THE MASS–RADIUS(–ROTATION?) RELATION FOR LOW-MASS STARS

By A. Kraus, R. Tucker, Michael Thompson, E. Craine, L. Hillenbrand. 2010

145 citations recorded by the source corpus.

The fundamental properties of low-mass stars are not as well understood as those of their more massive counterparts. The best method for constraining these properties, especially masses and radii, is to study eclipsing binary systems, but only a small number of late-type (⩾M0) systems have been identified and well characterized to date. We present the discovery and characterization of six new M dwarf eclipsing binary systems. The 12 stars in these eclipsing systems have masses spanning 0.38–0.59 M☉ and orbital periods of 0.6–1.7 days, with typical uncertainties of ∼0.3% in mass and ∼0.5%–2.0% in radius. Combined with six known systems with high-precision measurements, our results reveal an intriguing trend in the low-mass regime. For stars with M= 0.35–0.80 M☉, components in short-period binary systems (P≲1 day; 12 stars) have radii which are inflated by up to 10% (μ = 4.8% ± 1.0%) with respect to evolutionary models for low-mass main-sequence stars, whereas components in longer-period systems (>1.5 days; 12 stars) tend to have smaller radii (μ = 1.7% ± 0.7%). This trend supports the hypothesis that short-period systems are inflated by the influence of the close companion, most likely because they are tidally locked into very high rotation speeds that enhance activity and inhibit convection. In summary, very close binary systems are not representative of typical M dwarfs, but our results for longer-period systems indicate that the evolutionary models are broadly valid in the M∼ 0.35–0.80 M☉ regime.

Subfields: Astronomy and Astrophysics, Instrumentation, Statistical and Nonlinear Physics

View Paper: https://www.semanticscholar.org/paper/018ee80db2984d3528c7a68f2494acce431391ad

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Citations in the corpus

A STELLAR CENSUS OF THE TUCANA–HOROLOGIUM MOVING GROUP (2014, methodology): “This process is described in more detail in Kraus et al. (2011) and Law 8 http://www.astro.utoronto.ca/ rucinski/ 8 et al. (2012).”
Improving PARSEC models for very low mass stars (2014, background): “This mismatch in the stellar radii is very significant, and has already been noticed by a number of authors (e.g. Casagrande, Flynn & Bessell 2008; Kraus et al. 2011, and references therein).”
CHARACTERIZING THE COOL KOIs. II. THE M DWARF KOI-254 AND ITS HOT JUPITER (2011, result): “…this analysis are based on short-period eclipsing binaries, for which there is the possibility that rotation-induced magnetic and coronal activity, as well as metallicity-inhibited convection may lead to anomalously inflated radii compared to single M dwarfs (LópezMorales 2007; Kraus et al. 2011).”
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).”
MESA ISOCHRONES AND STELLAR TRACKS (MIST). I. SOLAR-SCALED MODELS (2016, background): “A proposed explanation for this mismatch invokes magnetic activity and rotation effects that are not currently modeled accurately (Spruit & Weiss 1986; Morales et al. 2008, 2010; Irwin et al. 2011; Kraus et al. 2011; Feiden & Chaboyer 2012; MacDonald & Mullan 2014; Jackson & Jeffries 2014).”
PLANETS AROUND LOW-MASS STARS (PALMS). IV. THE OUTER ARCHITECTURE OF M DWARF PLANETARY SYSTEMS (2014, background): “Targets from Shkolnik et al. (2009) have been vetted for close spectroscopic binaries with few-day periods (Shkolnik et al. 2010), which also produce activity as a result of rotationally-enhanced dynamo activity caused by tidal locking (e.g., Torres et al. 2002; Kraus et al. 2011).”
THE K2 ECLIPTIC PLANE INPUT CATALOG (EPIC) AND STELLAR CLASSIFICATIONS OF 138,600 TARGETS IN CAMPAIGNS 1–8 (2015, background): “Specifically, radii for M dwarfs at fixed Teff are systematically smaller in Padova models, which disagrees with empirical measurements from long-baseline interferometry (Boyajian et al. 2012b, 2013) or low-mass eclipsing binary systems (Kraus et al. 2011; Carter et al. 2011).”
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).”
HOW TO CONSTRAIN YOUR M DWARF: MEASURING EFFECTIVE TEMPERATURE, BOLOMETRIC LUMINOSITY, MASS, AND RADIUS (2015, background): “Studies of low-mass eclipsing binary systems (LMEBs) find that stellar models systematically underpredict stellar radii and overpredict Teff values by up to 4% (e.g., Kraus et al. 2011; Feiden & Chaboyer 2012a; Spada et al. 2013).”
The Habitability of Planets Orbiting M-dwarf Stars (2016, background): “This result is robust to other possible observational biases such as tidal inflation in binaries, though the effect is smaller when the binary is widely separated (Kraus et al., 2011; Irwin et al., 2011).”
The Formation and Early Evolution of Low-Mass Stars and Brown Dwarfs (2012, background): “…of wide binaries and their average separation decrease steadily from solar-mass stars to brown dwarfs (Konopacky et al. 2007; Kraus & Hillenbrand 2007, 2009a, 2012; Kraus et al. 2011b; Kraus, White & Hillenbrand 2006; Lafrenière et al. 2008; Neuhäuser et al. 2002, K. Todorov, in preparation).”
The star formation history and accretion-disc fraction among the K-type members of the Scorpius–Centaurus OB association (2016, background): “The most obvious reason is that evolutionary models have difficulty predicting the radii of main-sequence M-type stars, systematically underestimating their radii by ∼5- 20% (Torres & Ribas 2002; Boyajian et al. 2012; see also Kraus et al. 2011).”
Homogeneous studies of transiting extrasolar planets – IV. Thirty systems with space-based light curves (2011, background): “The final sample contains 90 dEBs (180 stars), and benefits in particular from the six new low-mass dEBs studied by Kraus et al. (2011).”
REVISED STELLAR PROPERTIES OF KEPLER TARGETS FOR THE QUARTER 1–16 TRANSIT DETECTION RUN (2013, background): “…of low-mass dwarfs with empirically measured radii, masses and effective temperatures from longbaseline interferometry (Boyajian et al. 2012, 2013) or low-mass eclipsing binary systems (Kraus et al. 2011; Carter et al. 2011) (although significant offsets still exist, see Boyajian et al. 2013).”
CHARACTERIZING THE COOL KOIs. III. KOI 961: A SMALL STAR WITH LARGE PROPER MOTION AND THREE SMALL PLANETS (2012, result): “…been suggested that mutual magnetic interactions in short-period M dwarf binaries introduce discrepancies in the mass-radius-effective temperature relationships as compared to single field M dwarfs (Chabrier et al. 2007), and recent observational evidence supports this scenario (Kraus et al. 2011).”
STELLAR DIAMETERS AND TEMPERATURES. II. MAIN-SEQUENCE K- AND M-STARS (2012, background): “Other contributing factors to the EB radii offsets with respect to models such as the orbital period and the rotation rate have been considered and refuted (Kraus et al. 2011; Irwin et al. 2011).”