K2-140b and K2-180b - Characterization of a hot Jupiter and a mini-Neptune from the K2 mission

Abstract

We report the independent discovery and characterization of two K2 planets: K2-180b, a mini-Neptune-size planet in an 8.9-day orbit transiting a V = 12.6 mag, metal-poor ([Fe/H] =$-0.65\pm 0.10$) K2V star in K2 campaign 5; K2-140b, a transiting hot Jupiter in a 6.6-day orbit around a V = 12.6 mag G6V ([Fe/H] = $+0.10\pm 0.10$) star in K2 campaign 10. Our results are based on K2 time-series photometry combined with high-spatial resolution imaging and high-precision radial velocity measurements. We present the first mass measurement of K2-180b. K2-180b has a mass of $M_{\mathrm{p}}=11.3\pm 1.9$ $M_{\oplus }$ and a radius of $R_{\mathrm{p}}=2.2\pm 0.1$ $R_{\oplus }$ , yielding a mean density of ${\rho }_{\mathrm{p}}=5.6\pm 1.9gc{m}^{-3}$, suggesting a rock composition. Given its radius, K2-180b is above the region of the so-called `planetary radius gap'. K2-180b is in addition not only one of the densest mini-Neptune-size planets, but also one of the few mini-Neptune-size planets known to transit a metal-poor star. We also constrain the planetary and orbital parameters of K2-140b and show that, given the currently available Doppler measurements, the eccentricity is consistent with zero, contrary to the results of a previous study.

arXiv commentaccepted in MNRAS

References in corpus (84)

• Gaia Data Release 2. Summary of the contents and survey properties
• The Gaia mission
• PARSEC: stellar tracks and isochrones with the PAdova and TRieste Stellar Evolution Code
• The Transiting Exoplanet Survey Satellite
• The Eleventh and Twelfth Data Releases of the Sloan Digital Sky Survey: Final Data from SDSS-III
• Intrinsic Colors, Temperatures, and Bolometric Corrections of Pre-Main Sequence Stars
• Analytic Lightcurves for Planetary Transit Searches
• The K2 Mission: Characterization and Early results
• The California-Kepler Survey. III. A Gap in the Radius Distribution of Small Planets
• 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
• The PLATO 2.0 Mission
• Planetary Candidates Observed by Kepler, III: Analysis of the First 16 Months of Data
• Planetary Radii across Five Orders of Magnitude in Mass and Stellar Insolation: Application to Transits
• A box-fitting algorithm in the search for periodic transits
• The Occurrence and Architecture of Exoplanetary Systems
• Kepler planets: a tale of evaporation
• The evaporation valley in the Kepler planets
• Gaia Data Release 2: using Gaia parallaxes
• Defining and cataloging exoplanets: The exoplanet.eu database
• A Technique for Extracting Highly Precise Photometry for the Two-Wheeled Kepler Mission
• Transiting exoplanets from the CoRoT space mission VIII. CoRoT-7b: the first Super-Earth with measured radius
• Homogeneous studies of transiting extrasolar planets. IV. Thirty systems with space-based light curves
• An asteroseismic view of the radius valley: stripped cores, not born rocky
• The Role of Core Mass in Controlling Evaporation: the Kepler Radius Distribution and the Kepler-36 Density Dichotomy
• Core-powered mass loss and the radius distribution of small exoplanets
• Basic physical parameters of a selected sample of evolved stars
• An Empirical Relation between Sodium Absorption and Dust Extinction
• On the use of empirical bolometric corrections for stars
• Mass-Radius Relation for Rocky Planets based on PREM
• Spectroscopy Made Easy: Evolution
• Ages and fundamental properties of Kepler exoplanet host stars from asteroseismology
• HAT-P-16b: A 4 Mj Planet Transiting A Bright Star On An Eccentric Orbit
• Terrestrial Planet Occurrence Rates for the Kepler GK Dwarf Sample
• The California-Kepler Survey. IV. Metal-rich Stars Host a Greater Diversity of Planets
• Planetary population synthesis coupled with atmospheric escape: a statistical view of evaporation
• Three regimes of extrasolar planets inferred from host star metallicities
• Parameter Estimation from Time-Series Data with Correlated Errors: A Wavelet-Based Method and its Application to Transit Light Curves
• Detailed Models of super-Earths: How well can we infer bulk properties?
• Precision Stellar Characterization of FGKM Stars using an Empirical Spectral Library
• Compositional imprints in density-distance-time: a rocky composition for close-in low-mass exoplanets from the location of the valley of evaporation
• An Efficient Automated Validation Procedure for Exoplanet Transit Candidates
• Accurate fundamental parameters for 23 bright solar-type stars
• An Earth-sized planet with an Earth-like density
• 197 Candidates and 104 Validated Planets in K2's First Five Fields
• Efficient fitting of multiplanet Keplerian models to radial velocity and astrometry data
• Oxygen Abundances in Nearby Stars. Clues to the formation and evolution of the Galactic disk
• Revealing A Universal Planet-Metallicity Correlation For Planets of Different Sizes Around Solar-Type Stars
• 275 Candidates and 149 Validated Planets Orbiting Bright Stars in K2 Campaigns 0-10
• The K2-ESPRINT Project. I. Discovery of the Disintegrating Rocky Planet K2-22b with a Cometary Head and Leading Tail
• Estimating distances from parallaxes. II. Performance of Bayesian distance estimators on a Gaia-like catalogue
• The effect of stellar limb darkening values on the accuracy of the planet radii derived from photometric transit observations
• An Improved Method for Estimating the Masses of Stars with Transiting Planets
• Accounting for velocity jitter in planet search surveys
• A Definition for Giant Planets Based on the Mass-Density Relationship
• Transiting exoplanet candidates from K2 Campaigns 5 and 6
• LAMOST telescope reveals that Neptunian cousins of hot Jupiters are mostly single offspring of stars that are rich in heavy elements
• A Super-Solar Metallicity For Stars With Hot Rocky Exoplanets
• Exoplanets around Low-mass Stars Unveiled by K2
• 44 Validated Planets from K2 Campaign 10
• Metallicity-Dependent Signatures in the Kepler Planets
• Jupiter Analogues Orbit Stars with an Average Metallicity Close to that of the Sun
• The frequency of giant planets around metal-poor stars
• Transiting exoplanets from the CoRoT space mission XXVIII. CoRoT-33b, an object in the brown dwarf desert with 2:3 commensurability with its host star
• Optimizing the search for transiting planets in long time series
• Three Small Super-Earths Transiting the nearby star GJ 9827
• A study of the performance of the transit detection tool DST in space-based surveys. Application of the CoRoT pipeline to Kepler data
• K2-137 b: an Earth-sized planet in a 4.3-hour orbit around an M-dwarf
• Kepler-77b: a very low albedo, Saturn-mass transiting planet around a metal-rich solar-like star
• Planet Candidates from K2 Campaigns 5-8 and Follow-Up Optical Spectroscopy
• Transiting exoplanets from the CoRoT space mission XVII. The hot Jupiter CoRoT-17b: a very old planet
• Tidal interactions of close-in extrasolar planets: the OGLE cases
• An upper boundary in the mass-metallicity plane of exo-Neptunes
• The K2-ESPRINT Project III: A Close-in Super-Earth around a Metal-rich Mid-M Dwarf
• The stellar obliquity, planet mass, and very low albedo of Qatar-2 from K2 Photometry
• Spherically symmetric model stellar atmospheres and limb darkening II: limb-darkening laws, gravity-darkening coefficients and angular diameter corrections for FGK dwarf stars
• The HARPS search for southern extra-solar planets. XXXIX. HD175607 b, the most metal-poor G dwarf with an orbiting sub-Neptune
• K2-110 b - a massive mini-Neptune exoplanet
• Robust Transiting Exoplanet Radii in the Presence of Starspots from Ingress and Egress Durations
• Two Hot Jupiters from K2 Campaign 4
• K2-31b, a grazing transiting hot Jupiter on an 1.26-day orbit around a bright G7V star
• EPIC 228735255b - An eccentric 6.57 day transiting hot Jupiter in Virgo
• The HARPS search for southern extra-solar planets XL. Searching for Neptunes around metal-poor stars
• Wavelet-based filter methods to detect small transiting planets in stellar light curves

