A transiting rocky super-Earth and a non-transiting sub-Neptune orbiting the M dwarf TOI-771

Abstract

The origin and evolution of the sub-Neptune population is a highly debated topic in the exoplanet community. With the advent of JWST, atmospheric studies can now put unprecedented constraints on the internal composition of this population. In this context, the THIRSTEE project aims to investigate the population properties of sub-Neptunes with a comprehensive and demographic approach, providing a homogeneous sample of precisely characterised sub-Neptunes across stellar spectral types. We present here the precise characterisation of the planetary system orbiting one of the THIRSTEE M-dwarf targets, TOI-771 (V = 14.9 mag), known to host one planet, TOI-771 b, which has been statistically validated using TESS observations. We use TESS, SPECULOOS, TRAPPIST and M-Earth photometry together with 31 high-precision ESPRESSO radial velocities to derive the orbital parameters and investigate the internal composition of TOI-771 b, as well as exploring the presence of additional companions in the system. We derive precise mass and radius for TOI-771 b, a super-Earth with R_b = 1.36 +/- 0.10 R_e and M_b = 2.47 +/- 0.32 M_e orbiting at 2.3 d. Its composition is consistent with an Earth-like planet, and it adds up to the rocky population of sub-Neptunes lying below the density gap identified around M dwarfs. With a 13% precision in mass, a 7% radius precision, and a warm equilibrium temperature of T_eq= 543 K, TOI-771 b is a particularly interesting target for atmospheric characterisation, and it is indeed one of the targets under consideration for the Rocky World DDT program. Additionally, we discover the presence of a second, non-transiting planet, TOI-771 c, with a period of 7.6 d and a minimum mass of Mp sin(i) = 2.9 +/- 0.4 M_e. Even though the inclination is not directly constrained, the planet likely belongs to the temperate sub-Neptune population, with an equilibrium temperature of 365 K.

20 pages, 17 figures. Accepted for publication in A&A

References in corpus (63)

