STELLAR DIAMETERS AND TEMPERATURES. II. MAIN-SEQUENCE K- AND M-STARS

By T. Boyajian, K. von Braun, G. V. van Belle, H. Mcalister, T. T. ten Brummelaar, S. Kane, P. Muirhead, Jeremy Jones, Russel J. White, G. Schaefer and 14 more. 2012

586 citations recorded by the source corpus.

We present interferometric angular diameter measurements of 21 low-mass, K- and M-dwarfs made with the CHARA Array. This sample is enhanced by adding a collection of radius measurements published in the literature to form a total data set of 33 K–M-dwarfs with diameters measured to better than 5%. We use these data in combination with the Hipparcos parallax and new measurements of the star's bolometric flux to compute absolute luminosities, linear radii, and effective temperatures for the stars. We develop empirical relations for ∼K0 to M4 main-sequence stars that link the stellar temperature, radius, and luminosity to the observed (B − V), (V − R), (V − I), (V − J), (V − H), and (V − K) broadband color index and stellar metallicity [Fe/H]. These relations are valid for metallicities ranging from [Fe/H] = −0.5 to +0.1 dex and are accurate to ∼2%, ∼5%, and ∼4% for temperature, radius, and luminosity, respectively. Our results show that it is necessary to use metallicity-dependent transformations in order to properly convert colors into stellar temperatures, radii, and luminosities. Alternatively, we find no sensitivity to metallicity on relations we construct to the global properties of a star omitting color information, e.g., temperature–radius and temperature–luminosity. Thus, we are able to empirically quantify to what order the star's observed color index is impacted by the stellar iron abundance. In addition to the empirical relations, we also provide a representative look-up table via stellar spectral classifications using this collection of data. Robust examinations of single star temperatures and radii compared to evolutionary model predictions on the luminosity–temperature and luminosity–radius planes reveal that models overestimate the temperatures of stars with surface temperatures <5000 K by ∼3%, and underestimate the radii of stars with radii <0.7 R☉ by ∼5%. These conclusions additionally suggest that the models over account for the effects that the stellar metallicity may have on the astrophysical properties of an object. By comparing the interferometrically measured radii for the single star population to those of eclipsing binaries, we find that for a given mass, single and binary star radii are indistinguishable. However, we also find that for a given radius, the literature temperatures for binary stars are systematically lower compared to our interferometrically derived temperatures of single stars by ∼200 to 300 K. The nature of this offset is dependent on the validation of binary star temperatures, where bringing all measurements to a uniform and correctly calibrated temperature scale is needed to identify any influence stellar activity may have on the physical properties of a star. Lastly, we present an empirically determined H-R diagram using fundamental properties presented here in combination with those in Boyajian et al. for a total of 74 nearby, main-sequence, A- to M-type stars, and define regions of habitability for the potential existence of sub-stellar mass companions in each system.

Subfields: Astronomy and Astrophysics, Instrumentation

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In Astronomy and Astrophysics

