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Astron. Astrophys. 328, 349-360 (1997)

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5. Solar colours

While, the [FORMULA] and [FORMULA] of the Sun are very well known, the uvby colours for the Sun are not. Published values of [FORMULA] range from [FORMULA] (Edvardsson et al. 1993) to [FORMULA] (Gray 1992). An extensive literature search revealed no values of [FORMULA] and [FORMULA] for the Sun. Therefore, we cannot use the same procedures to obtain grid [FORMULA] and [FORMULA] values as used above. Hence, models with [FORMULA] = 5777 K and [FORMULA] = 4.44 were used to calculate values of [FORMULA] for the three sets of grids; CM gives [FORMULA] = 0.393 [FORMULA] 0.006, MLT noOV gives [FORMULA] = 0.400 [FORMULA] 0.006, and MLT OV gives [FORMULA] = 0.414 [FORMULA] 0.006.

The CM solar model is not in agreement with the observed colours. It appears that the solar colours are in better agreement with those obtained using the MLT noOV or MLT OV models. In fact, the MLT OV models appear to give the best agreement with the observed colours. However, Fig. 2 does not appear to support this, unless the discrepancy starts to manifest itself at [FORMULA] [FORMULA] 6000 K. The fundamental stars go as cool as 6290 K, but the non-fundamental stars go down to 5500 K. From the results shown in Fig. 4, it might appear that CM and MLT noOV solar models should be reliable, while the MLT OV should not. The opposite is indicated by the solar colours! This conclusion was found by Castelli et al. (1997), who, however, stated that the uncertainties in the solar colours preclude any definite conclusion.

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© European Southern Observatory (ESO) 1997

Online publication: March 24, 1998