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

Creators: North, J. R.; Davis, J.; Bedding, T. R.; Ireland, M. J.; Jacob, A. P.; O'Byrne, J.; Owens, S. M.; Robertson, J. G.; Tango, W. J.; Tuthill, P. G.

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.

Additional Information

© 2007 The Authors. Journal compilation © 2007 RAS. Accepted 2007 June 20. Received 2007 June 18; in original form 2007 May 29. This research has been jointly funded by The University of Sydney and the Australian Research Council as part of the Sydney University Stellar Interferometer (SUSI) project. JRN and APJ acknowledge the support provided by a University of Sydney Postgraduate Award. APJ and SMO were supported by a Denison Postgraduate Award. This research has made use of the SIMBAD data base, operated at CDS, Strasbourg, France. This paper has been typeset from a TEX/LATEX file prepared by the author.

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