A discontinuity in the $T_{\mathrm{eff}}$-radius relation of M-dwarfs

Abstract

We report on 13 new high-precision measurements of stellar diameters for low-mass dwarfs obtained by means of near-infrared long-baseline interferometry with PIONIER at the Very Large Telescope Interferometer. Together with accurate parallaxes from Gaia DR2, these measurements provide precise estimates for their linear radii, effective temperatures, masses, and luminosities. This allows us to refine the effective temperature scale, in particular towards the coolest M-dwarfs. We measure for late-type stars with enhanced metallicity slightly inflated radii, whereas for stars with decreased metallicity we measure smaller radii. We further show that Gaia DR2 effective temperatures for M-dwarfs are underestimated by $\sim$ 8.2 % and give an empirical $M_G$-$T_{\mathrm{eff}}$ relation which is better suited for M-dwarfs with $T_{\mathrm{eff}}$ between 2600 and 4000 K. Most importantly, we are able to observationally identify a discontinuity in the $T_{\mathrm{eff}}$-radius plane, which is likely due to the transition from partially convective M-dwarfs to the fully convective regime. We found this transition to happen between 3200 K and 3340 K, or equivalently for stars with masses $\approx 0.23M_{\odot }$. We find that in this transition region the stellar radii are in the range from 0.18 to 0.42$R_{\odot }$ for similar stellar effective temperatures.

arXiv comment11 pages, 9 figures, accepted in MNRAS

References in corpus (35)

• Gaia Data Release 2. Summary of the contents and survey properties
• The Transiting Exoplanet Survey Satellite
• A new extensive library of PHOENIX stellar atmospheres and synthetic spectra
• Multimodal nested sampling: an efficient and robust alternative to MCMC methods for astronomical data analysis
• X-ray spectral modelling of the AGN obscuring region in the CDFS: Bayesian model selection and catalogue
• How to Constrain Your M Dwarf: measuring effective temperature, bolometric luminosity, mass, and radius
• The HARPS search for southern extra-solar planets XXXI. The M-dwarf sample
• The Occurrence Rate of Small Planets around Small Stars
• Stellar Diameters and Temperatures II. Main Sequence K & M Stars
• Theory of Low-Mass Stars and Substellar Objects
• Gaia Data Release 2: first stellar parameters from Apsis
• Possible Solutions to the Radius Anomalies of Transiting Giant Planets
• PIONIER: a 4-telescope visitor instrument at VLTI
• Simulations of dynamo action in fully convective stars
• Large-scale magnetic topologies of early M dwarfs
• The rotation and Galactic kinematics of mid M dwarfs in the Solar Neighborhood
• A revised estimate of the occurrence rate of terrestrial planets in the habitable zones around kepler m-dwarfs
• Limb darkening and exoplanets: testing stellar model atmospheres and identifying biases in transit parameters
• On the angular momentum evolution of fully-convective stars: rotation periods for field M-dwarfs from the MEarth transit survey
• The Solar Neighborhood XXXVII: The Mass-Luminosity Relation for Main Sequence M Dwarfs
• Solar-type dynamo behaviour in fully convective stars without a tachocline
• First radius measurements of very low mass stars with the VLTI
• Mass-radius relation of low and very low-mass stars revisited with the VLTI
• First Results from the CHARA Array. IV. The Interferometric Radii of Low-Mass Stars
• Stellar Diameters and Temperatures V. Eleven Newly Characterized Exoplanet Host Stars
• Astrophysical Parameters and Habitable Zone of the Exoplanet Hosting Star GJ 581
• The GJ 436 System: Directly Determined Astrophysical Parameters of an M-Dwarf and Implications for the Transiting Hot Neptune
• Metallicity of M dwarfs IV. A high-precision [Fe/H] and Teff technique from high-resolution optical spectra for M dwarfs
• Revised Filter Profiles and Zero Points for Broadband Photometry
• Magnetic Inflation and Stellar Mass II: On the Radii of Single, Rapidly Rotating, Fully Convective M Dwarf Stars
• A Gap in the Lower Main Sequence Revealed by Gaia Data Release 2
• Establishing Visible Interferometer System Responses: Resolved and Unresolved Calibrators
• A He3 driven instability near the fully convective boundary
• Fundamental properties of red-clump stars from long-baseline H-band interferometry
• An explanation for the gap in the Gaia HRD for M dwarfs

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