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Issue A&A Volume 381, Number 2, January II 2002 Page(s) 524 - 538 Section Stellar atmospheres DOI 10.1051/0004-6361:20011493

A&A 381, 524-538 (2002)
DOI: 10.1051/0004-6361:20011493

A standard stellar library for evolutionary synthesis

III. Metallicity calibration

P. Westera¹, T. Lejeune², R. Buser¹, F. Cuisinier³ and G. Bruzual<sup>4

1</sup>  Astronomisches Institut der Universität Basel, Venusstrasse 7, 4102 Binningen, Switzerland
    e-mail: westera@astro.unibas.ch, buser@astro.unibas.ch
²  Observatório Astronómico da Universidade de Coimbra, Portugal
    e-mail: lejeune@mat.uc.pt
³  Depto. de Astronomia, Universidade Federal do Rio de Janeiro, Brazil
    e-mail: cuisinie@sun1.ov.ufrj.br
⁴  Centro de Investigaciones de Astronomía, Mérida, Venezuela
    e-mail: bruzual@cida.ve

(Received 17 July 2001 / Accepted 19 October 2001 )

Abstract
We extend the colour calibration of the widely used BaSeL standard stellar library (Lejeune et al. 1997, 1998) to non-solar metallicities, down to dex. Surprisingly, we find that at the present epoch it is virtually impossible to establish a unique calibration of UBVRIJHKL colours in terms of stellar metallicity which is consistent simultaneously with both colour-temperature relations and colour-absolute magnitude diagrams (CMDs) based on observed globular cluster photometry data and on published, currently popular standard stellar evolutionary tracks and isochrones. The problem appears to be related to the long-standing incompleteness in our understanding of convection in late-type stellar evolution, but is also due to a serious lack of relevant observational calibration data that would help resolve, or at least further significant progress towards resolving this issue. In view of the most important applications of the BaSeL library, we here propose two different metallicity calibration versions: (1) the "WLBC 99" library, which consistently matches empirical colour-temperature relations and which, therefore, should make an ideal tool for the study of individual stars; and (2), the "PADOVA 2000" library, which provides isochrones from the Padova 2000 grid (Girardi et al. 2000) that successfully reproduce Galactic globular-cluster colour-absolute magnitude diagrams and which thus should prove particularly useful for studies of collective phenomena in stellar populations in clusters and galaxies.

Key words: catalogs -- stars: abundances -- stars: atmospheres -- stars: fundamental parameters

Offprint request: R. Buser, buser@astro.unibas.ch

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