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Astron. Astrophys. 330, 1077-1079 (1998)

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Research Note

Beta Hydri (G2 IV): a revised age for the closest subgiant *

D. Dravins 1, L. Lindegren 1 and D.A. VandenBerg 2

1 Lund Observatory, Box 43, S-22100 Lund, Sweden
2 Department of Physics and Astronomy, University of Victoria, P.O. Box 3055, Victoria, B.C., Canada V8W 3P6

Received 12 June 1997 / Accepted 27 June 1997


The secular evolution of solar-type atmospheres may be studied through comparisons of the current Sun with old solar-type stars of known age. Among the few such stars in the solar Galactic neighborhood, [FORMULA]  Hydri (G2 IV) stands out as a normal single star with an advanced age. Previous age determinations ([FORMULA]  Gy) were based on the old ground-based parallax of 153 mas. The new Hipparcos value of [FORMULA]  mas implies an absolute magnitude [FORMULA], 0.3 mag brighter than previously believed. New evolutionary calculations produce best-fit models with ages around 6.7 Gy. Although the Hipparcos data thus lead to a significant reduction of its estimated age, [FORMULA]  Hyi remains an old star.

Key words: space astrometry – stars: evolution – stars: individual: fi Hyi – stars: late-type

* Based on observations made with the ESA Hipparcos astrometry satellite

Send offprint requests to: D. Dravins

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© European Southern Observatory (ESO) 1998

Online publication: January 27, 1998