Characterization of the L 98-59 multi-planetary system with HARPS: two confirmed terrestrial planets and a mass upper limit on the third

Abstract

L 98-59 (TIC 307210830, TOI-175) is a nearby M3 dwarf around which TESS revealed three terrestrial-sized transiting planets (0.80, 1.35, 1.57 Earth radii) in a compact configuration with orbital periods shorter than 7.5 days. Here we aim to measure the masses of the known transiting planets in this system using precise radial velocity (RV) measurements taken with the HARPS spectrograph. We consider both trained and untrained Gaussian process regression models of stellar activity to simultaneously model the RV data with the planetary signals. Our RV analysis is then supplemented with dynamical simulations to provide strong constraints on the planets' orbital eccentricities by requiring long-term stability. We measure the planet masses of the two outermost planets to be $2.46\pm 0.31$ and $2.26\pm 0.50$ Earth masses which confirms their bulk terrestrial compositions. We are able to place an upper limit on the mass of the smallest, innermost planet of $<0.98$ Earth masses with 95% confidence. Our RV plus dynamical stability analysis places strong constraints on the orbital eccentricities and reveals that each planet's orbit likely has $e<0.1$ to ensure a dynamically stable system. The L 98-59 compact system of three likely rocky planets offers a unique laboratory for studies of planet formation, dynamical stability, and comparative atmospheric planetology. Continued RV monitoring will help refine the characterization of the innermost planet and potentially reveal additional planets in the system at wider separations.

arXiv commentSubmitted to the A&A journal. 12 pages, 7 figures, 4 tables. Comments welcome

References in corpus (69)

