Masses and Radii of Low-Mass Stars: Theory Versus Observations

By I. Ribas. 2005

142 citations recorded by the source corpus.

Eclipsing binaries with M-type components are still rare objects. Strong observational biases have made that today only a few eclipsing binaries with component masses below 0.6 M⊙ and well-determined fundamental properties are known. However, even in these small numbers the detailed comparison of the observed masses and radii with theoretical predictions has revealed large disagreements. Current models seem to predict radii of stars in the 0.4--0.8 M⊙ range to be some 5--15% smaller than observed. Given the high accuracy of the empirical measurements (a few percent in both mass and radius), these differences are highly significant. I review all the observational evidence on the properties of M-type stars and discuss a possible scenario based on stellar activity to explain the observed discrepancies.

Subfields: Astronomy and Astrophysics, Education, Instrumentation

View Paper: https://www.semanticscholar.org/paper/af64a99a94b5a2656c01d44bb3d8345d3e18a335

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Citations in the corpus

CHARACTERIZING THE COOL KOIs. II. THE M DWARF KOI-254 AND ITS HOT JUPITER (2011, methodology): “, which gives a polynomial relationship that is very similar to the one used by J11 based on the eclipsing binaries in the Ribas (2006) sample.”
Spitzer Transit and Secondary Eclipse Photometry of GJ 436b (2007, methodology): “33R ∼ M the fitting procedure with the empirical mass-radius relation (Ribas 2006) to find the best stellar mass and radius,R p M and planet radius, at each impact parameter.”
A PHOTOMETRIC VARIABILITY SURVEY OF FIELD K AND M DWARF STARS WITH HATNet (2009, background): “…K and M dwarf components have led to the realization that the radii of early-M dwarfs and late-K dwarfs are somewhat larger than predicted by theory (the number typically stated is 10%; Torres & Ribas 2002; Ribas 2003; López-Morales 2005; Ribas 2006; Beatty et al. 2007; Fernandez et al. 2009).”
Detection of carbon monoxide in the high-resolution day-side spectrum of the exoplanet HD 189733b (2013, background): “Precise dynamical measurements of the masses and radii of low-mass stars in DLEBs are not well-reproduced by stellar evolutions models and have radii that are up to 15% larger than predicted (López-Morales & Ribas 2005; Ribas 2006).”
Confirmation of the Electron Cyclotron Maser Instability as the Dominant Source of Radio Emission from Very Low Mass Stars and Brown Dwarfs (2008, background): “…and those directly measured, either through observations of eclipsing binary systems or interferometric studies of single stars, has been reported (Ribas 2006, and references therein), possibly due to the effects of activity (Mullan & McDonald 2001; López-Morales & Ribas 2005; López-Morales…”
CHARACTERIZING THE COOL KOIs. III. KOI 961: A SMALL STAR WITH LARGE PROPER MOTION AND THREE SMALL PLANETS (2012, background): “However, empirical measurements of low-mass stellar parameters and predictions from evolutionary isochrones show significant discrepancies, particularly with regard to stellar radius and effective temperature (Ribas 2006; Torres 2011).”
AN EMPIRICAL CALIBRATION TO ESTIMATE COOL DWARF FUNDAMENTAL PARAMETERS FROM H-BAND SPECTRA (2014, background): “Additionally, if magnetic activity is responsible for the inflated radii, as discussed in Lopez Morales & Ribas (2005), Ribas (2006), Lopez Morales (2007), and Chabrier et al. (2007), a mass-radius-activity relationship would be required to accurately determine the radii of field dwarfs.”
M dwarfs: effective temperatures, radii and metallicities (2008, result): “In panels (a) and (b) of Figure 13 it is obvious that current models underestimate the radii of the M dwarfs by 15 − 20 percent, as already noticed by several other authors (see Ribas 2006 for a review).”
Large-scale magnetic topologies of late M dwarfs⋆ (2008, result): “This is consistent with the findings of Ribas (2006) on eclipsing binaries, further confirmed on a sample of single late-K and M dwarfs by Morales et al. (2008), that active low-mass stars exhibit significantly larger radii and cooler Teff than inactive stars of similar masses.”
THE EVOLUTION OF CATACLYSMIC VARIABLES AS REVEALED BY THEIR DONOR STARS (2011, result): “A hint along these lines had first been noted by Ribas (2006) and López-Morales (2007), but our larger database here allows us to confirm and quantify this impression.”
Large-scale magnetic topologies of late M dwarfs★: Magnetic topologies of late M dwarfs (2010, result): “The accuracy of these models for active M dwarfs is a debated subject (e.g., Ribas 2006), but recent studies indicate that the agreement with observations is very good for late M dwarfs (Demory et al. 2009).”
METALLICITY AND TEMPERATURE INDICATORS IN M DWARF K-BAND SPECTRA: TESTING NEW AND UPDATED CALIBRATIONS WITH OBSERVATIONS OF 133 SOLAR NEIGHBORHOOD M DWARFS (2011, background): “…binaries reveal systematic offsets in inferred temperatures and radii that correlate with both orbital period and tracers of magnetic activity (Ribas 2006; López-Morales 2007), suggesting that more wide binaries are needed to accurately infer the parameters typical isolated M dwarfs (Kraus…”
Design Considerations for a Ground-Based Transit Search for Habitable Planets Orbiting M Dwarfs (2007, methodology): “The first method is problematic in that the theoretical models (not just those of Baraffe et al. 1998) are known to underestimate radii by 5–15% for stars in the range 0:4 M⊙ ≲M ≲ 0:8 M⊙ (Ribas 2006).”
Homogeneous studies of transiting extrasolar planets – I. Light-curve analyses (2008, background): “…by approximately 10% over that predicted by the models, an anomaly which has previously been noticed for low-mass stars in eclipsing binary systems (Ribas 2003, 2006; López-Morales 2007), single low-mass field stars studied using interferometry (Berger et al. 2006), and the low-mass secondary…”
On the Correlation between the Magnetic Activity Levels, Metallicities, and Radii of Low-Mass Stars (2007, background): “The first suggests that the discrepancies between models and observations are caused by differences in the level of activity of the stars (López-Morales & Ribas 2005; Ribas 2006).”
ON THE ANGULAR MOMENTUM EVOLUTION OF FULLY CONVECTIVE STARS: ROTATION PERIODS FOR FIELD M-DWARFS FROM THE MEarth TRANSIT SURVEY (2010, methodology): “…for the target star sufficient to detect a 2 R⊕ planet transit at 3σ per data point, for the assumed stellar radius, which is based on the Delfosse et al. (2000) K-band massabsolute magnitude relation, and a polynomial fit to the empirical mass-radius data of Ribas (2006) to convert mass to radius.”
Large-scale magnetic topologies of early M dwarfs (2008, result): “Our results therefore independently confirm the report that cool low-mass active stars, either single (Morales et al. 2008) or within close eclipsing binaries (Ribas 2006), usually have oversized radii with respect to inactive stars of similar spectral types.”