• The Gaia mission
• Gaia Data Release 3: Summary of the content and survey properties
• The Transiting Exoplanet Survey Satellite
• The generalised Lomb-Scargle periodogram. A new formalism for the floating-mean and Keplerian periodograms
• The All-Sky Automated Survey for Supernovae (ASAS-SN) Light Curve Server v1.0
• DHP Framework: Digital Health Passports Using Blockchain -- Use case on international tourism during the COVID-19 pandemic
• EXOFAST: A fast exoplanetary fitting suite in IDL
• VOSA: Virtual Observatory SED Analyzer. An application to the Collinder 69 open cluster
• Growth Model Interpretation of Planet Size Distribution
• Spectrum radial velocity analyser (SERVAL). High-precision radial velocities and two alternative spectral indicators
• The TESS Objects of Interest Catalog from the TESS Prime Mission
• Three regimes of extrasolar planets inferred from host star metallicities
• Density, not radius, separates rocky and water-rich small planets orbiting M dwarf stars
• Revisited Mass-Radius relations for exoplanets below 120 Earth masses
• Magnetic Cycles and Rotation Periods of Late Type Stars from photometric time series
• The New Generation Planetary Population Synthesis (NGPPS). IV. Planetary systems around low-mass stars
• The CARMENES search for exoplanets around M dwarfs: Different roads to radii and masses of the target stars
• High Tide or Riptide on the Cosmic Shoreline? A Water-Rich Atmosphere or Stellar Contamination for the Warm Super-Earth GJ~486b from JWST Observations
• Kepler Multi-Planet Systems Exhibit Unexpected Intra-system Uniformity in Mass and Radius
• The California-Kepler Survey. X. The Radius Gap as a Function of Stellar Mass, Metallicity, and Age
• Stellar chromospheric activity of 1,674 FGK stars from the AMBRE-HARPS sample I. A catalogue of homogeneous chromospheric activity
• Mass-radius relationships for irradiated ocean planets
• The Precision of Mass Measurements Required for Robust Atmospheric Characterization of Transiting Exoplanets
• The CARMENES search for exoplanets around M dwarfs. Stellar atmospheric parameters of target stars with SteParSyn
• Conclusive evidence for a population of water-worlds around M-dwarfs remains elusive
• A super-Earth and a sub-Neptune orbiting the bright, quiet M3 dwarf TOI-1266
• Sulphur dioxide in the mid-infrared transmission spectrum of WASP-39b
• The Monitor project: Data processing and lightcurve production
• JWST/NIRISS reveals the water-rich "steam world" atmosphere of GJ 9827 d
• Rocky super-Earths or waterworlds: the interplay of planet migration, pebble accretion and disc evolution
• Radial Velocity Data Analysis with Compressed Sensing Techniques
• The Exoplanet Radius Valley from Gas-driven Planet Migration and Breaking of Resonant Chains
• The HARPS search for southern extra-solar planets XLII. A system of Earth-mass planets around the nearby M dwarf YZ Ceti
• Majority of water hides deep in the interiors of exoplanets
• Two temperate super-Earths transiting a nearby late-type M dwarf
• From super-Earths to sub-Neptunes: Observational constraints and connections to theoretical models
• prose: A Python framework for modular astronomical images processing
• A Benchmark JWST Near-Infrared Spectrum for the Exoplanet WASP-39b
• A fading radius valley towards M-dwarfs, a persistent density valley across stellar types
• SteParSyn: A Bayesian code to infer stellar atmospheric parameters using spectral synthesis
• Pebbles versus planetesimals: the outcomes of population synthesis models
• GJ 273: On the formation, dynamical evolution and habitability of a planetary system hosted by an M dwarf at 3.75 parsec
• TOI-1235 b: a keystone super-Earth for testing radius valley emergence models around early M dwarfs
• TOI-431/HIP 26013: a super-Earth and a sub-Neptune transiting a bright, early K dwarf, with a third RV planet
• ExoMDN: Rapid characterization of exoplanet interior structures with Mixture Density Networks
• Investigating the architecture and internal structure of the TOI-561 system planets with CHEOPS, HARPS-N and TESS
• The K2-3 system revisited: testing photoevaporation and core-powered mass loss with three small planets spanning the radius valley
• The Reversibility Error Method (REM): a new, dynamical fast indicator for planetary dynamics
• The CARMENES search for exoplanets around M dwarfs: Benchmarking the impact of activity in high-precision radial velocity measurements
• A super-Earth and a mini-Neptune near the 2:1 MMR straddling the radius valley around the nearby mid-M dwarf TOI-2096
• HD 191939 revisited: New and refined planet mass determinations, and a new planet in the habitable zone
• Phase curve pollution of exoplanet transmission spectra
• A HARPS-N mass for the elusive Kepler-37d: a case study in disentangling stellar activity and planetary signals
• Revisiting K2-233 spectroscopic time-series with multidimensional Gaussian Processes
• Where are the Water Worlds?: Self-Consistent Models of Water-Rich Exoplanet Atmospheres
• Generalized Peas-in-a-Pod: Extending Intra-System Mass Uniformity to Non-TTV Systems via the Gini Index
• Precise mass determination for the keystone sub-Neptune planet transiting the mid-type M dwarf G 9-40
• The SHERLOCK pipeline: new exoplanet candidates in the WASP-16, HAT-P-27, HAT-P-26, and TOI-2411 systems
• Detecting Biosignatures in the Atmospheres of Gas Dwarf Planets with the James Webb Space Telescope
• Detection of an Earth-sized exoplanet orbiting the nearby ultracool dwarf star SPECULOOS-3
• TOI-4438 b: a transiting mini-Neptune amenable to atmospheric characterization
• Characterisation of TOI-406 as showcase of the THIRSTEE program: A 2-planet system straddling the M-dwarf density gap
• A Gap in the Densities of Small Planets Orbiting M Dwarfs: Rigorous Statistical Confirmation Using the Open-source Code RhoPop

Cited by in corpus (1)

• Sibling Sub-Neptunes Around Sibling M Dwarfs: TOI-521 and TOI-912