Volume 380, Issue 1 pp. L80-L83

The radius and mass of the subgiant star β Hyi from interferometry and asteroseismology

J. R. North

Corresponding Author

J. R. North

School of Physics, University of Sydney, Sydney, NSW 2006, Australia

E-mail: [email protected]Search for more papers by this author
J. Davis

J. Davis

School of Physics, University of Sydney, Sydney, NSW 2006, Australia

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T. R. Bedding

T. R. Bedding

School of Physics, University of Sydney, Sydney, NSW 2006, Australia

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M. J. Ireland

M. J. Ireland

School of Physics, University of Sydney, Sydney, NSW 2006, Australia

Planetary Science, MS 150-21, Caltech, 1200 E. California Blvd, Pasadena, CA 91125, USA

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A. P. Jacob

A. P. Jacob

School of Physics, University of Sydney, Sydney, NSW 2006, Australia

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J. O'Byrne

J. O'Byrne

School of Physics, University of Sydney, Sydney, NSW 2006, Australia

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S. M. Owens

S. M. Owens

School of Physics, University of Sydney, Sydney, NSW 2006, Australia

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J. G. Robertson

J. G. Robertson

School of Physics, University of Sydney, Sydney, NSW 2006, Australia

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W. J. Tango

W. J. Tango

School of Physics, University of Sydney, Sydney, NSW 2006, Australia

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P. G. Tuthill

P. G. Tuthill

School of Physics, University of Sydney, Sydney, NSW 2006, Australia

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First published: 25 July 2007
Citations: 2

ABSTRACT

We have used the Sydney University Stellar Interferometer to measure the angular diameter of β Hydri. This star is a nearby G2 subgiant the mean density of which was recently measured with high precision using asteroseismology. We determine the radius and effective temperature of the star to be 1.814 ± 0.017 R (0.9 per cent) and 5872 ± 44 K (0.7 per cent) respectively. By combining the radius with the mean density, as estimated from asteroseismology, we make a direct estimate of the stellar mass. We find a value of 1.07 ± 0.03 M (2.8 per cent), which agrees with published estimates based on fitting in the Hertzsprung–Russell diagram, but has much higher precision. These results place valuable constraints on theoretical models of β Hyi and its oscillation frequencies.

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