Cited by in corpus (17)

• Juliet: a versatile modelling tool for transiting and non-transiting exoplanetary systems
• Revisited Mass-Radius relations for exoplanets below 120 Earth masses
• Stellar obliquities in exoplanetary systems
• ExoClock Project III: 450 new exoplanet ephemerides from ground and space observations
• The BAyesian STellar Algorithm (BASTA): a fitting tool for stellar studies, asteroseismology, exoplanets, and Galactic archaeology
• A pair of Sub-Neptunes transiting the bright K-dwarf TOI-1064 characterised with CHEOPS
• TOI-503: The first known brown dwarf-Am star binary from the TESS mission
• Shallower radius valley around low-mass hosts: Evidence for icy planets, collisions or high-energy radiation scatter
• Stellar Obliquities in Long-period Exoplanet Systems (SOLES) I: The Spin-Orbit Alignment of K2-140 b
• 37 New Validated Planets in Overlapping K2 Campaigns
• The K2-OjOS Project: New and revisited planets and candidates in K2 campaigns 5, 16, & 18
• Exoplanet atmosphere evolution: emulation with neural networks
• The K2 & TESS Synergy II: Revisiting 26 systems in the TESS Primary Mission
• Lack of close-in, massive planets of main-sequence A-type stars from Kepler
• Greening of the Brown Dwarf Desert. EPIC 212036875 b -- a 51 M${}_{\mathrm{J}}$ object in a 5 day orbit around an F7 V star
• The multi-planet system TOI-421 -- A warm Neptune and a super puffy mini-Neptune transiting a G9 V star in a visual binary
• Characterisation of TOI-406 as showcase of the THIRSTEE program: A 2-planet system straddling the M-dwarf density gap