Revisiting K2-233 spectroscopic time-series with multidimensional Gaussian Processes

Abstract

Detecting planetary signatures in radial velocity time-series of young stars is challenging due to their inherently strong stellar activity. However, it is possible to learn information about the properties of the stellar signal by using activity indicators measured from the same stellar spectra used to extract radial velocities. In this manuscript, we present a reanalysis of spectroscopic HARPS data of the young star K2-233, which hosts three transiting planets. We perform a multidimensional Gaussian Process regression on the radial velocity and the activity indicators to characterise the planetary Doppler signals. We demonstrate, for the first time on a real dataset, that the use of a multidimensional Gaussian Process can boost the precision with which we measure the planetary signals compared to a one-dimensional Gaussian Process applied to the radial velocities alone. We measure the semi-amplitudes of K2-233 b, c, and d as 1.31(-0.74)(+0.81), 1.81(-0.67)(+0.71), and 2.72(-0.70)(+0.66) m/s, which translates into planetary masses of 2.4(-1.3)(+1.5), 4.6(-1.7)(+1.8), and 10.3(-2.6)(+2.4), respectively. These new mass measurements make K2-233 d a valuable target for transmission spectroscopy observations with JWST. K2-233 is the only young system with two detected inner planets below the radius valley and a third outer planet above it. This makes it an excellent target to perform comparative studies, to inform our theories of planet evolution, formation, migration, and atmospheric evolution.

arXiv commentAccepted for publication in MNRAS

References in corpus (77)

