The K2-ESPRINT Project VI: K2-105 b, a Hot-Neptune around a Metal-rich G-dwarf

Abstract

We report on the confirmation that the candidate transits observed for the star EPIC 211525389 are due to a short-period Neptune-sized planet. The host star, located in K2 campaign field 5, is a metal-rich ([Fe/H] = 0.26$\pm$0.05) G-dwarf (T_eff = 5430$\pm$70 K and log g = 4.48$\pm$0.09), based on observations with the High Dispersion Spectrograph (HDS) on the Subaru 8.2m telescope. High-spatial resolution AO imaging with HiCIAO on the Subaru telescope excludes faint companions near the host star, and the false positive probability of this target is found to be <$10^{-6}$ using the open source vespa code. A joint analysis of transit light curves from K2 and additional ground-based multi-color transit photometry with MuSCAT on the Okayama 1.88m telescope gives the orbital period of P = 8.266902$\pm$0.000070 days and consistent transit depths of $R_p/R_{\star }\sim 0.035$ or $(R_p/R_{\star }{)}^2\sim 0.0012$. The transit depth corresponds to a planetary radius of $R_p=3.59_{-0.39}^{+0.44}{R}_{\oplus }$, indicating that EPIC 211525389 b is a short-period Neptune-sized planet. Radial velocities of the host star, obtained with the Subaru HDS, lead to a 3σ upper limit of 90 $M_{\oplus }(0.00027M_{\odot })$ on the mass of EPIC 211525389 b, confirming its planetary nature. We expect this planet, newly named K2-105 b, to be the subject of future studies to characterize its mass, atmosphere, spin-orbit (mis)alignment, as well as investigate the possibility of additional planets in the system.

arXiv comment11 pages, 9 figures, 4 tables, PASJ accepted

References in corpus (59)

• The Gaia mission
• Analytic Lightcurves for Planetary Transit Searches
• The Dartmouth Stellar Evolution Database
• The K2 Mission: Characterization and Early results
• Accurate masses and radii of normal stars: modern results and applications
• Astrophysics Source Code Library
• Planet Occurrence within 0.25 AU of Solar-type Stars from Kepler
• A box-fitting algorithm in the search for periodic transits
• Achieving better than 1 minute accuracy in the Heliocentric and Barycentric Julian Dates
• Towards Better Age Estimates for Stellar Populations: The Y^2 Isochrones for Solar Mixture
• Prevalence of Earth-size planets orbiting Sun-like stars
• Kepler planets: a tale of evaporation
• Overview of the Kepler Science Processing Pipeline
• Gaia Data Release 1: Astrometry - one billion positions, two million proper motions and parallaxes
• The effect of red noise on planetary transit detection
• Quantifying the Uncertainty in the Orbits of Extrasolar Planets
• Dearth of short-period Neptunian exoplanets - a desert in period-mass and period-radius planes
• The Transit Light Curve Project. IX. Evidence for a Smaller Radius of the Exoplanet XO-3b
• The K2 Ecliptic Plane Input Catalog (EPIC) and Stellar Classifications of 138,600 Targets in Campaigns 1-8
• Make Super-Earths, Not Jupiters: Accreting Nebular Gas onto Solid Cores at 0.1 AU and Beyond
• An Efficient Automated Validation Procedure for Exoplanet Transit Candidates
• A Detailed Model Grid for Solid Planets from 0.1 through 100 Earth Masses
• Accurate fundamental parameters for 23 bright solar-type stars
• In-situ Accretion of Hydrogen-Rich Atmospheres on Short-Period Super-Earths: Implications for the Kepler-11 Planets
• 197 Candidates and 104 Validated Planets in K2's First Five Fields
• Hydrodynamics of Embedded Planets' First Atmospheres. II. A Rapid Recycling of Atmospheric Gas
• Emerging Trends in a Period-Radius Distribution of Close-in Planets
• A nearby M star with three transiting super-Earths discovered by K2
• Zodiacal Exoplanets In Time (ZEIT) I: A Neptune-sized planet orbiting an M4.5 dwarf in the Hyades Star Cluster
• The K2-ESPRINT Project. I. Discovery of the Disintegrating Rocky Planet K2-22b with a Cometary Head and Leading Tail
• Effect of stellar spots on high-precision transit light-curve
• Measurement of the Rossiter--McLaughlin Effect in the Transiting Exoplanetary System TrES-1
• Properties of analytic transit light curve models
• Measurements of Stellar Inclinations for Kepler Planet Candidates
• On stellar limb darkening and exoplanetary transits
• New planetary and EB candidates from Campaigns 1-6 of the K2 mission
• Transiting exoplanet candidates from K2 Campaigns 5 and 6
• Measurements of Transit Timing Variations for WASP-5b
• Orbital and physical properties of planets and their hosts: new insights on planet formation and evolution
• On the origin of the sub-Jovian desert in the orbital-period--planetary-mass plane
• Predicting Photometric and Spectroscopic Signatures of Rings around Transiting Extrasolar Planets
• MuSCAT: a multicolor simultaneous camera for studying atmospheres of transiting exoplanets
• Measurements of Stellar Inclinations for Kepler Planet Candidates II: Candidate Spin-Orbit Misalignments in Single and Multiple-Transiting Systems
• Accretion and Evolution of ~2.5 Earth-mass Planets with Voluminous H/He Envelopes
• New Techniques for High-Contrast Imaging with ADI: the ACORNS-ADI SEEDS Data Reduction Pipeline
• Optimizing the search for transiting planets in long time series
• Multi-Color Transit Photometry of GJ 1214b through BJHKs-Bands and a Long-Term Monitoring of the Stellar Variability of GJ 1214
• Doppler Monitoring of five K2 Transiting Planetary Systems
• One of the closest exoplanet pairs to the 3:2 Mean Motion Resonance: K2-19b \& c
• The K2-ESPRINT Project V: a short-period giant planet orbiting a subgiant star
• The K2-ESPRINT Project III: A Close-in Super-Earth around a Metal-rich Mid-M Dwarf
• The image slicer for the Subaru Telescope High Dispersion Spectrograph
• A possible correlation between planetary radius and orbital period for small planets
• The K2-ESPRINT Project IV: A Hot Jupiter in a Prograde Orbit with a Possible Stellar Companion
• Demonstrating High-precision, Multiband Transit Photometry with MuSCAT: A Case for HAT-P-14b
• The K2-ESPRINT Project II: Spectroscopic follow-up of three exoplanet systems from Campaign 1 of K2
• Characterization of the K2-19 Multiple-Transiting Planetary System via High-Dispersion Spectroscopy, AO Imaging, and Transit Timing Variations
• K2-30b and K2-34b: two inflated hot-Jupiters around Solar-type stars
• Ground-based Transit Observation of the Habitable-zone Super-Earth K2-3d

Cited by in corpus (8)

• MuSCAT2: four-color Simultaneous Camera for the 1.52-m Telescopio Carlos Sánchez
• DREAM I. Orbital architecture orrery
• K2-141 b: A 5-M${}_{\oplus }$ super-Earth transiting a K7 V star every 6.7 hours
• K2-106, a system containing a metal-rich planet and a planet of lower density
• K2-260 b: a hot Jupiter transiting an F star, and K2-261 b: a warm Saturn around a bright G star
• Connection between planetary He I $\lambda$10830 Å absorption and extreme-ultraviolet emission of planet-host stars
• DREAM: III.A helium survey in exoplanets on the edge of the hot Neptune desert with GIANO-B@TNG
• The Occurrence-weighted Median Planets Discovered by Transit Surveys Orbiting Solar-type Stars and Their Implications for Planet Formation and Evolution