The discovery and mass measurement of a new ultra-short-period planet: EPIC~228732031b

Abstract

We report the discovery of a new ultra-short-period planet and summarize the properties of all such planets for which the mass and radius have been measured. The new planet, EPIC~228732031b, was discovered in {\it K2} Campaign 10. It has a radius of 1.81${}_{-0.12}^{+0.16}{R}_{\oplus }$ and orbits a G dwarf with a period of 8.9 hours. Radial velocities obtained with Magellan/PFS and TNG/HARPS-N show evidence for stellar activity along with orbital motion. We determined the planetary mass using two different methods: (1) the "floating chunk offset" method, based only on changes in velocity observed on the same night, and (2) a Gaussian process regression based on both the radial-velocity and photometric time series. The results are consistent and lead to a mass measurement of $6.5\pm 1.6M_{\oplus }$, and a mean density of $6.0_{-2.7}^{+3.0}$~g~cm${}^{-3}$.

arXiv comment24 pages, 14 figures, accepted to AJ

References in corpus (60)

• emcee: The MCMC Hammer
• MultiNest: an efficient and robust Bayesian inference tool for cosmology and particle physics
• A grid of MARCS model atmospheres for late-type stars I. Methods and general properties
• The Dartmouth Stellar Evolution Database
• The California-Kepler Survey. III. A Gap in the Radius Distribution of Small Planets
• Accurate masses and radii of normal stars: modern results and applications
• batman: BAsic Transit Model cAlculatioN in Python
• Information criteria for astrophysical model selection
• A box-fitting algorithm in the search for periodic transits
• Kepler planets: a tale of evaporation
• Most 1.6 Earth-Radius Planets are not Rocky
• The evaporation valley in the Kepler planets
• EXOFAST: A fast exoplanetary fitting suite in IDL
• Rotation Periods of 34,030 Kepler Main-Sequence Stars: The Full Autocorrelation Sample
• Understanding the Mass-Radius Relation for Sub-Neptunes: Radius as a Proxy for Composition
• A Technique for Extracting Highly Precise Photometry for the Two-Wheeled Kepler Mission
• KEPLER's First Rocky Planet: Kepler-10b
• Planets and Stellar Activity: Hide and Seek in the CoRoT-7 system
• 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
• The NextGen Model Atmosphere grid: II. Spherically symmetric model atmospheres for giant stars with effective temperatures between 3000 and 6800~K
• Mass-Radius Relation for Rocky Planets based on PREM
• Spectroscopy Made Easy: Evolution
• Binning is sinning: morphological light-curve distortions due to finite integration time
• Precision Stellar Characterization of FGKM Stars using an Empirical Spectral Library
• A simple method to estimate radial velocity variations due to stellar activity using photometry
• WASP-47: A Hot Jupiter System with Two Additional Planets Discovered by K2
• Hot super-Earths stripped by their host stars
• A Study of the Shortest-Period Planets Found With Kepler
• Determining stellar macroturbulence using asteroseismic rotational velocities from Kepler
• Accurate fundamental parameters for 23 bright solar-type stars
• The Mass of Kepler-93b and The Composition of Terrestrial Planets
• An Earth-sized planet with an Earth-like density
• The Sun as a planet-host star: Proxies from SDO images for HARPS radial-velocity variations
• A Rocky Composition for an Earth-sized Exoplanet
• The fundamental definition of 'radial velocity'
• Born Dry in the Photo-Evaporation Desert: Kepler's Ultra-Short-Period Planets Formed Water-Poor
• Transits and Occultations of an Earth-Sized Planet in an 8.5-Hour Orbit
• Determining the Mass of Kepler-78b With Nonparametric Gaussian Process Estimation
• Variability in the super-Earth 55 Cnc e
• Improved stellar parameters of CoRoT-7
• On the Mass of CoRoT-7b
• The Mount Wilson Observatory S-index of the Sun
• The Roche limit for close-orbiting planets: Minimum density, composition constraints, and application to the 4.2-hour planet KOI 1843.03
• Magnetospheric Truncation, Tidal Inspiral, and the Creation of Short and Ultra-Short Period Planets
• 55 Cancri: Stellar Astrophysical Parameters, a Planet in the Habitable Zone, and Implications for the Radius of a Transiting Super-Earth
• Kepler-21b: A rocky planet around a V = 8.25 magnitude star
• Correlations between compositions and orbits established by the giant impact era of planet formation
• The 55 Cancri Planetary System: Fully Self-Consistent N-body Constraints and a Dynamical Analysis
• Three's Company: An additional non-transiting super-Earth in the bright HD 3167 system, and masses for all three planets
• Radial Velocity Planet Detection Biases at the Stellar Rotational Period
• The star formation in the L1615/L1616 cometary cloud
• Absence of a metallicity effect for ultra-short-period planets
• The transiting multi-planet system HD3167: a 5.7 MEarth Super-Earth and a 8.3 MEarth mini-Neptune
• Kepler-93b: A Terrestrial World Measured to within 120 km, and a Test Case for a New Spitzer Observing Mode
• Revised Masses and Densities of the Planets around Kepler-10
• Optimizing the search for transiting planets in long time series
• A low stellar obliquity for WASP-47, a compact multiplanet system with a hot Jupiter and an ultra-short period planet
• The K2-ESPRINT Project III: A Close-in Super-Earth around a Metal-rich Mid-M Dwarf
• The effect of ISM absorption on stellar activity measurements and its relevance for exoplanet studies