• emcee: The MCMC Hammer
• Gaia Data Release 2. Summary of the contents and survey properties
• Gaia Data Release 2: The astrometric solution
• The generalised Lomb-Scargle periodogram. A new formalism for the floating-mean and Keplerian periodograms
• REBOUND: An open-source multi-purpose N-body code for collisional dynamics
• Kepler planets: a tale of evaporation
• Architecture and Dynamics of Kepler's Candidate Multiple Transiting Planet Systems
• No planet for HD 166435
• The evaporation valley in the Kepler planets
• Gaia Data Release 2: Photometric content and validation
• Architecture of Kepler's Multi-transiting Systems: II. New investigations with twice as many candidates
• How to Constrain Your M Dwarf: measuring effective temperature, bolometric luminosity, mass, and radius
• The TESS Input Catalog and Candidate Target List
• Understanding the Mass-Radius Relation for Sub-Neptunes: Radius as a Proxy for Composition
• Probabilistic Forecasting of the Masses and Radii of Other Worlds
• A Framework for Prioritizing the TESS Planetary Candidates Most Amenable to Atmospheric Characterization
• The Transiting Exoplanet Survey Satellite: Simulations of planet detections and astrophysical false positives
• Improving the Efficiency of Markov Chain Monte Carlo for Analyzing the Orbits of Extrasolar Planets
• WHFast: A fast and unbiased implementation of a symplectic Wisdom-Holman integrator for long term gravitational simulations
• How to Constrain Your M dwarf II: the mass-luminosity-metallicity relation from 0.075 to 0.70$M_{\odot }$
• Planetary population synthesis coupled with atmospheric escape: a statistical view of evaporation
• A temperate rocky super-Earth transiting a nearby cool star
• Kepler Data Validation I -- Architecture, Diagnostic Tests, and Data Products for Vetting Transiting Planet Candidates
• A new list of thorium and argon spectral lines in the visible
• Eccentricity from transit photometry: small planets in Kepler multi-planet systems have low eccentricities
• A Revised Exoplanet Yield from the Transiting Exoplanet Survey Satellite (TESS)
• The rotation and Galactic kinematics of mid M dwarfs in the Solar Neighborhood
• A Detailed Model Grid for Solid Planets from 0.1 through 100 Earth Masses
• Kepler Data Validation II -- Transit Model Fitting and Multiple-Planet Search
• Densities and Eccentricities of 139 Kepler Planets from Transit Time Variations
• Observing the Atmospheres of Known Temperate Earth-sized Planets with JWST
• Evolutionary Analysis of Gaseous Sub-Neptune-Mass Planets with MESA
• The Solar Neighborhood XXXVII: The Mass-Luminosity Relation for Main Sequence M Dwarfs
• Search for exoplanets with the radial-velocity technique: quantitative diagnostics of stellar activity
• TESS Discovery of a Transiting Super-Earth in the $\pi$ Mensae System
• Magnetic activity in the HARPS M-dwarf sample. The rotation-activity relationship for very low-mass stars through R'HK
• The fundamental definition of 'radial velocity'
• A Kepler Study of Starspot Lifetimes with Respect to Light Curve Amplitude and Spectral Type
• TESS Discovery of an ultra-short-period planet around the nearby M dwarf LHS 3844
• The HARPS search for southern extra-solar planets XLI. A dozen planets around the M dwarfs GJ 3138, GJ 3323, GJ 273, GJ 628, and GJ 3293
• How formation time-scales affect the period dependence of the transition between rocky super-Earths and gaseous sub-Neptunes and implications for ${\eta }_{\oplus }$
• Stability Limits in Extra-solar Planetary Systems
• The L 98-59 System: Three Transiting, Terrestrial-Sized Planets Orbiting a Nearby M-dwarf
• Planetary system around the nearby M dwarf GJ 357 including a transiting, hot, Earth-sized planet optimal for atmospheric characterization
• TESS's first planet: a super-Earth transiting the naked-eye star $\pi$ Mensae
• Long-term magnetic activity of a sample of M-dwarf stars from the HARPS program II. Activity and radial velocity
• A Catalog of Cool Dwarf Targets for the Transiting Exoplanet Survey Satellite
• A second terrestrial planet orbiting the nearby M dwarf LHS 1140
• Characterization of the K2-18 multi-planetary system with HARPS: A habitable zone super-Earth and discovery of a second, warm super-Earth on a non-coplanar orbit
• On the use of marginal posteriors in marginal likelihood estimation via importance-sampling
• Radial Velocity Planet Detection Biases at the Stellar Rotational Period
• HD 202772A B: A Transiting Hot Jupiter Around A Bright, Mildly Evolved Star In A Visual Binary Discovered By Tess
• TESS delivers its first Earth-sized planet and a warm sub-Neptune
• Confirmation of the radial velocity super-Earth K2-18c with HARPS and CARMENES
• Radial velocity follow-up of GJ1132 with HARPS. A precise mass for planet 'b' and the discovery of a second planet
• Simulated JWST/NIRISS Transit Spectroscopy of Anticipated TESS Planets Compared to Select Discoveries from Space-Based and Ground-Based Surveys
• Predicted Number, Multiplicity, and Orbital Dynamics of TESS M Dwarf Exoplanets
• The HARPS search for southern extra-solar planets XLII. A system of Earth-mass planets around the nearby M dwarf YZ Ceti
• HD 213885b: A transiting 1-day-period super-Earth with an Earth-like composition around a bright ($V=7.9$) star unveiled by TESS
• HD 1397b: a transiting warm giant planet orbiting a V = 7.8 mag sub-giant star discovered by TESS
• An Eccentric Massive Jupiter Orbiting a Sub-Giant on a 9.5 Day Period Discovered in the Transiting Exoplanet Survey Satellite Full Frame Images
• A Jovian planet in an eccentric 11.5 day orbit around HD1397 discovered by TESS
• HD2685 b: A Hot-Jupiter orbiting an early F-type star detected by TESS
• Hot, rocky and warm, puffy super-Earths orbiting TOI-402 (HD 15337)
• A resonant pair of warm giant planets revealed by TESS
• Quantifying the Observational Effort Required for the Radial Velocity Characterization of TESS Planets
• Expected Yields of Planet discoveries from the TESS primary and extended missions
• TOI-150: A transiting hot Jupiter in the TESS southern CVZ
• The independent discovery of planet candidates around low mass stars and astrophysical false positives from the first two TESS sectors

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• L 98-59: a Benchmark System of Small Planets for Future Atmospheric Characterization