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The CHARA Array Angular Diameter of HR 8799 Favors Planetary Masses for its Imaged Companions

Baines, Ellyn K. and White, Russel J. and Huber, Daniel and Jones, Jeremy and Boyajian, Tabetha and McAlister, Harold A. and ten Brummelaar, Theo A. and Turner, Nils H. and Sturmann, Judit and Sturmann, Laszlo and Goldfinger, P. J. and Farrington, Christopher D. and Riedel, Adric R. and Ireland, Michael and von Braun, Kaspar and Ridgway, Stephen T. (2012) The CHARA Array Angular Diameter of HR 8799 Favors Planetary Masses for its Imaged Companions. Astrophysical Journal, 761 (1). Art. No. 57. ISSN 0004-637X. doi:10.1088/0004-637X/761/1/57.

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HR 8799 is an hF0 mA5 γ Doradus-, λ Bootis-, Vega-type star best known for hosting four directly imaged candidate planetary companions. Using the CHARA Array interferometer, we measure HR 8799's limb-darkened angular diameter to be 0.342 ± 0.008 mas (an error of only 2%). By combining our measurement with the star's parallax and photometry from the literature, we greatly improve upon previous estimates of its fundamental parameters, including stellar radius (1.44 ± 0.06 R_☉), effective temperature (7193 ± 87 K, consistent with F0), luminosity (5.05 ± 0.29 L_☉), and the extent of the habitable zone (HZ; 1.62-3.32 AU). These improved stellar properties permit much more precise comparisons with stellar evolutionary models, from which a mass and age can be determined, once the metallicity of the star is known. Considering the observational properties of other λ Bootis stars and the indirect evidence for youth of HR 8799, we argue that the internal abundance, and what we refer to as the effective abundance, is most likely near solar. Finally, using the Yonsei-Yale evolutionary models with uniformly scaled solar-like abundances, we estimate HR 8799's mass and age considering two possibilities: 1.516^(+0.038)_(–0.024) M_☉ and 33^(+7)_(–13.2) Myr if the star is contracting toward the zero-age main sequence or 1.513^(+0.023)_(–0.024_ M_☉ and 90^(+381)_(–50) Myr if it is expanding from it. This improved estimate of HR 8799's age with realistic uncertainties provides the best constraints to date on the masses of its orbiting companions, and strongly suggests they are indeed planets. They nevertheless all appear to orbit well outside the HZ of this young star.

Item Type:Article
Related URLs:
URLURL TypeDescription
Baines, Ellyn K.0000-0002-5684-3424
White, Russel J.0000-0001-5313-7498
Huber, Daniel0000-0001-8832-4488
Boyajian, Tabetha0000-0001-9879-9313
ten Brummelaar, Theo A.0000-0002-0114-7915
Farrington, Christopher D.0000-0001-9939-2830
Riedel, Adric R.0000-0003-1645-8596
Ireland, Michael0000-0002-6194-043X
von Braun, Kaspar0000-0002-5823-4630
Additional Information:© 2012 American Astronomical Society. Received 2012 July 3; accepted 2012 September 29; published 2012 November 21. We thank Gerard van Belle for his insight on the nature of HR 8799’s pirouette through space. The CHARA Array is funded by the National Science Foundation through NSF grant AST-0606958 and by Georgia State University through the College of Arts and Sciences, and S.T.R. acknowledges partial support by NASA grant NNH09AK731. This research has made use of the SIMBAD database, operated at CDS, Strasbourg, France. This publication makes use of data products from the Two Micron All Sky Survey, which is a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center/California Institute of Technology, funded by the National Aeronautics and Space Administration and the National Science Foundation.
Funding AgencyGrant Number
Georgia State UniversityUNSPECIFIED
Subject Keywords:planetary systems; stars: fundamental parameters; stars: individual (HR 8799); techniques: high angular resolution; techniques: interferometric
Issue or Number:1
Record Number:CaltechAUTHORS:20130109-084131857
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Official Citation:The CHARA Array Angular Diameter of HR 8799 Favors Planetary Masses for its Imaged Companions Ellyn K. Baines et al. 2012 ApJ 761 57
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:36258
Deposited By: Ruth Sustaita
Deposited On:09 Jan 2013 17:08
Last Modified:09 Nov 2021 23:21

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