Hostname: page-component-586b7cd67f-r5fsc Total loading time: 0 Render date: 2024-11-28T08:00:21.304Z Has data issue: false hasContentIssue false
  • English
  • Français

Hipparcos subdwarfs and globular cluster ages: towards reliable absolute ages

Published online by Cambridge University Press:  25 May 2016

F. Pont ,
M. Mayor  and
C. Turon
F. Pont
Affiliation:
Geneva Observatory, Sauverny, Switzerland
M. Mayor
Affiliation:
Geneva Observatory, Sauverny, Switzerland
C. Turon
Affiliation:
Observatoire de Paris, Meudon, France

Abstract

Core share and HTML view are not available for this content. However, as you have access to this content, a full PDF is available via the ‘Save PDF’ action button.

The maximum age of galactic globular clusters provides the best observational constraint on the minimum age of the Universe. One of the main “missing link” in the globular cluster age determination has been the lack of a precise calibration, with local subdwarfs, of the position of the subdwarf sequence at different [Fe/H].

Hipparcos data may change this situation. As many precise parallaxes become available for local subdwarfs, the distance to globular clusters can be estimated directly from ZAMS fitting to the subdwarf locus. The ages can then be inferred from the turnoff luminosity (a robust prediction of stellar evolution models), rather than using secondary indicators such as Horizontal-Branch position, or indicators depending on the uncertain colour scale such as turnoff colour.

Combining Hipparcos parallaxes with [Fe/H] values determined with the CORAVEL spectrometer, we are studying the position of the subdwarfs in the Colour-Magnitude Diagram from a sample of more than 900 subdwarf candidates. Preliminary results are presented here. It is shown that the distances of many subdwarfs had been underestimated in previous studies, mainly because a large fraction of them is in fact evolved off the main sequence into the turnoff or the subgiant branch.

Type
Stellar Ages
Information
Symposium - International Astronomical Union , Volume 189: Fundamental Stellar Properties: The Interaction Between Observation and Theory , 1997 , pp. 433 - 438
Copyright
Copyright © Kluwer 1997 

References

Carney, B.W., Latham, D.W., Laird, J.B. et al. 1994, AJ 107, 2240 (C94) Google Scholar
d'Antona, F., Mazzitelli, I., 1996, ApJ 456, 329 Google Scholar
Edvaxdsson, B., Andersen, J., Gustafsson, B. et al., 1993, A&A 275, 101 (E93) Google Scholar
Mayor, M., 1980, A&A 87, L1 Google Scholar
Ryan, S.G., Norris, J.E., 1991, AJ 101, 1835 Google Scholar
Zinn, R., West, M.J., 1984, ApJSS 55, 45 Google Scholar