Cited by in corpus (48)

• Revisited Mass-Radius relations for exoplanets below 120 Earth masses
• An ultra-short period rocky super-Earth with a secondary eclipse and a Neptune-like companion around K2-141
• Kepler-78 and the Ultra-Short-Period Planets
• Cold Jupiters and improved masses in 38 Kepler and K2 small planet systems from 3661 HARPS-N radial velocities. No excess of cold Jupiters in small planet systems
• Homogeneous Analysis of Hot Earths: Masses, Sizes, and Compositions
• Discovery of a Third Transiting Planet in the Kepler-47 Circumbinary System
• 44 Validated Planets from K2 Campaign 10
• GJ 367b: A dense ultra-short period sub-Earth planet transiting a nearby red dwarf star
• The Habitable-zone Planet Finder Reveals A High Mass and a Low Obliquity for the Young Neptune K2-25b
• The Compositional Diversity of Low-Mass Exoplanets
• K2-141 b: A 5-M${}_{\oplus }$ super-Earth transiting a K7 V star every 6.7 hours
• Super-Earth of 8 Mearth in a 2.2-day orbit around the K5V star K2-216
• Overfitting Affects the Reliability of Radial Velocity Mass Estimates of the V1298 Tau Planets
• Lava Worlds: From Early Earth to Exoplanets
• TOI-257b (HD 19916b): A Warm sub-Saturn Orbiting an Evolved F-type Star
• K2-260 b: a hot Jupiter transiting an F star, and K2-261 b: a warm Saturn around a bright G star
• The TESS-Keck Survey II: An Ultra-Short Period Rocky Planet and its Siblings Transiting the Galactic Thick-Disk Star TOI-561
• GJ 1252 b: A 1.2 $R_{\oplus }$ planet transiting an M3-dwarf at 20.4 pc
• HD219666b: A hot-Neptune from TESS Sector 1
• Exoplanet Imitators: A test of stellar activity behavior in radial velocity signals
• TKS X: Confirmation of TOI-1444b and a Comparative Analysis of the Ultra-short-period Planets with Hot Neptunes
• K2-264: A transiting multi-planet system in the Praesepe open cluster
• HD 89345: a bright oscillating star hosting a transiting warm Saturn-sized planet observed by K2
• K2-290: a warm Jupiter and a mini-Neptune in a triple-star system
• 37 New Validated Planets in Overlapping K2 Campaigns
• Three small planets transiting the bright young field star K2-233
• Diffuser-assisted Photometric Follow-up Observations of the Neptune-sized Planets K2-28b and K2-100b
• Mass determination of the 1:3:5 near-resonant planets transiting GJ 9827 (K2-135)
• A Gaussian Process Regression Reveals No Evidence for Planets Orbiting Kapteyn's Star
• The TOI-763 system: sub-Neptunes orbiting a Sun-like star
• K2-155: A Bright Metal-Poor M Dwarf with Three Transiting Super-Earths
• Magellan/PFS Radial Velocities of GJ 9827, a late K dwarf at 30 pc with Three Transiting Super-Earths
• A Mini-Neptune Orbiting the Metal-poor K Dwarf BD+29 2654
• Probing Kepler's hottest small planets via homogeneous search and analysis of optical secondary eclipses and phase variations
• Joint Modeling of Radial Velocities and Photometry with a Gaussian Process Framework
• Two Planets Straddling the Habitable Zone of The Nearby K Dwarf Gl 414A
• Into the Depths: a new activity metric for high-precision radial velocity measurements based on line depth variations
• Revisiting the HD 21749 Planetary System with Stellar Activity Modeling
• The multi-planet system TOI-421 -- A warm Neptune and a super puffy mini-Neptune transiting a G9 V star in a visual binary
• Implications of an improved water equation of state for water-rich planets
• Hiding Planets Near and Far: The Parameter Space of Hidden Companions for Known Planetary Systems
• Quiet Please: Detrending Radial Velocity Variations from Stellar Activity with a Physically Motivated Spot Model
• The GALAH Survey: Improving our understanding of confirmed and candidate planetary systems with large stellar surveys
• Data Reduction Pipeline of the TOU Optical Very High Resolution Spectrograph and Its sub-m/s Performance
• A sub-Neptune transiting the young field star HD 18599 at 40 pc
• Surface pressure impact on nitrogen-dominated USP super-Earth atmospheres
• The Occurrence-weighted Median Planets Discovered by Transit Surveys Orbiting Solar-type Stars and Their Implications for Planet Formation and Evolution
• The impact of two non-transiting planets and stellar activity on mass determinations for the super-Earth CoRoT-7b