A 1.55 R${}_{\oplus }$ habitable-zone planet hosted by TOI-715, an M4 star near the ecliptic South Pole

Abstract

A new generation of observatories is enabling detailed study of exoplanetary atmospheres and the diversity of alien climates, allowing us to seek evidence for extraterrestrial biological and geological processes. Now is therefore the time to identify the most unique planets to be characterised with these instruments. In this context, we report on the discovery and validation of TOI-715 b, a $R_{\mathrm{b}}=1.55\pm 0.06{\mathrm{R}}_{\oplus }$ planet orbiting its nearby ($42$ pc) M4 host (TOI-715/TIC 271971130) with a period $P_{\mathrm{b}}=19.288004_{-0.000024}^{+0.000027}$ days. TOI-715 b was first identified by TESS and validated using ground-based photometry, high-resolution imaging and statistical validation. The planet's orbital period combined with the stellar effective temperature $T_{\mathrm{eff}}=3075\pm 75\mathrm{K}$ give this planet an instellation $S_{\mathrm{b}}=0.67_{-0.20}^{+0.15}{\mathrm{S}}_{\oplus }$, placing it within the most conservative definitions of the habitable zone for rocky planets. TOI-715 b's radius falls exactly between two measured locations of the M-dwarf radius valley; characterising its mass and composition will help understand the true nature of the radius valley for low-mass stars. We demonstrate TOI-715 b is amenable for characterisation using precise radial velocities and transmission spectroscopy. Additionally, we reveal a second candidate planet in the system, TIC 271971130.02, with a potential orbital period of $P_{02}=25.60712_{-0.00036}^{+0.00031}$ days and a radius of $R_{02}=1.066\pm 0.092{\mathrm{R}}_{\oplus }$, just inside the outer boundary of the habitable zone, and near a 4:3 orbital period commensurability. Should this second planet be confirmed, it would represent the smallest habitable zone planet discovered by TESS to date.

arXiv commentAccepted for publication in MNRAS

References in corpus (133)

