SIMBAD references

A revised effective temperature calibration for the DDO photometric system is presented. Recently published photometric and spectroscopic observations of field and open cluster G and K stars allow a better definition of the solar-abundance fiducial relation in the DDO C_0(45-48) vs C_0(42-45) diagram. The ability of the DDO system to predict MK spectral types of G and K giants is demonstrated. The new DDO effective temperature calibration reproduces satisfactorily the infrared temperature scale of Bell and Gustafsson (1989). It is shown that Osborn's (1979) calibration underestimates the effective temperatures of K giants by ∼170 K and those of late-type dwarfs by ∼150 K.