On the Correlation between the Magnetic Activity Levels, Metallicities, and Radii of Low-Mass Stars

By Mercedes López-Morales. 2007

251 citations recorded by the source corpus.

The recent increase in the number of radius measurements of very low mass stars from eclipsing binaries and interferometry of single stars has raised more questions about what could be causing the discrepancy between the observed radii and those predicted by models. The two main explanations being proposed are a correlation between the radii of the stars and either their activity levels or their metallicities. This paper presents a study of such correlations using all the data published to date. The study also investigates correlations between the radius deviations from the models and the masses of the stars. There is no clear correlation between activity level and radius for the single stars in the sample. These single stars are slow rotators, with typical velocities vrot sin i < 3.0 km s-1. A clear correlation however exists in the case of the faster rotating members of binaries. This result is based on the X-ray emission levels of the stars. There also appears to be an increase in the deviation of the radii of single stars from the models as a function of metallicity, as previously indicated by Berger et al. The stars in binaries do not seem to follow the same trend. Finally, the Baraffe et al. models reproduce well the radius observations below 0.30-0.35 M☉, where the stars become fully convective, although this result is preliminary since almost all the sample stars in that mass range are slow rotators and metallicities have not been measured for most of them. The results indicate that stellar activity and metallicity play an important role in determining the radius of very low mass stars, at least above 0.35 M☉.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/cef1956e57e470320618ff44c4dddc503c9b610c

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Citations in the corpus

Disentangling the Planet from the Star in Late-Type M Dwarfs: A Case Study of TRAPPIST-1g (2018, background): “This factor can be viewed as the correction from the literature stellar radius to the implicit model radius; it is well known that there are issues with theoretical models underestimating the radii of low mass stars (e.g., López-Morales 2007; Boyajian et al. 2012).”
Accurate masses and radii of normal stars: modern results and applications (2009, background): “Metallicity has been discussed as an additional cause (Berger et al. 2006; López-Morales 2007), but would not be expected to affect fast and slow rotators differently.”
Homogeneous studies of transiting extrasolar planets – IV. Thirty systems with space-based light curves (2011, background): “This arose because the known well-studied dEBs tend to have substantially larger radii than predictedby the models (see e.g. López-Morales 2007; Ribas et al. 2008), soa m re massive star was needed to reproduce the density obtained from Figure 3.”
Confirmation of the Electron Cyclotron Maser Instability as the Dominant Source of Radio Emission from Very Low Mass Stars and Brown Dwarfs (2008, background): “…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 2007; Morales et al. 2008) or metallicity (Berger et al. 2006).”
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): “…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 et al. 2011).”
M dwarfs: effective temperatures, radii and metallicities (2008, background): “…explanations would be the analysis of late K and early M dwarfs’ spectra as well as to run the MOITE for a large sample of (magnetically) active M dwarfs, to help in searching for correlation between the radius discrepancy and activity level or other physical parameters (e.g. López-Morales 2007).”
PROSPECTING IN LATE-TYPE DWARFS: A CALIBRATION OF INFRARED AND VISIBLE SPECTROSCOPIC METALLICITIES OF LATE K AND M DWARFS SPANNING 1.5 dex (2012, background): “However, none of our most metal-poor companions show H-α emission, whereas radius inflation in tight binaries is usually associated with high chromospheric activity (López-Morales 2007; Kraus et al. 2011; Stassun et al. 2012).”
THE MASS–RADIUS(–ROTATION?) RELATION FOR LOW-MASS STARS (2010, background): “However, one or both components for our other two systems sit significantly above the model sequence, as do most measurements obtained in previous studies; this trend has been well-known for several years (e.g. Lopez-Morales 2007).”
STELLAR DIAMETERS AND TEMPERATURES. II. MAIN-SEQUENCE K- AND M-STARS (2012, methodology): “Based on the normalized X-ray emission LX/LBOL results from Table 6, and Column 5 in Table 1 from López-Morales (2007), the stars in binaries are 102–103 times more active than the single star counterparts.”
THE EVOLUTION OF CATACLYSMIC VARIABLES AS REVEALED BY THEIR DONOR STARS (2011, methodology): “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.”
A PHOTOMETRIC VARIABILITY SURVEY OF FIELD K AND M DWARF STARS WITH HATNet (2009, unknown): “(Ribas 2006; Torres et al. 2006; López-Morales 2007; Chabrier et al. 2007).”
The Habitability of Planets Orbiting M-dwarf Stars (2016, background): “There exists a tension between stellar models and empirically-derived properties for low-mass stars at the level of 5-10% (Torres & Ribas, 2002; López-Morales, 2007; Morales et al., 2008, 2009; Vida et al., 2009; Carter et al., 2011; Kraus et al., 2011).”
NEAR-INFRARED METALLICITIES, RADIAL VELOCITIES, AND SPECTRAL TYPES FOR 447 NEARBY M DWARFS (2013, background): “They find the radii to be inflated by 4% relative to theoretical predictions, reflecting a well-known problem with stellar models at the bottom of the main sequence (e.g. Lopez-Morales 2007; Boyajian et al. 2012).”
Homogeneous studies of transiting extrasolar planets – I. Light-curve analyses (2008, background): “…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 components of…”