Teff against colours calibrations

We present empirical metallicity-dependent calibrations of effective temperature against colours for dwarfs of luminosity classes IV and V and for giants of luminosity classes II and III, based on a collection from the literature of about two hundred nearby stars with direct effective temperature measurements of better than 2.5 per cent. The calibrations are valid for an effective temperature range 3100-10000K for dwarfs of spectral types M5 to A0 and 3100-5700K for giants of spectral types K5 to G5.

A total of 21 colours for dwarfs and 18 colours for giants of bands of four photometric systems, i.e. the Johnson (UBVR_J_I_J_JHK), the Cousins (R_C_I_C_), the Sloan Digital Sky Survey (gr) and the Two Micron All Sky Survey (JHKs), have been calibrated. Restricted by the metallicity range of the current sample, the calibrations are mainly applicable for disc stars ([Fe/H]>~-1.0). The normalized percentage residuals of the calibrations are typically 2.0 and 1.5 per cent for dwarfs and giants, respectively.