• 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
• dynesty: A Dynamic Nested Sampling Package for Estimating Bayesian Posteriors and Evidences
• A new extensive library of PHOENIX stellar atmospheres and synthetic spectra
• Estimating distances from parallaxes. V: Geometric and photogeometric distances to 1.47 billion stars in Gaia Early Data Release 3
• Habitable Zones Around Main-Sequence Stars: New Estimates
• Seven temperate terrestrial planets around the nearby ultracool dwarf star TRAPPIST-1
• The California-Kepler Survey. III. A Gap in the Radius Distribution of Small Planets
• Las Cumbres Observatory Global Telescope Network
• The NextGen Model Atmosphere grid for $3000\le \Teff \le 10000\K$
• The Fourth US Naval Observatory CCD Astrograph Catalog (UCAC4)
• Kepler Presearch Data Conditioning II - A Bayesian Approach to Systematic Error Correction
• The effects of snowlines on C/O in planetary atmospheres
• The Revised TESS Input Catalog and Candidate Target List
• Efficient, uninformative sampling of limb darkening coefficients for two-parameter laws
• On the Unique Solution of Planet and Star Parameters from an Extrasolar Planet Transit Light Curve
• Kepler Presearch Data Conditioning I - Architecture and Algorithms for Error Correction in Kepler Light Curves
• Kepler planets: a tale of evaporation
• The evaporation valley in the Kepler planets
• Rotation Periods of 34,030 Kepler Main-Sequence Stars: The Full Autocorrelation Sample
• AstroImageJ: Image Processing and Photometric Extraction for Ultra-Precise Astronomical Light Curves (Expanded Edition)
• AstroImageJ: Image Processing and Photometric Extraction for Ultra-Precise Astronomical Light Curves
• Habitable Zones Around Main-Sequence Stars: Dependence on Planetary Mass
• SB9: The Ninth Catalogue of Spectroscopic Binary Orbits
• The HARPS search for southern extra-solar planets XXXI. The M-dwarf sample
• The Occurrence Rate of Small Planets around Small Stars
• Probabilistic Forecasting of the Masses and Radii of Other Worlds
• The GALAH+ Survey: Third Data Release
• 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
• The California Kepler Survey VII. Precise Planet Radii Leveraging Gaia DR2 Reveal the Stellar Mass Dependence of the Planet Radius Gap
• An asteroseismic view of the radius valley: stripped cores, not born rocky
• The Role of Core Mass in Controlling Evaporation: the Kepler Radius Distribution and the Kepler-36 Density Dichotomy
• Core-powered mass loss and the radius distribution of small exoplanets
• C/O ratio as a Dimension for Characterizing Exoplanetary Atmospheres
• Accurate, Empirical Radii and Masses of Planets and their Host Stars with Gaia Parallaxes
• Planetary Candidates Observed by Kepler. VIII. A Fully Automated Catalog With Measured Completeness and Reliability Based on Data Release 25
• Design Considerations for a Ground-based Transit Search for Habitable Planets Orbiting M dwarfs
• Sculpting the Valley in the Radius Distribution of Small Exoplanets as a by-product of Planet Formation: The Core-Powered Mass-Loss Mechanism
• The TESS Objects of Interest Catalog from the TESS Prime Mission
• The H$\alpha$ emission of nearby M dwarfs and its relation to stellar rotation
• How to Constrain Your M dwarf II: the mass-luminosity-metallicity relation from 0.075 to 0.70$M_{\odot }$
• A temperate rocky super-Earth transiting a nearby cool star
• Stellar Flares from the First Tess Data Release: Exploring a New Sample of M-dwarfs
• STARRY: Analytic Occultation Light Curves
• PandExo: A Community Tool for Transiting Exoplanet Science with JWST & HST
• Kepler Data Validation I -- Architecture, Diagnostic Tests, and Data Products for Vetting Transiting Planet Candidates
• Understanding The Effects Of Stellar Multiplicity On The Derived Planet Radii From Transit Surveys: Implications for Kepler, K2, and TESS
• Density, not radius, separates rocky and water-rich small planets orbiting M dwarf stars
• The rotation and Galactic kinematics of mid M dwarfs in the Solar Neighborhood
• Parallax Systematics and Photocenter Motions of Benchmark Eclipsing Binaries in Gaia EDR3
• A Spectroscopic Catalog of the Brightest (J<9) M Dwarfs in the Northern Sky
• Make Super-Earths, Not Jupiters: Accreting Nebular Gas onto Solid Cores at 0.1 AU and Beyond
• Real-time processing of the imaging data from the network of Las Cumbres Observatory Telescopes using BANZAI
• Kepler Data Validation II -- Transit Model Fitting and Multiple-Planet Search
• Revisited Mass-Radius relations for exoplanets below 120 Earth masses
• Wotan: Comprehensive time-series de-trending in Python
• Observing the Atmospheres of Known Temperate Earth-sized Planets with JWST
• Planetary Candidates Observed by Kepler. VII. The First Fully Uniform Catalog Based on The Entire 48 Month Dataset (Q1-Q17 DR24)
• LDTk: Limb Darkening Toolkit
• Modeling Repeated M-dwarf Flaring at an Earth-like Planet in the Habitable Zone: I. Atmospheric Effects for an Unmagnetized Planet
• An Increase in the Mass of Planetary Systems around Lower-Mass Stars
• Gaia Early Data Release 3: Summary of the contents and survey properties
• Revised metallicity classes for low-mass stars: dwarfs (dM), subdwarfs (sdM), extreme subdwarfs (esdM), and ultra subdwarfs (usdM)
• A combined transmission spectrum of the Earth-sized exoplanets TRAPPIST-1 b and c
• exoplanet: Gradient-based probabilistic inference for exoplanet data & other astronomical time series
• Eclipsing Binary Stars as Benchmarks for Trigonometric Parallaxes in the Gaia Era
• Signatures of the Core-Powered Mass-Loss Mechanism in the Exoplanet Population: Dependence on Stellar Properties and Observational Predictions
• The Solar Neighborhood XLV. The Stellar Multiplicity Rate of M Dwarfs Within 25 pc
• Prospecting in late-type dwarfs: a calibration of infrared and visible spectroscopic metallicities of late-K and M dwarfs spanning 1.5 dex
• Identification of carbon dioxide in an exoplanet atmosphere
• The Gaia-Kepler Stellar Properties Catalog. II. Planet Radius Demographics as a Function of Stellar Mass and Age
• Spectroscopy of New High Proper Motion Stars in the Northern Sky. I. New Nearby Stars, New High Velocity Stars, and an Enhanced Classification Scheme for M Dwarfs
• Empirical, Accurate Masses and Radii of Single Stars with TESS and Gaia
• Magnetism, rotation, and nonthermal emission in cool stars -- Average magnetic field measurements in 292 M dwarfs
• The Origin of RNA Precursors on Exoplanets
• Evolution of the radius valley around low mass stars from $Kepler$ and $K2$
• Vetting of 384 TESS Objects of Interest with TRICERATOPS and Statistical Validation of 12 Planet Candidates
• A nearby M star with three transiting super-Earths discovered by K2
• Habitability and Biosignatures of Hycean Worlds
• Analytic Planetary Transit Light Curves and Derivatives for Stars with Polynomial Limb Darkening
• Is Proxima Centauri b habitable? -- A study of atmospheric loss
• The CARMENES search for exoplanets around M dwarfs -- Planet occurrence rates from a subsample of 71 stars
• ELLC - a fast, flexible light curve model for detached eclipsing binary stars and transiting exoplanets
• The Factory and The Beehive II. Activity and Rotation in Praesepe and the Hyades
• The TESS-HERMES survey Data Release 1: high-resolution spectroscopy of the TESS southern continuous viewing zone
• Flare Statistics for Young Stars from a Convolutional Neural Network Analysis of $\text{TESS}$ Data
• Mass and Mass Scalings of Super-Earths
• On the Age of the TRAPPIST-1 System
• A Spectroscopic Analysis of the California-Kepler Survey Sample: I. Stellar Parameters, Planetary Radii and a Slope in the Radius Gap
• Revisiting Proxima with ESPRESSO
• UV habitable zones around M stars
• An empirical template library of stellar spectra for a wide range of spectral classes, luminosity classes, and metallicities using SDSS BOSS spectra
• SPECULOOS -- Ultracool Dwarf Transit Survey: Target List and Strategy
• The First Habitable Zone Earth-sized Planet from TESS. I: Validation of the TOI-700 System
• A super-Earth and a sub-Neptune orbiting the bright, quiet M3 dwarf TOI-1266
• MOST Observations of our Nearest Neighbor: Flares on Proxima Centauri
• UV Surface Habitability of the TRAPPIST-1 System
• The evolution of habitable zones during stellar lifetimes and its implications on the search for extraterrestrial life
• Formation and composition of planets around very low mass stars
• Masses and compositions of three small planets orbiting the nearby M dwarf L231-32 (TOI-270) and the M dwarf radius valley
• Speckle Observations of TESS Exoplanet Host Stars. II. Stellar Companions at 1-1000 AU and Implications for Small Planet Detection
• A Search for Water in the Atmosphere of HAT-P-26b Using LDSS-3C
• Planetary system LHS 1140 revisited with ESPRESSO and TESS
• Risks for life on habitable planets from superflares of their host stars
• Exploring the age dependent properties of M and L dwarfs using Gaia and SDSS
• SPIRou Input Catalog: Activity, Rotation and Magnetic Field of Cool Dwarfs
• The formation of mini-Neptunes
• Two temperate super-Earths transiting a nearby late-type M dwarf
• The Densities of Planets in Multiple Stellar Systems
• Optical Spectroscopic Classification and Membership of Young M Dwarfs in Star-Forming Regions
• prose: A Python framework for modular astronomical images processing
• The CARMENES search for exoplanets around M dwarfs - HD 147379b: A nearby Neptune in the temperate zone of an early-M dwarf
• First limits on the occurrence rate of short-period planets orbiting brown dwarfs
• WASP-23b: a transiting hot Jupiter around a K dwarf and its Rossiter-McLaughlin effect
• Habitable Zones of Post-Main Sequence Stars
• GJ 273: On the formation, dynamical evolution and habitability of a planetary system hosted by an M dwarf at 3.75 parsec
• Unresolved Binary Exoplanet Host Stars Fit as Single Stars: Effects on the Stellar Parameters
• On-sky commissioning of MAROON-X: A new precision radial velocity spectrograph for Gemini North
• Predicting the Exoplanet Yield of the TESS Prime and Extended Missions Through Years 1-7
• The Impending Opacity Challenge in Exoplanet Atmospheric Characterization
• TOI-1235 b: a keystone super-Earth for testing radius valley emergence models around early M dwarfs
• Photometry and Performance of SPECULOOS-South
• TOI-269 b: An eccentric sub-Neptune transiting a M2 dwarf revisited with ExTrA
• Formation and Detection of Earth Mass Planets around Low Mass Stars
• Possibilities for an Aerial Biosphere in Temperate Sub Neptune-Sized Exoplanet Atmospheres
• Stellar Flares versus Luminosity: XUV-induced Atmospheric Escape and Planetary Habitability
• HD 28109 hosts a trio of transiting Neptunian planets including a near-resonant pair, confirmed by ASTEP from Antarctica
• Precise mass determination for the keystone sub-Neptune planet transiting the mid-type M dwarf G 9-40
• TOI-712: a system of adolescent mini-Neptunes extending to the habitable zone

