K2-291 b: A rocky super-Earth in a 2.2 day orbit

Abstract

K2-291 (EPIC 247418783) is a solar-type star with a radius of R_star = 0.899 $\pm$ 0.034 R_sun and mass of M_star=0.934 $\pm$ 0.038 M_sun. From K2 C13 data, we found one super-Earth planet (R_p = 1.589+0.095-0.072 R_Earth) transiting this star on a short period orbit (P = 2.225177 +6.6e-5 -6.8e-5 days). We followed this system up with adaptive-optic imaging and spectroscopy to derive stellar parameters, search for stellar companions, and determine a planet mass. From our 75 radial velocity measurements using HIRES on Keck I and HARPS-N on Telescopio Nazionale Galileo, we constrained the mass of EPIC 247418783b to M_p = 6.49 $\pm$ 1.16 M_Earth. We found it necessary to model correlated stellar activity radial velocity signals with a Gaussian process in order to more accurately model the effect of stellar noise on our data; the addition of the Gaussian process also improved the precision of this mass measurement. With a bulk density of 8.84+2.50-2.03 g cm-3, the planet is consistent with an Earth-like rock/iron composition and no substantial gaseous envelope. Such an envelope, if it existed in the past, was likely eroded away by photo-evaporation during the first billion years of the star's lifetime.

arXiv commentAccepted to AJ, 15 pages, 8 figures

References in corpus (40)

• emcee: The MCMC Hammer
• Gaia Data Release 2. Summary of the contents and survey properties
• MESA Isochrones and Stellar Tracks (MIST). I: Solar-Scaled Models
• MESA Isochrones and Stellar Tracks (MIST) 0: Methods for the construction of stellar isochrones
• The California-Kepler Survey. III. A Gap in the Radius Distribution of Small Planets
• batman: BAsic Transit Model cAlculatioN in Python
• Planetary Radii across Five Orders of Magnitude in Mass and Stellar Insolation: Application to Transits
• Kepler planets: a tale of evaporation
• Most 1.6 Earth-Radius Planets are not Rocky
• Understanding the Mass-Radius Relation for Sub-Neptunes: Radius as a Proxy for Composition
• The Mass-Radius Relation for 65 Exoplanets Smaller than 4 Earth Radii
• RadVel: The Radial Velocity Modeling Toolkit
• The California Kepler Survey VII. Precise Planet Radii Leveraging Gaia DR2 Reveal the Stellar Mass Dependence of the Planet Radius Gap
• Planets and Stellar Activity: Hide and Seek in the CoRoT-7 system
• The Role of Core Mass in Controlling Evaporation: the Kepler Radius Distribution and the Kepler-36 Density Dichotomy
• Chromospheric Activity and Jitter Measurements for 2630 Stars on the California Planet Search
• Masses, Radii, and Orbits of Small Kepler Planets: The Transition from Gaseous to Rocky Planets
• Galactic Reddening in 3D from Stellar Photometry - An Improved Map
• Mass-Radius Relation for Rocky Planets based on PREM
• The California Planet Survey I. Four New Giant Exoplanets
• A Gaussian process framework for modelling stellar activity signals in radial velocity data
• Spectroscopy Made Easy: Evolution
• Spectral Properties of Cool Stars: Extended Abundance Analysis of 1617 Planet Search Stars
• Planetary detection limits taking into account stellar noise. I. Observational strategies to reduce stellar oscillation and granulation effects
• Asteroseismology and Gaia: Testing Scaling Relations Using 2200 Kepler Stars with TGAS Parallaxes
• 197 Candidates and 104 Validated Planets in K2's First Five Fields
• K2SC: Flexible systematics correction and detrending of K2 light curves using Gaussian Process regression
• Determining the Mass of Kepler-78b With Nonparametric Gaussian Process Estimation
• The DECam Plane Survey: Optical photometry of two billion objects in the southern Galactic plane
• Zodiacal Exoplanets in Time (ZEIT) IV: seven transiting planets in the Praesepe cluster
• The GAPS programme with HARPS-N at TNG XI. Pr~0211 in M~44: the first multi-planet system in an open cluster
• An ultra-short period rocky super-Earth with a secondary eclipse and a Neptune-like companion around K2-141
• Kepler-21b: A rocky planet around a V = 8.25 magnitude star
• Uncovering the planets and stellar activity of CoRoT-7 using only radial velocities
• Two Transiting Earth-size Planets Near Resonance Orbiting a Nearby Cool Star
• Detection of Stars within $\sim$0.8 arcseconds of Kepler Objects of Interest
• Planet Candidates from K2 Campaigns 5-8 and Follow-Up Optical Spectroscopy
• Discovery of a Transiting Adolescent Sub-Neptune Exoplanet with K2
• A pragmatic Bayesian perspective on correlation analysis: The exoplanetary gravity - stellar activity case
• An accurate mass determination for Kepler-1655b, a moderately-irradiated world with a significant volatile envelope

Cited by in corpus (12)

• Revisited Mass-Radius relations for exoplanets below 120 Earth masses
• Homogeneous Analysis of Hot Earths: Masses, Sizes, and Compositions
• Chemical Fingerprints of Formation in Rocky Super-Earths' Data
• TKS X: Confirmation of TOI-1444b and a Comparative Analysis of the Ultra-short-period Planets with Hot Neptunes
• Photometry as a proxy for stellar activity in radial velocity analyses
• Forming Iron-rich Planets with Giant Impacts
• A Gaussian Process Regression Reveals No Evidence for Planets Orbiting Kapteyn's Star
• Rotation periods of TESS Objects of Interest from the Magellan-TESS Survey with multiband photometry from Evryscope and TESS
• A Gap in the Mass Distribution for Warm Neptune and Terrestrial Planets
• Kepler-102: Masses and Compositions for a Super-Earth and Sub-Neptune Orbiting an Active Star
• HyDRo: Atmospheric Retrieval of Rocky Exoplanets in Thermal Emission
• The Occurrence-weighted Median Planets Discovered by Transit Surveys Orbiting Solar-type Stars and Their Implications for Planet Formation and Evolution