• Array Programming with NumPy
• Astropy: A Community Python Package for Astronomy
• emcee: The MCMC Hammer
• The Astropy Project: Building an inclusive, open-science project and status of the v2.0 core package
• The Astropy Project: Sustaining and Growing a Community-oriented Open-source Project and the Latest Major Release (v5.0) of the Core Package
• The Transiting Exoplanet Survey Satellite
• 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
• Clouds in the atmosphere of the super-Earth exoplanet GJ 1214b
• Efficient, uninformative sampling of limb darkening coefficients for two-parameter laws
• The NASA Exoplanet Archive: Data and Tools for Exoplanet Research
• Kepler planets: a tale of evaporation
• No planet for HD 166435
• The evaporation valley in the Kepler planets
• Planet-disk interaction and orbital evolution
• 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
• A Framework for Prioritizing the TESS Planetary Candidates Most Amenable to Atmospheric Characterization
• The CORALIE survey for southern extra-solar planets VII. Two short-period Saturnian companions to HD108147 and HD168746
• RadVel: The Radial Velocity Modeling Toolkit
• Planets and Stellar Activity: Hide and Seek in the CoRoT-7 system
• An asteroseismic view of the radius valley: stripped cores, not born rocky
• Mass-Radius Relation for Rocky Planets based on PREM
• A Gaussian process framework for modelling stellar activity signals in radial velocity data
• Sculpting the Valley in the Radius Distribution of Small Exoplanets as a by-product of Planet Formation: The Core-Powered Mass-Loss Mechanism
• A featureless transmission spectrum for the Neptune-mass exoplanet GJ 436b
• A new list of thorium and argon spectral lines in the visible
• Binning is sinning: morphological light-curve distortions due to finite integration time
• A simple method to estimate radial velocity variations due to stellar activity using photometry
• Compositional diversity in the atmospheres of hot Neptunes, with application to GJ 436b
• Water Vapor and Clouds on the Habitable-Zone Sub-Neptune Exoplanet K2-18b
• Super-Earth Atmospheres: Self-Consistent Gas Accretion and Retention
• The CHEOPS mission
• The Next Generation Transit Survey (NGTS)
• SOAP 2.0: A tool to estimate the photometric and radial velocity variations induced by stellar spots and plages
• The orbital eccentricity of small planet systems
• Stellar activity of planetary host star HD 189733
• Long-term magnetic activity of a sample of M-dwarf stars from the HARPS program I. Comparison of activity indices
• Long Term Evolution of Close Planets Including the Effects of Secular Interactions
• Zodiacal Exoplanets in Time (ZEIT) III: A short-period planet orbiting a pre-main-sequence star in the Upper Scorpius OB Association
• TESS Hunt for Young and Maturing Exoplanets (THYME): A planet in the 45 Myr Tucana-Horologium association
• Determining the Mass of Kepler-78b With Nonparametric Gaussian Process Estimation
• Zodiacal Exoplanets In Time (ZEIT) I: A Neptune-sized planet orbiting an M4.5 dwarf in the Hyades Star Cluster
• The nature and origins of sub-Neptune size planets
• The California-Kepler Survey. X. The Radius Gap as a Function of Stellar Mass, Metallicity, and Age
• A method for the direct determination of the surface gravities of transiting extrasolar planets
• The Precision of Mass Measurements Required for Robust Atmospheric Characterization of Transiting Exoplanets
• New constraints on the planetary system around the young active star AU Mic. Two transiting warm Neptunes near mean-motion resonance
• TESS Hunt for Young and Maturing Exoplanets (THYME) II: A 17 Myr Old Transiting Hot Jupiter in the Sco-Cen Association
• Planet-planet scattering leads to tightly packed planetary systems
• Pyaneti: a fast and powerful software suite for multi-planet radial velocity and transit fitting
• pyaneti II: A multidimensional Gaussian process approach to analysing spectroscopic time-series
• Homogeneous Analysis of Hot Earths: Masses, Sizes, and Compositions
• Hydrodynamic Simulations of Unevenly Irradiated Jovian Planets
• TESS Hunt for Young and Maturing Exoplanets (THYME) VI: an 11 Myr giant planet transiting a very low-mass star in Lower Centaurus Crux
• Eccentricity evolution during planet-disc interaction
• Rapid contraction of giant planets orbiting the 20 million-years old star V1298 Tau
• Radial velocity confirmation of K2-100b: a young, highly irradiated, and low density transiting hot Neptune
• K2-141 b: A 5-M${}_{\oplus }$ super-Earth transiting a K7 V star every 6.7 hours
• One year of AU Mic with HARPS: II -- stellar activity and star-planet interaction
• The Na I D resonance lines in main sequence late-type stars
• TESS Hunt for Young and Maturing Exoplanets (THYME) IV: Three small planets orbiting a 120 Myr-old star in the Pisces--Eridanus stream
• Cluster Difference Imaging Photometric Survey. II. TOI 837: A Young Validated Planet in IC 2602
• One year of AU Mic with HARPS: I -- measuring the masses of the two transiting planets
• The young HD 73583 (TOI-560) planetary system: Two 10-M${}_{\oplus }$ mini-Neptunes transiting a 500-Myr-old, bright, and active K dwarf
• A transiting warm giant planet around the young active star TOI-201
• Quasi-periodic Gaussian Processes for stellar activity: from physical to kernel parameters
• The GAPS Programme with HARPS-N at TNG. XXXVII. A precise density measurement of the young ultra-short period planet TOI-1807 b
• Caught in the Act: Core-powered Mass-loss Predictions for Observing Atmospheric Escape
• Understanding stellar activity-induced radial velocity jitter using simultaneous K2 photometry and HARPS RV measurements
• Masses for the seven planets in K2-32 and K2-233. Four diverse planets in resonant chain and the first young rocky worlds
• The HARPS search for southern extra-solar planets XLV. Two Neptune mass planets orbiting HD 13808: a study of stellar activity modelling's impact on planet detection
• A HARPS-N mass for the elusive Kepler-37d: a case study in disentangling stellar activity and planetary signals
• Three small planets transiting the bright young field star K2-233
• An 11 Earth-Mass, Long-Period Sub-Neptune Orbiting a Sun-like Star
• Evidence that Core-Powered Mass-Loss Dominates Over Photoevaporation in Shaping the Kepler Radius Valley

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• HADES RV Programme with HARPS-N at TNG. XVI. A super-Earth in the habitable zone of the GJ 3998 multi-planet system
• The GAPS Programme at TNG. LIX. A characterisation study of the $\sim$300 Myr old multi-planetary system orbiting the star BD+40 2790 (TOI-2076)
• A transiting rocky super-Earth and a non-transiting sub-Neptune orbiting the M dwarf TOI-771
• The RoPES project with HARPS and HARPS-N II. A third planet in the multi-planet system HD 176986
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• Sibling Sub-Neptunes Around Sibling M Dwarfs: TOI-521 and TOI-912
• Improving exoplanet mass characterisation with Bayesian model selection using the Learned Harmonic Mean Estimator
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