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Stellar Diameters and Temperatures. II. Main-sequence K- and M-stars

Boyajian, Tabetha S. and von Braun, Kaspar and van Belle, Gerard and McAlister, Harold A. and ten Brummelaar, Theo A. and Kane, Stephen R. and Muirhead, Philip S. and Jones, Jeremy and White, Russel and Schaefer, Gail and Ciardi, David and Henry, Todd and Lόpez-Morales, Mercedes and Ridgway, Stephen and Gies, Douglas and Jao, Wei-Chun and Rojas-Ayala, Bárbara and Parks, J. Robert and Sturmann, Laszlo and Sturmann, Judit and Turner, Nils H. and Farrington, Chris and Goldfinger, P. J. and Berger, David H. (2012) Stellar Diameters and Temperatures. II. Main-sequence K- and M-stars. Astrophysical Journal, 757 (2). Art. No. 112. ISSN 0004-637X.

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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.

Item Type:Article
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URLURL TypeDescription 2014 August 1 2017 August 20 Paper
Boyajian, Tabetha S.0000-0001-9879-9313
von Braun, Kaspar0000-0002-5823-4630
van Belle, Gerard0000-0002-8552-158X
ten Brummelaar, Theo A.0000-0002-0114-7915
Kane, Stephen R.0000-0002-7084-0529
Muirhead, Philip S.0000-0002-0638-8822
White, Russel0000-0001-5313-7498
Ciardi, David0000-0002-5741-3047
Lόpez-Morales, Mercedes0000-0003-3204-8183
Jao, Wei-Chun0000-0003-0193-2187
Farrington, Chris0000-0001-9939-2830
Additional Information:© 2012 American Astronomical Society. Received 2012 April 15; accepted 2012 August 8; published 2012 September 10. We thank Greg Feiden for his helpful conversations and advice regarding the Dartmouth stellar models. We thank the referee, whose comments undoubtedly improved the manuscript significantly. T.S.B. acknowledges support provided by NASA through Hubble Fellowship grant No. HST-HF-51252.01 awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under contract NAS 5-26555. S.T.R. acknowledges partial support from NASA grant NNH09AK731. The CHARA Array is funded by the National Science Foundation through NSF grant AST-0908253 and by Georgia State University through the College of Arts and Sciences. This research has made use of the SIMBAD literature database, operated at CDS, Strasbourg, France, and of NASA’s Astrophysics Data System. This research has also made use of the VizieR catalog access tool, CDS, Strasbourg, France.
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
NASA Hubble FellowshipHST-HF-51252.01
Space Telescope Science InstituteUNSPECIFIED
Subject Keywords:Hertzsprung-Russell and C-M diagrams; infrared: stars; planetary systems; stars: atmospheres; stars: fundamental parameters; stars: general; stars: late-type; stars: low-mass; techniques: high angular resolution; techniques: interferometric
Issue or Number:2
Record Number:CaltechAUTHORS:20121031-103538875
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Official Citation:Stellar Diameters and Temperatures. II. Main-sequence K- and M-stars Tabetha S. Boyajian et al. 2012 ApJ 757 112
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:35205
Deposited By: Jason Perez
Deposited On:31 Oct 2012 19:11
Last Modified:27 Nov 2019 19:08

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