1. D. Charbonneau
2. E. Gaidos
3. Timothy Morton
4. D. Huber
5. J. Johnson
6. A. Mann
7. Jon Fortney
8. C. Dressing

In Instrumentation

1. D. Charbonneau
2. Timothy Morton
3. E. Gaidos
4. D. Huber
5. A. Mann
6. J. Johnson
7. C. Dressing
8. Michael C. Liu

Citations in the corpus

• STELLAR AND PLANETARY PROPERTIES OF K2 CAMPAIGN 1 CANDIDATES AND VALIDATION OF 17 PLANETS, INCLUDING A PLANET RECEIVING EARTH-LIKE INSOLATION (2015, methodology): “This method was used because it is known to accurately reproduce empirical Teff values from long-baseline optical interferometry Boyajian et al. (2012).”
• AN EMPIRICAL CALIBRATION TO ESTIMATE COOL DWARF FUNDAMENTAL PARAMETERS FROM H-BAND SPECTRA (2014, methodology): “However, we include Gl 725B in our analysis of radius: while changing a star’s temperature affects the interferometrically-measured radius through the adopted limb darkening model, the effect is small (see Boyajian et al. 2012).”
• Improving PARSEC models for very low mass stars (2014, background): “These mechanisms may indicate that eclipsing binaries follow a different mass–radius relation than single field stars, although Boyajian et al. (2012) and Spada et al. (2013) find that their radii are indistinguishable.”
• THE OCCURRENCE OF POTENTIALLY HABITABLE PLANETS ORBITING M DWARFS ESTIMATED FROM THE FULL KEPLER DATASET AND AN EMPIRICAL MEASUREMENT OF THE DETECTION SENSITIVITY (2015, methodology): “Both Mann et al. (2013b) and Mart́ın et al. (2013) estimated stellar radii using empirical relations based on interferometric observations of low-mass stars (Boyajian et al. 2012).”
• The PASTEL catalogue: 2016 version (2016, background): “A new feature in the 2016 version of PASTEL is to include several recent references providing effective temperatures from angular diameters and total flux at Earth for 151 stars (261 determinations by Boyajian et al. 2012a,b, 2013, 2015; von Braun et al. 2014; Heiter et al. 2015).”
• NEAR-INFRARED METALLICITIES, RADIAL VELOCITIES, AND SPECTRAL TYPES FOR 447 NEARBY M DWARFS (2013, background): “Few M dwarfs are bright enough for direct measurement of their radii (e.g. Berger et al. 2006; Boyajian et al. 2012), and discrepancies between the observed radii and theoretical predictions persist (see Torres 2013, for a review).”
• 197 CANDIDATES AND 104 VALIDATED PLANETS IN K2's FIRST FIVE FIELDS (2016, methodology): “We estimate approximate spectral types (SpTs) using tabulated photometric relations (Kraus & Hillenbrand 2007; Pecaut & Mamajek 2013; Rodriguez et al. 2013) and convert SpTs into stellar radii (R*) based on interferometric studies (Boyajian et al. 2012).”
• A NEARBY M STAR WITH THREE TRANSITING SUPER-EARTHS DISCOVERED BY K2 (2015, methodology): “Stellar Parameters Mann et al. (2013b) motivate a set of temperature sensitive spectral indices spanning the visible, J-, H-, and K-bands that are calibrated using the M dwarf sample of Boyajian et al. (2012) with interferometrically measured radii.”
• LARGER PLANET RADII INFERRED FROM STELLAR “FLICKER” BRIGHTNESS VARIATIONS OF BRIGHT PLANET-HOST STARS (2014, background): “Whether this is a failing of the extrapolation of the F8log g relation to log g&4.5, or a manifestation of largerthan-predicted stellar radii for low-mass K and M stars as observed interferometrically (e.g., von Braun et al. 2014; Boyajian et al. 2012), remains to be determined.”
• SWEET-Cat: A catalogue of parameters for Stars With ExoplanETs - I. New atmospheric parameters and masses for 48 stars with planets (2013, methodology): “The surface gravities were derived using Newton’s law from the mass and the radius derived using the empirical relations of Boyajian et al. (2012).”
• INTRINSIC COLORS, TEMPERATURES, AND BOLOMETRIC CORRECTIONS OF PRE-MAIN-SEQUENCE STARS (2013, methodology): “We use photometry from Table 7 of Boyajian et al. (2012b), converting Johnson I to the Cousins system using the conversions in Bessell (1979) and converting Johnson JHK to the 2MASS system using the conversions of Carpenter (2001).”
• FUNDAMENTAL PROPERTIES OF STARS USING ASTEROSEISMOLOGY FROM KEPLER AND CoRoT AND INTERFEROMETRY FROM THE CHARA ARRAY (2012, background): “…in combination with a parallax, yields a linear radius and, when combined with an estimate for the bolometric flux, provides a direct measurement of a star’s effective temperature (see, e.g., Code et al. 1976; Boyajian et al. 2009; Baines et al. 2009; Boyajian et al. 2012a,b; Creevey et al. 2012).”
• PLANETARY CANDIDATES FROM THE FIRST YEAR OF THE K2 MISSION (2015, methodology): “Once we had an estimate of effective temperature, we used the Boyajian et al. (2012) temperature/radius relationship to estimate stellar radii.”
• ZODIACAL EXOPLANETS IN TIME (ZEIT). III. A SHORT-PERIOD PLANET ORBITING A PRE-MAIN-SEQUENCE STAR IN THE UPPER SCORPIUS OB ASSOCIATION (2016, methodology): “This method has been shown to reproduce Teff values for main-sequence M dwarfs derived from interferometry (Boyajian et al. 2012), but is poorly tested on PMS stars.”
• 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).”
• SPITZER OBSERVATIONS CONFIRM AND RESCUE THE HABITABLE-ZONE SUPER-EARTH K2-18b FOR FUTURE CHARACTERIZATION (2016, methodology): “Based on the SpeX spectrum, we estimate the stellar metallicity using empirical methods based on the spectroscopic indices and equivalent widths calibrated using M dwarfs that have wide, co-moving FGK companions with well determined [Fe/H] (Boyajian et al. 2012; Mann et al. 2013a).”
• THE TRANSITING EXOPLANET SURVEY SATELLITE: SIMULATIONS OF PLANET DETECTIONS AND ASTROPHYSICAL FALSE POSITIVES (2015, unknown): “The interferometric radius measurements are from Boyajian et al. (2012).”
• Gaia FGK benchmark stars: Effective temperatures and surface gravities (2015, methodology): “Boyajian et al. (2012b, 2013) also determined bolometric fluxes and effective temperatures for all of these stars.”