Three small planets transiting the bright young field star K2-233

Abstract

We report the detection of three small transiting planets around the young K3 dwarf K2-233 (2MASS J15215519-2013539) from observations during Campaign 15 of the K2 mission. The star is relatively nearby ($d$ = 69 pc) and bright ($V$ = 10.7 mag, $K_s$ = 8.4 mag), making the planetary system an attractive target for radial velocity follow-up and atmospheric characterization with the James Webb Space Telescope. The inner two planets are hot super-Earths ($R_b$ = 1.40 $\pm$ 0.06 R${}_{\oplus }$, $R_c$ = 1.34 $\pm$ 0.08 R${}_{\oplus }$), while the outer planet is a warm sub-Neptune ($R_d$ = 2.6 $\pm$ 0.1 R${}_{\oplus }$). We estimate the stellar age to be 360${}_{-140}^{+490}$ Myr based on rotation, activity, and kinematic indicators. The K2-233 system is particularly interesting given recent evidence for inflated radii in planets around similarly-aged stars, a trend potentially related to photo-evaporation, core-cooling, or both mechanisms.

arXiv commentAccepted to AJ. 15 pages, 6 figures, 3 tables

References in corpus (48)

• emcee: The MCMC Hammer
• The K2 Mission: Characterization and Early results
• The California-Kepler Survey. III. A Gap in the Radius Distribution of Small Planets
• Improved Age Estimation for Solar-Type Dwarfs Using Activity-Rotation Diagnostics
• Planet Occurrence within 0.25 AU of Solar-type Stars from Kepler
• The NASA Exoplanet Archive: Data and Tools for Exoplanet Research
• Ages for illustrative field stars using gyrochronology: viability, limitations and errors
• Prevalence of Earth-size planets orbiting Sun-like stars
• Architecture of Kepler's Multi-transiting Systems: II. New investigations with twice as many candidates
• Probabilistic Forecasting of the Masses and Radii of Other Worlds
• BANYAN. XI. The BANYAN $\Sigma$ multivariate Bayesian algorithm to identify members of young associations within 150 pc
• 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
• A disintegrating minor planet transiting a white dwarf
• Atmospheric Retrieval for Super-Earths: Uniquely Constraining the Atmospheric Composition with Transmission Spectroscopy
• The California Planet Survey I. Four New Giant Exoplanets
• A library of high resolution synthetic stellar spectra from 300nm to 1.8 micron with solar and alpha-enhanced composition
• The California-Kepler Survey V. Peas in a Pod: Planets in a Kepler Multi-planet System are Similar in Size and Regularly Spaced
• Precision Stellar Characterization of FGKM Stars using an Empirical Spectral Library
• Eccentricity from transit photometry: small planets in Kepler multi-planet systems have low eccentricities
• Understanding The Effects Of Stellar Multiplicity On The Derived Planet Radii From Transit Surveys: Implications for Kepler, K2, and TESS
• Asteroseismology and Gaia: Testing Scaling Relations Using 2200 Kepler Stars with TGAS Parallaxes
• Probabilistic Mass-Radius Relationship for Sub-Neptune-Sized Planets
• A Plateau in the Planet Population Below Twice the Size of Earth
• Densities and Eccentricities of 139 Kepler Planets from Transit Time Variations
• Exoplanet Orbital Eccentricities Derived From LAMOST-Kepler Analysis
• PyTransit: Fast and Easy Exoplanet Transit Modelling in Python
• Rotation in the Pleiades with K2: I. Data and First Results
• 197 Candidates and 104 Validated Planets in K2's First Five Fields
• Calibrating Gyrochronology using Kepler Asteroseismic targets
• Kepler Multi-Planet Systems Exhibit Unexpected Intra-system Uniformity in Mass and Radius
• On The Relative Sizes of Planets Within Kepler Multiple Candidate Systems
• Rotation of Late-Type Stars in Praesepe with K2
• Zodiacal Exoplanets in Time (ZEIT) V: A Uniform Search for Transiting Planets in Young Clusters Observed by K2
• Detection of Stars within $\sim$0.8 arcseconds of Kepler Objects of Interest
• The transiting multi-planet system HD3167: a 5.7 MEarth Super-Earth and a 8.3 MEarth mini-Neptune
• The K2-138 System: A Near-Resonant Chain of Five Sub-Neptune Planets Discovered by Citizen Scientists
• Five Planets Transiting a Ninth Magnitude Star
• Two Small Planets Transiting HD 3167
• The discovery and mass measurement of a new ultra-short-period planet: EPIC~228732031b
• Three Small Super-Earths Transiting the nearby star GJ 9827
• Zodiacal Exoplanets in Time (ZEIT) II. A "Super-Earth" Orbiting a Young K Dwarf in the Pleiades Neighborhood
• Two Small Transiting Planets and a Possible Third Body Orbiting HD 106315
• A Multi-Planet System Transiting the $V$ = 9 Rapidly Rotating F-Star HD 106315
• Identifying Young $Kepler$ Planet Host Stars from Keck-HIRES Spectra of Lithium
• A System of Three Super Earths Transiting the Late K-Dwarf GJ 9827 at Thirty Parsecs
• K2 reveals pulsed accretion driven by the 2 Myr old hot Jupiter CI Tau b
• K2-139 b: a low-mass warm Jupiter on a 29-day orbit transiting an active K0 V star

Cited by in corpus (21)

• TESS Hunt for Young and Maturing Exoplanets (THYME) III: a two-planet system in the 400 Myr Ursa Major Group
• ExoClock Project III: 450 new exoplanet ephemerides from ground and space observations
• Machine-learning Approaches to Exoplanet Transit Detection and Candidate Validation in Wide-field Ground-based Surveys
• TESS Hunt for Young and Maturing Exoplanets (THYME) V: A Sub-Neptune Transiting a Young Star in a Newly Discovered 250 Myr Association
• Two young planetary systems around field stars with ages between 20-320 Myr from TESS
• Photodynamical analysis of the triply eclipsing hierarchical triple system EPIC 249432662
• A Compact Multi-Planet System With A Significantly Misaligned Ultra Short Period Planet
• Discovery of a Transiting Adolescent Sub-Neptune Exoplanet with K2
• Masses for the seven planets in K2-32 and K2-233. Four diverse planets in resonant chain and the first young rocky worlds
• A TESS Dress Rehearsal: Planetary Candidates and Variables from K2 Campaign 17
• A Mini-Neptune from TESS and CHEOPS Around the 120 Myr Old AB Dor member HIP 94235
• Revisiting K2-233 spectroscopic time-series with multidimensional Gaussian Processes
• Probing Transit Timing Variation and its Possible Origin with Twelve New Transits of TrES-3b
• K2-288Bb: A Small Temperate Planet in a Low-mass Binary System Discovered by Citizen Scientists
• Planetary candidates transiting cool dwarf stars from Campaigns 12 to 15 of K2
• TOI-1801 b: A temperate mini-Neptune around a young M0.5 dwarf
• TOI-837b is a Young Saturn-sized Exoplanet with a Massive 70 $M_{\oplus }$ Core
• Dynamical masses of two young transiting sub-Neptunes orbiting HD 63433
• PPMXL and Gaia Morphological Analysis of Melotte 22 (Pleaides) and 25 (Hyades)
• A search for stellar siblings of the ~ 200 Myr TOI-251b planetary system
• The Visual Survey Group: A Decade of Hunting Exoplanets and Unusual Stellar Events with Space-Based Telescopes