The CARMENES search for exoplanets around M dwarfs. Occurrence rates of Earth-like planets around very low-mass stars

Abstract

Aims: Previous estimates of planet occurrence rates in the CARMENES survey indicated increased numbers of planets on short orbits for M dwarfs with masses below 0.34\,M${}_{\odot }$. Here we focused on the lowest-mass stars in the survey, comprising 15 inactive targets with masses under 0.16\,M${}_{\odot }$. Methods: To correct for detection biases, we determined detection sensitivity maps for individual targets and the entire sample. Using Monte Carlo simulations, we estimated planet occurrence rates for orbital periods of 1\,d to 100\,d and minimum masses from 0.5\,M${}_{\oplus }$ to 10\,M${}_{\oplus }$. Results: The radial velocity (RV) data from CARMENES reveal four new planets around three stars in our sample, namely G~268--110\,b, G~261--6\,b, and G~192--15\,b and c. All three b planets have minimum masses of 1.03--1.52\,M${}_{\oplus }$ and orbital periods of 1.43--5.45\,d, while G~192--15\,c is a 14.3\,M${}_{\oplus }$ planet on a wide, eccentric orbit with $P\approx 1218$\,d and $e\approx 0.68$. Our occurrence rates suggest considerable dependencies with respect to stellar masses. For planets below 3\,M${}_{\oplus }$ we found rates consistent with one planet per star across all investigated periods, but the rates decrease almost by an order of magnitude for larger planet masses up to 10\,M${}_{\oplus }$. Compared to previous studies, low-mass stars tend to harbor more planets with $P<10$\,d. We also demonstrate that synthetic planet populations based on the standard core accretion scenario predict slightly more massive planets on wider orbits than observed. Conclusions: Our findings confirm that planet occurrence rates vary with stellar masses even among M dwarfs, as we found more planets with lower masses and on shorter orbits in our subsample of very low-mass stars compared to more massive M dwarfs. Therefore, we emphasize the need for additional differentiation in future studies.

arXiv commentNumber of pages: 25; number of figures: 23 (12 in main + 11 in appendix). Accepted in A&A; DOI (pending): 10.1051/0004-6361/202453381 (Volume 696, Article number A101)

References in corpus (79)

