Validation of Kepler's Multiple Planet Candidates. II: Refined Statistical Framework and Descriptions of Systems of Special Interest
• Planets around evolved intermediate-mass stars. I. Two substellar companions in the open clusters NGC 2423 and NGC 4349
• Tidal Evolution of Close-in Planets
• Stellar Rotation Periods of the Kepler Objects of Interest: A Dearth of Close-in Planets around Fast Rotators
• Atmospheres of low-mass planets: the "boil-off"
• YREC: The Yale Rotating Stellar Evolution Code
• ARES v2 - new features and improved performance
• Accurate parameters of 93 solar-type Kepler targets
• Mixed modes in red giants: a window on stellar evolution
• Hot Jupiters and Cool Stars
• Fundamental Parameters and Chemical Composition of Arcturus
• A generalized bayesian inference method for constraining the interiors of super Earths and sub-Neptunes
• Stellar Parameters and Elemental Abundances of Late-G Giants
• Galactic archaeology: mapping and dating stellar populations with asteroseismology of red-giant stars
• Chemical abundances of 1111 FGK stars from the HARPS GTO planet search program II: Cu, Zn, Sr, Y, Zr, Ba, Ce, Nd and Eu
• Oxygen Abundances in Nearby Stars. Clues to the formation and evolution of the Galactic disk
• Hot Jupiters from Coplanar High-eccentricity Migration
• Transit Timing Observations from Kepler. IX. Catalog of the Full Long-Cadence Data Set
• The Solar Twin Planet Search. I. Fundamental parameters of the stellar sample
• Transit Timing Observations from Kepler: VII. Confirmation of 27 planets in 13 multiplanet systems via Transit Timing Variations and orbital stability
• Planetary Candidates Observed by Kepler V: Planet Sample from Q1-Q12 (36 Months)
• The remarkable solar twin HIP 56948: a prime target in the quest for other Earths
• The California-Kepler Survey. II. Precise Physical Properties of 2025 Kepler Planets and Their Host Stars
• Chemical abundances of 451 stars from the HARPS GTO planet search program: Thin disc, thick disc, and planets
• Elemental abundance differences in the 16 Cygni binary system: a signature of gas giant planet formation?
• Improved stellar parameters of CoRoT-7
• An in-depth study of grid-based asteroseismic analysis
• Photometric Amplitude Distribution of Stellar Rotation of Kepler KOIs-Indication for Spin-Orbit Alignment of Cool Stars and High Obliquity for Hot Stars
• Stellar parameters and chemical abundances of 223 evolved stars with and without planets
• The Mount Wilson Observatory S-index of the Sun
• Planet Engulfment by ~1.5-3 Solar-Mass Red Giants
• The asteroseismic potential of TESS: exoplanet-host stars
• Origin of lithium enrichment in K giants
• Activity indicators and stellar parameters of the Kepler targets. An application of the ROTFIT pipeline to LAMOST-Kepler stellar spectra
• An Improved Method for Estimating the Masses of Stars with Transiting Planets
• Searching for the signatures of terrestrial planets in F-, G-type main-sequence stars
• Transit timing variations in WASP-10b induced by stellar activity?
• Observable Signatures of Planet Accretion in Red Giant Stars I: Rapid Rotation and Light Element Replenishment
• Retired A Stars Revisited: An Updated Giant Planet Occurrence Rate as a Function of Stellar Metallicity and Mass
• Stellar Chemical Abundances: In Pursuit of the Highest Achievable Precision
• A Spectroscopic Analysis of the California-Kepler Survey Sample: I. Stellar Parameters, Planetary Radii and a Slope in the Radius Gap
• New and updated stellar parameters for 90 transit hosts. The effect of the surface gravity
• Planetary Companions around Three Intermediate-Mass G and K Giants: 18 Del, xi Aql, and HD 81688
• The Solar Twin Planet Search III. The [Y/Mg] clock: estimating stellar ages of solar-type stars
• Planetary Systems in Binaries. I. Dynamical Classification
• Correcting the spectroscopic surface gravity using transits and asteroseismology. No significant effect on temperatures or metallicities with ARES+MOOG in LTE
• On Lithium-Rich Red Giants. I. Engulfment of Sub-Stellar Companions
• Assembling the Building Blocks of Giant Planets around Intermediate Mass Stars
• Re-inflated Warm Jupiters Around Red Giants
• A Hot Saturn Orbiting An Oscillating Late Subgiant Discovered by TESS
• Correlation between lithium abundances and ages of solar twin stars
• The Hamburg/ESO R-process Enhanced Star survey (HERES). V. Detailed abundance analysis of the r-process enhanced star HE 2327-5642
• A possible signature of terrestrial planet formation in the chemical composition of solar analogs
• Kepler-432: a red giant interacting with one of its two long period giant planets
• High-precision abundances of Sc, Mn, Cu, and Ba in solar twins. Trends of element ratios with stellar age
• The metallicity signature of evolved stars with planets
• Atmospheric parameters of 82 red giants in the Kepler field
• Seeing double with K2: Testing re-inflation with two remarkably similar planets around red giant branch stars
• Detection of Potential Transit Signals in 17 Quarters of Kepler Data: Results of the Final Kepler Mission Transiting Planet Search (DR25)
• On the Semimajor Axis Distribution of Extrasolar Gas Giant Planets: Why Hot Jupiters Are Rare Around High-Mass Stars
• Gaia FGK Benchmark stars: Opening the black box of stellar element abundance determination
• On the metallicity dependance of the [Y/Mg] - age relation for solar type stars
• Bayesian analysis of interiors of HD 219134b, Kepler-10b, Kepler-93b, CoRoT-7b, 55 Cnc e, and HD 97658b using stellar abundance proxies
• A Comparison of Stellar Elemental Abundance Techniques and Measurements
• Are Stars with Planets Polluted?
