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Astron. Astrophys. 348, 897-909 (1999)

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Age determinations of main-sequence stars: combining different methods

R. Lachaume 1,2, C. Dominik 2, T. Lanz 3,4,5 and H.J. Habing 2

1 École Normale Supérieure, 45 rue d'Ulm, F-75230 Paris Cedex 05, France (lachaume@clipper.ens.fr)
2 Sterrewacht Leiden, University of Leiden, P.O. Box 9513, 2300 RA Leiden, The Netherlands (dominik@strw.leidenuniv.nl)
3 Sterrenkundig Instituut, University Utrecht, P.O. Box 80000, 3508 TA Utrecht, The Netherlands
4 NASA Goddard Space Flight Center, Code 681, Greenbelt, MD 20771, USA (lanz@stars.gsfc.nasa.gov)
5 Department of Astronomy, University of Maryland, College Park, MD 20742, USA

Received 18 January 1999 / Accepted 4 June 1999

Abstract

We have determined the age of a sample of nearby main-sequence stars with spectral types B9-K9. We have derived the stellar ages from five different age estimators: the location in the HR diagram compared to theoretical isochrones, the rotational velocity, the strength of chromospheric calcium emission lines, the stellar metallicity, and their space velocity. New calibrations consistent with recent theoretical isochrones are provided for the last four indicators. For hot stars, isochrones are the best indicator, while stellar rotation is best for cool stars. However, many stars require in fact a combination of different methods to properly bracket their actual age. We also discuss the uncertainties involved, in particular those in using isochrones, and we find that these uncertainties are often underestimated in the literature.

Key words: stars: activity – stars: chromospheres – stars: evolution – stars: rotation

Send offprint requests to: C. Dominik

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© European Southern Observatory (ESO) 1999

Online publication: August 13, 199
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