A discontinuity in the<i>T</i>eff–radius relation of M-dwarfs

Rabus, M.; Lachaume, R.; Jordán, Andrés; Brahm, R.; Boyajian, Tabetha S.; Braun, Kaspar von; Espinoza, N.; Berger, J.‐P.; Bouquin, J.-B. Le; Absil, Olivier

doi:10.1093/mnras/sty3430

Cited by 59 publications

(66 citation statements)

References 44 publications

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“…b Only a partial transit was observed based on a larger grid of interferometric radii yielded consistent results (Rabus et al 2019). Uncertainties in M * and R * account for both measurement errors (in K S and parallax) and uncertainties in the calibrations.…”

Section: Timing Correctionsmentioning

confidence: 77%

Zodiacal Exoplanets in Time (ZEIT). IX. A Flat Transmission Spectrum and a Highly Eccentric Orbit for the Young Neptune K2-25b as Revealed by Spitzer

Thao

Mann

Johnson

et al. 2020

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Transiting planets in nearby young clusters offer the opportunity to study the atmospheres and dynamics of planets during their formative years. To this end, we focused on K2-25b -a close-in (P =3.48 days), Neptune-sized exoplanet orbiting a M4.5 dwarf in the 650 Myr Hyades cluster. We combined photometric observations of K2-25 covering a total of 44 transits and spanning > 2 yr, drawn from a mix of space-based telescopes (Spitzer Space Telescope and K2 ) and ground-based facilities (Las Cumbres Observatory Global Telescope network and MEarth). The transit photometry spanned 0.6-4.5µm, which enabled our study of K2-25b's transmission spectrum. We combined and fit each dataset at a common wavelength within a Markov Chain Monte Carlo framework, yielding consistent planet parameters. The resulting transit depths ruled out a solar-composition atmosphere for K2-25b for the range of expected planetary masses and equilibrium temperature at a > 4σ confidence level, and are consistent with a flat transmission spectrum. Mass constraints and transit observations at a finer grid of wavelengths (e.g., from the Hubble Space Telescope) are needed to make more definitive statements about the presence of clouds or an atmosphere of high mean molecular weight. Our precise measurements of K2-25b's transit duration also enabled new constraints on the eccentricity of K2-25's orbit. We find K2-25b's orbit to be eccentric (e > 0.20) for all reasonable stellar densities and independent of the observation wavelength or instrument. The high eccentricity is suggestive of a complex dynamical history and motivates future searches for additional planets or stellar companions.

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Section: Timing Correctionsmentioning

confidence: 77%

Zodiacal Exoplanets in Time (ZEIT). IX. A Flat Transmission Spectrum and a Highly Eccentric Orbit for the Young Neptune K2-25b as Revealed by Spitzer

Thao

Mann

Johnson

et al. 2020

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“…Number of stars that would be detectable, either assuming a maximum exposure time with no noise floor or assuming that the stochastic noise floor is limited to a 1-sigma noise envelope of 1 ppm, 3 ppm, or 5 ppm. Rabus et al (2019) underestimates temperature for Proxima Centauri. We override the temperature with 3000 K, an approximation from Boyajian et al (2012).…”

Section: Comparison With Previous Workmentioning

confidence: 95%

“…However, Muirhead et al (2018) do not apply this relation to stars with T eff 2700K because the calibration sample used in Mann et al (2015) does not include stars in this low-temperature regime. Therefore certain stars in the CDC do not have an assigned temperature, and thus did not survive our initial stellar effective temperature cut of 2600 K < T eff < 4500 K. Because M dwarfs in this low-temperature regime (such as TRAPPIST-1) are of great interest to the community, we estimate the stellar temperatures for these stars ourselves using the discontinuous T eff -radius relation from Rabus et al (2019). Rabus et al (2019) use high-precision interferometry measurements of M dwarfs to derive two separate empirical relations between T eff and radius for stars with masses M < 0.23 M and M ≥ 0.23 M respectively.…”

Section: Selecting Tess Targetsmentioning

confidence: 99%

“…Therefore certain stars in the CDC do not have an assigned temperature, and thus did not survive our initial stellar effective temperature cut of 2600 K < T eff < 4500 K. Because M dwarfs in this low-temperature regime (such as TRAPPIST-1) are of great interest to the community, we estimate the stellar temperatures for these stars ourselves using the discontinuous T eff -radius relation from Rabus et al (2019). Rabus et al (2019) use high-precision interferometry measurements of M dwarfs to derive two separate empirical relations between T eff and radius for stars with masses M < 0.23 M and M ≥ 0.23 M respectively. For stars without T eff but with R < 0.5 R and K mag < 11, we implement these relations to estimate effective temperatures.…”

