Description
With the {Delta}a photometric system, it is possible to study very distant galactic and even extragalactic clusters with a high level of accuracy. The new calibration presented is a powerful extension. Because no a-priori reddening-free photometric parameters are available for the investigated spectral range, we have applied the dereddening calibrations of the Stromgren uvby{beta} system and compared them with extinction models for the Milky Way. We derived an empirical temperature calibration for the {Delta}a photometric system for A-type to mid F-type with a mean of the error for the whole sample of {Delta}T(eff) is 134K which is lower than the value in Paper I (Paunzen et al., 2005, Cat. <J/A+A/444/941>) for hotter stars. No statistically significant effect of the rotational velocity on the precision of the calibration was found.
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