A&A Supplement Series, Vol. 125, October II, 229-246
Received September 23, 1996; accepted January 2, 1997
Th. Lejeune 
- F. Cuisinier 
- R. Buser 
Send offprint request: R. Buser
Astronomisches
Institut der Universität Basel, Venusstr. 7,
CH-4102 Binningen, Switzerland
Observatoire
de Strasbourg, 11, rue de l'Université,
F-67000 Strasbourg, France
Instituto Astronomico e
Geofisico da Universidade Sao Paulo, Departamento de
Astronomia, Caixa Postal 9638, 01065-970 Sao Paulo SP,
Brasil
We present a comprehensive hybrid library of synthetic stellar spectra
based on three original grids of model atmosphere spectra by Kurucz
(1995), Fluks et al. (1994), and Bessell et al.
(1989, 1991), respectively. The combined library has been
intended for multiple-purpose synthetic photometry applications and was
constructed according to the precepts adopted by Buser & Kurucz
(1992): (i) to cover the largest possible ranges in stellar
parameters (
, 
, and [M/H]); (ii) to provide flux
spectra with useful resolution on the uniform grid of wavelengths
adopted by Kurucz (1995); and (iii) to provide synthetic
broad-band colors which are highly realistic for the largest possible
parameter and wavelength ranges.
Because the most astrophysically relevant step consists in
establishing a realistic library, the corresponding color
calibration is described in some detail. Basically, for each value of
the effective temperature and for each wavelength, we calculate the
correction function that must be applied to a (theoretical)
solar-abundance model flux spectrum in order for this to yield
synthetic UBVRIJHKL colors matching the (empirical) color-temperature
calibrations derived from observations. In this way, the most
important systematic differences existing between the original model
spectra and the observations can indeed be eliminated. On the other
hand, synthetic UBV and Washington ultraviolet excesses
and 
and 
obtained from the original giant and dwarf model spectra are in
excellent accord with empirical metal-abundance calibrations (Lejeune
& Buser 1996). Therefore, the calibration algorithm is designed
in such a way as to preserve the original differential grid
properties implied by metallicity and/or luminosity changes in the
new library, if the above correction function for a solar-abundance
model of a given effective temperature is also applied to models of
the same temperature but different chemical compositions [M/H] and/or
surface gravities .
While the new library constitutes a first-order approximation to the program set out above, it will be allowed to develop toward the more ambitious goal of matching the full requirements imposed on a standard library. Major input for refinement and completion is expected from the extensive tests now being made in population and evolutionary synthesis studies of the integrated light of globular clusters (Lejeune 1997) and galaxies (Bruzual et al. 1997).
keywords: atlases -- stars: fundamental parameters