• The Transiting Exoplanet Survey Satellite
• Bayes in the sky: Bayesian inference and model selection in cosmology
• Planet Occurrence within 0.25 AU of Solar-type Stars from Kepler
• Giant Planet Occurrence in the Stellar Mass-Metallicity Plane
• The HARPS search for southern extra-solar planets XXXI. The M-dwarf sample
• Northern Sky Variability Survey (NSVS): Public data release
• Spectrum radial velocity analyser (SERVAL). High-precision radial velocities and two alternative spectral indicators
• The Lick Planet Search: Detectability and Mass Thresholds
• Juliet: a versatile modelling tool for transiting and non-transiting exoplanetary systems
• A Re-appraisal of the Habitability of Planets Around M Dwarf Stars
• Gaia Early Data Release 3: The Gaia Catalogue of Nearby Stars
• Radial velocity planets de-aliased. A new, short period for Super-Earth 55 Cnc e
• The VLA/ALMA Nascent Disk and Multiplicity (VANDAM) Survey of Orion Protostars. A Statistical Characterization of Class 0 and I Protostellar Disks
• Density, not radius, separates rocky and water-rich small planets orbiting M dwarf stars
• Planetesimal formation starts at the snow line
• The rotation and Galactic kinematics of mid M dwarfs in the Solar Neighborhood
• On the angular momentum evolution of fully-convective stars: rotation periods for field M-dwarfs from the MEarth transit survey
• Exploring The Frequency Of Close-In Jovian Planets Around M Dwarfs
• Detectability of Extrasolar Planets in Radial Velocity Surveys
• 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
• The New Generation Planetary Population Synthesis (NGPPS). I. Bern global model of planet formation and evolution, model tests, and emerging planetary systems
• Characterizing the Cool KOIs II. The M Dwarf KOI-254 and its Hot Jupiter
• Bayesian search for low-mass planets around nearby M dwarfs. Estimates for occurrence rate based on global detectability statistics
• Kepler Planet Occurrence Rates for Mid-Type M Dwarfs as a Function of Spectral Type
• The VLA Nascent Disk And Multiplicity Survey of Perseus Protostars (VANDAM). IV. Free-Free Emission from Protostars: Links to Infrared Properties, Outflow Tracers, and Protostellar Disk Masses
• Born Dry in the Photo-Evaporation Desert: Kepler's Ultra-Short-Period Planets Formed Water-Poor
• CARMENES input catalogue of M dwarfs V. Luminosities, colours, and spectral energy distributions
• The CARMENES search for exoplanets around M dwarfs -- Planet occurrence rates from a subsample of 71 stars
• The CARMENES search for exoplanets around M dwarfs. First visual-channel radial-velocity measurements and orbital parameter updates of seven M-dwarf planetary systems
• The CARMENES search for exoplanets around M dwarfs. Two temperate Earth-mass planet candidates around Teegarden's Star
• The 10 parsec sample in the Gaia era
• HATS-6b: A Warm Saturn Transiting an Early M Dwarf Star, and a Set of Empirical Relations for Characterizing K and M Dwarf Planet Hosts
• The M dwarf planet search programme at the ESO VLT + UVES. A search for terrestrial planets in the habitable zone of M dwarfs
• A giant exoplanet orbiting a very low-mass star challenges planet formation models
• Super-Earth masses sculpted by pebble isolation around stars of different masses
• Correcting HIRES radial velocities for small systematic errors
• New rotation period measurements for M dwarfs in the southern hemisphere: an abundance of slowly rotating, fully convective stars
• CARMENES input catalogue of M dwarfs IV. New rotation periods from photometric time series
• The CARMENES search for exoplanets around M dwarfs. Activity indicators at visible and near-infrared wavelengths
• Detecting extrasolar planets from stellar radial velocities using Bayesian evidence
• The Origin of Planetary System Architectures. I. Multiple Planet Traps in Gaseous Discs
• Stacked Bayesian general Lomb-Scargle periodogram: Identifying stellar activity signals
• The Ophiuchus DIsk Survey Employing ALMA (ODISEA): Disk Dust Mass Distributions across Protostellar Evolutionary Classes
• The CARMENES search for exoplanets around M dwarfs. Guaranteed time observations Data Release 1 (2016-2020)
• Bayesian Re-analysis of the Gliese 581 Exoplanet System
• The CARMENES search for exoplanets around M dwarfs. Radial velocities and activity indicators from cross-correlation functions with weighted binary masks
• Evidence for 9 planets in the HD 10180 system
• Occurrence rate of hot Jupiters around early-type M dwarfs based on TESS data
• Planetesimal Population Synthesis: Pebble Flux Regulated Planetesimal Formation
• The runaway greenhouse radius inflation effect - An observational diagnostic to probe water on Earth-size planets and test the Habitable Zone concept
• The HARPS search for southern extra-solar planets. XXXIV. A planetary system around the nearby M dwarf GJ163, with a super-Earth possibly in the habitable zone
• A nearby transiting rocky exoplanet that is suitable for atmospheric investigation
• The HARPS search for southern extra-solar planets XLII. A system of Earth-mass planets around the nearby M dwarf YZ Ceti
• RV-detected planets around M dwarfs: Challenges for core accretion models
• A fading radius valley towards M-dwarfs, a persistent density valley across stellar types
• Bias and robustness of eccentricity estimates from radial velocity data
• The New Generation Planetary Population Synthesis (NGPPS). V. Predetermination of planet types in global core accretion models
• The CARMENES search for exoplanets around M dwarfs. Measuring precise radial velocities in the near infrared: the example of the super-Earth CD Cet b
• HADES RV Programme with HARPS-N at TNG XV. Planetary occurrence rates around early-M dwarfs
• Pebbles versus planetesimals: the outcomes of population synthesis models
• Precise radial velocities of giant stars XVI. Planet occurrence rates from the combined analysis of the Lick, EXPRESS, and PPPS giant star surveys
• Comparison of different exoplanet mass detection limit methods using a sample of main-sequence intermediate-type stars
• Two temperate Earth-mass planets orbiting the nearby star GJ1002
• The CARMENES search for exoplanets around M dwarfs. Mapping stellar activity indicators across the M dwarf domain
• Galactic Kinematics and Observed Flare Rates of a Volume-Complete Sample of Mid-to-Late M-dwarfs: Constraints on the History of the Stellar Radiation Environment of Planets Orbiting Low-mass Stars
• The CARMENES search for exoplanets around M dwarfs. Characterization of the nearby ultra-compact multiplanetary system YZ Ceti
• Pan-Planets: Searching for hot Jupiters around cool dwarfs
• Realistic On-the-fly Outcomes of Planetary Collisions II: Bringing Machine Learning to N-body Simulations
• The SPIRou Legacy Survey Rotation period of quiet M dwarfs from circular polarization in near-infrared spectral lines: I. The SPIRou APERO analysis
• The MEarth project: searching for transiting habitable super-Earths around nearby M-dwarfs
• The HD 260655 system: Two rocky worlds transiting a bright M dwarf at 10 pc
• Planetary Population Synthesis and the Emergence of Four Classes of Planetary System Architectures
• The CARMENES search for exoplanets around M dwarfs, Wolf 1069 b: Earth-mass planet in the habitable zone of a nearby, very low-mass star
• Bioverse: The Habitable Zone Inner Edge Discontinuity as an Imprint of Runaway Greenhouse Climates on Exoplanet Demographics
• Discovery and mass measurement of the hot, transiting, Earth-sized planet GJ 3929 b
• The CARMENES search for exoplanets around M dwarfs. Telluric absorption corrected high S/N optical and near-infrared template spectra of 382 M dwarf stars
• Gliese 12 b: A temperate Earth-sized planet at 12 pc ideal for atmospheric transmission spectroscopy
• Active Stars in the Spectroscopic Survey of Mid-to-Late M Dwarfs Within 15pc