Section: Selecting Tess Targetsmentioning

confidence: 99%

“…List of the targets from the TESS Input Catalog that are detectable with a 3 ppm noise floor using JWST, ranked by lowest exposure time. The stellar parameters are taken from the TIC when available, and calculated using relations fromRabus et al (2019) when values are missing from the TIC. Note that many of these stars do not have temperatures in the TIC.…”

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confidence: 99%

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Dim Prospects for Transmission Spectra of Ocean Earths around M Stars

Suissa

Mandell

Wolf

et al. 2020

ApJ

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The search for water-rich Earth-sized exoplanets around low-mass stars is rapidly gaining attention because they represent the best opportunity to characterize habitable planets in the near future. Understanding the atmospheres of these planets and determining the optimal strategy for characterizing them through transmission spectroscopy with our upcoming instrumentation is essential in order to constrain their environments. For this study, we present simulated transmission spectra of tidally locked Earth-sized ocean-covered planets around late-M to mid-K stellar spectral types, utilizing GCM modeling results previously published by Kopparapu et al. (2017) as inputs for our radiative transfer calculations performed using NASA's Planetary Spectrum Generator (psg.gsfc.nasa.gov; Villanueva et al. (2018)). We identify trends in the depth of H 2 O spectral features as a function of planet surface temperature and rotation rate. These trends allow us to calculate the exposure times necessary to detect water vapor in the atmospheres of aquaplanets through transmission spectroscopy with the upcoming James Webb Space Telescope (JWST) as well as several future flagship space telescope concepts under consideration (LUVOIR and OST) for a target list constructed from the TESS Input Catalog (TIC). Our calculations reveal that transmission spectra for water-rich Earth-sized planets around low-mass stars will be dominated by clouds, with spectral features < 20 ppm, and only a small subset of TIC stars would allow for the characterization of an ocean planet in the Habitable Zone. We thus present a careful prioritization of targets that are most amenable to follow-up characterizations with next-generation instrumentation, in order to assist the community in efficiently utilizing precious telescope time.

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The EBLM project

Gill

Maxted

Evans

et al. 2019

A&A

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Some M-dwarfs around F-/G-type stars have been measured to be hotter and larger than predicted by stellar evolution models. Inconsistencies between observations and models need to be addressed with more mass, radius, and luminosity measurements of low-mass stars to test and refine evolutionary models. Our aim is to measure the masses, radii and ages of the stars in five low-mass eclipsing binary systems discovered by the WASP survey. We used WASP photometry to establish eclipse-time ephemerides and to obtain initial estimates for the transit depth and width. Radial velocity measurements were simultaneously fitted with follow-up photometry to find the best-fitting orbital solution. This solution was combined with measurements of atmospheric parameters to interpolate evolutionary models and estimate the mass of the primary star, and the mass and radius of the M-dwarf companion. We assess how the best fitting orbital solution changes if an alternative limb-darkening law is used and quantify the systematic effects of unresolved companions. We also gauge how the best-fitting evolutionary model changes if different values are used for the mixing length parameter and helium enhancement. We report the mass and radius of five M-dwarfs and find little evidence of inflation with respect to evolutionary models. The primary stars in two systems are near the “blue hook” stage of their post sequence evolution, resulting in two possible solutions for mass and age. We find that choices in helium enhancement and mixing-length parameter can introduce an additional 3−5% uncertainty in measured M-dwarf mass. Unresolved companions can introduce an additional 3−8% uncertainty in the radius of an M-dwarf, while the choice of limb-darkening law can introduce up to an additional 2% uncertainty. The choices in orbital fitting and evolutionary models can introduce significant uncertainties in measurements of physical properties of such systems.

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A discontinuity in theTeff–radius relation of M-dwarfs

Cited by 59 publications

References 44 publications

Zodiacal Exoplanets in Time (ZEIT). IX. A Flat Transmission Spectrum and a Highly Eccentric Orbit for the Young Neptune K2-25b as Revealed by Spitzer

Zodiacal Exoplanets in Time (ZEIT). IX. A Flat Transmission Spectrum and a Highly Eccentric Orbit for the Young Neptune K2-25b as Revealed by Spitzer

Dim Prospects for Transmission Spectra of Ocean Earths around M Stars

The EBLM project

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