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Astron. Astrophys. 341, 857-866 (1999)

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2. Model colours

The BaSeL models cover a large range of fundamental parameters: 2000 K [FORMULA] [FORMULA] [FORMULA] 50,000 K, -1.02 [FORMULA] [FORMULA] [FORMULA] 5.5, and -5.0 [FORMULA] [FORMULA] [FORMULA] +1.0. This library combines theoretical stellar energy distributions which are based on several original grids of blanketed model atmospheres, and which have been corrected in such a way as to provide synthetic colours consistent with extant empirical calibrations at all wavelengths from the near-UV through the far-IR (see Lejeune et al. 1997, 1998a). For our purpose, we have used the new version of the BaSeL models for which the correction procedure of the theoretical spectra has been extended to higher temperatures ([FORMULA] [FORMULA] 12,000 K), using the [FORMULA]-(B-V) calibration of Flower (1996), and to shorter wavelengths (Lejeune et al. 1998b). Because the correction procedure implies modulations of the (pseudo-)continuum which are smooth between the calibration wavelengths, the final grid provides colour-calibrated flux distributions (9.1 [FORMULA] 160,000 nm, with a mean resolution of 1 [FORMULA] 2 nm from the UV to the visible) which are also suitable for calculating medium-band synthetic photometry, such as Strömgren colours. Thus, synthetic Strömgren photometry was performed using the passband response functions ([FORMULA]) given in Schmidt-Kaler (1982). Theoretical (u-b), (b-y), m1 [FORMULA] (v-b)-(b-y), and c1 [FORMULA] (u-v)-(v-b) indices have been computed, where the zero-points were defined by matching the observed colours (u-b [FORMULA] 1.411, b-y [FORMULA] 0.004, m1 [FORMULA] 0.157, c1 [FORMULA] 1.089; Hauck & Mermilliod 1980) of Vega with those predicted by the corresponding Kurucz (1991) model for [FORMULA] [FORMULA] 9400 K, [FORMULA] [FORMULA] 3.90, [FORMULA] [FORMULA] -0.50.

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© European Southern Observatory (ESO) 1999

Online publication: December 16, 1998