Institution(s): 1. Kavli Institute for Astronomy and Astrophysics at Peking University
We present empirical metallicity-dependent calibrations of effective temperature against colours for dwarfs of luminosity classes IV and V and giants of luminosity classes II and III, based on a collection of about two hundred nearby stars with direct effective temperature measurements of better than 2.5 per cent from the literature. The calibrations are valid for an effective temperature range 3,100 – 10,000 K for dwarfs of spectral types M5 to A0 and 3,100 – 5,700 K for giants of spectral types K5 to G5. A total of twenty-one colours for dwarfs and eighteen colours for giants of bands between four photometric systems, i.e. the Johnson (UBV RJIJJHK), the Cousins (RCIC), the Sloan Digital Sky Survey (SDSS, gr) and the Two Micron All Sky Survey (2MASS, JHKs), have been calibrated, respectively. Restricted by the metallicity range of the current sample, the calibrations are mainly applicable for disk stars ([Fe/H] ~ −1.0). The normalized percentage residuals of the calibrations are typically 2.0 and 1.5 per cent for dwarf and giant stars, respectively. Some systematic discrepancies of different levels are found between the current scales and those available in the literature (e.g. those based on the infrared flux method IRFM or spectroscopy). Based on the current calibrations, we have re-determined the colours of the Sun. We have also investigated the potential systematic errors in the estimates of effective temperature delivered by the current on-going large scale low- to intermediate-resolution stellar spectroscopic surveys. We propose that colour (g − Ks) calibrated in the current work can be an invaluable tool for the estimation of stellar effective temperature for the current/upcoming large scale stellar spectroscopic surveys. With the temperature yielded by this method , surface gravity (e.g. mass, density) determined by newly asteroseismology knowledge and metallicity ([Fe/H]) from high-resolution spectroscopy, we can give more constrains to the stellar evolution model.