• Metallicities of Planet Hosting Stars: A Sample of Giants and Subgiants
• K2-97b: A (Re-?)Inflated Planet Orbiting a Red Giant Star
• A Planet in a 0.6-AU Orbit Around the K0 Giant HD 102272
• CKS VIII: Eccentricities of Kepler Planets and Tentative Evidence of a High Metallicity Preference for Small Eccentric Planets
• Planetary companions around the K giant stars 11 UMi and HD 32518
• Spectral Properties of Cool Stars: Extended Abundance Analysis of Kepler Objects of Interest
• The Separation/Period Gap in the Distribution of Extrasolar Planets around Stars with Masses M >= 1.2 Msolar
• BD+48 740 - Li overabundant giant star with a planet. A case of recent engulfment?
• Asteroseismic surface gravity for evolved stars
• Signatures of rocky planet engulfment in HAT-P-4. Implications for chemical tagging studies
• Evolved stars and the origin of abundance trends in planet hosts
• A Granulation "Flicker"-based Measure of Stellar Surface Gravity
• Lithium Abundances in a Sample of Planet Hosting Dwarfs
• The Solar Twin Planet Search. V. Close-in, low-mass planet candidates and evidence of planet accretion in the solar twin HIP 68468
• The Penn State - Torun Centre for Astronomy Planet Search stars. II. Lithium abundance analysis of the Red Giant Clump sample
• Super-Nyquist asteroseismology of solar-like oscillators with Kepler and K2 - expanding the asteroseismic cohort at the base of the red-giant branch
• On Infrared Excesses Associated With Li-Rich K Giants
• The K2-ESPRINT Project V: a short-period giant planet orbiting a subgiant star
• Do close-in giant planets orbiting evolved stars prefer eccentric orbits?
• Atmospheric parameters and chemical properties of red giants in the CoRoT asteroseismology fields
• Substellar Companions to Evolved Intermediate-Mass Stars: HD 145457 and HD 180314
• Radial velocity confirmation of Kepler-91 b. Additional evidence of its planetary nature using the Calar Alto/CAFE instrument
• Assessing the accuracy of the gravity determination in late-type stars with solar-like pulsators
• Homogeneous photospheric parameters and C abundances in G and K nearby stars with and without planets
• An Effective temperature calibration for solar type stars using equivalent width ratios - A fast and easy spectroscopic temperature estimation
• Identifying Young $Kepler$ Planet Host Stars from Keck-HIRES Spectra of Lithium
• The [Y/Mg] clock works for evolved solar metallicity stars
• Chemical abundances and kinematics of 257 G-, K-type field giants. Setting a base for further analysis of giant-planet properties orbiting evolved stars
• Absolute densities in exoplanetary systems: photodynamical modelling of Kepler-138
• Absolute masses and radii determination in multiplanetary systems without stellar models
• HD 80606: Searching the chemical signature of planet formation
• The Curious Case of KOI 4: Confirming Kepler's First Exoplanet
• Chemical compositions of thin-disk, high-metallicity red horizontal-branch field stars
• TAPAS - Tracking Advanced Planetary Systems with HARPS-N. II. Super Li-rich giant HD 107028
• KIC 9821622: An interesting lithium-rich giant in the Kepler field
• Sulfur and zinc abundances of red giant stars
• SOPHIE velocimetry of Kepler transit candidates XVIII. Radial velocity confirmation, absolute masses and radii, and origin of the Kepler-419 multiplanetary system
• Subgiants as probes of galactic chemical evolution
• Atmospheric parameters of red giants in the Kepler field
• Distribution of refractory and volatile elements in CoRoT exoplanet host stars
• Using non-solar-scaled opacities to derive stellar parameters. Toward high-precision parameters and abundances
• The Homogenous Study of Transiting Systems (HoSTS). II. The influence of the line list on stellar parameters

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