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• Water Condensation Zones around Main Sequence Stars
• The SHERLOCK pipeline: new exoplanet candidates in the WASP-16, HAT-P-27, HAT-P-26, and TOI-2411 systems
• Hundreds of TESS exoplanets might be larger than we thought
• TOI-4336 A b: A temperate sub-Neptune ripe for atmospheric characterization in a nearby triple M-dwarf system
• Planet Hunters TESS V: a planetary system around a binary star, including a mini-Neptune in the habitable zone
• MANGOS II: Five new giant planets orbiting low-mass stars
• Probing the Limits of Habitability: A Catalog of Rocky Exoplanets in the Habitable Zone
• SPECULOOS: five years hunting terrestrial planets around ultra-cool dwarfs
• TOI-7166 b: A Habitable Zone mini-Neptune planet around a nearby low-mass star
• A Cool Earth-sized Planet Candidate Transiting a Tenth Magnitude K-dwarf From K2
• TOI-4552 b: A new ultra-short period rocky world revealed by NIRPS and TESS
• Multicolour Validation of Two Temperate Mini-Neptunes Around M-dwarf Habitable Zones
• Hidden Gems in TESS: sherlock finds two new rocky planets around nearby M dwarfs
• Topography-Induced Stationary Waves and the Onset of Nightside Warming on Rocky Planets around M-dwarf Stars