SIMBAD references

The oxygen λ7771–4 Å triplet is a good indicator of luminosity in A–G supergiants. However, its strength also depends on other atmospheric parameters. In this study, we present the luminosity calibrations where, for the first time, the effects of the effective temperature, microturbulent velocity, surface gravity and the abundance have been disentangled. The calibrations are derived on the basis of a data set of high-dispersion spectra of 60 yellow supergiants with highly reliable luminosities and accurate atmospheric parameters. This allowed us to bring the uncertainty of the triplet-based absolute magnitudes down to 0.26 mag. The calibrations are suitable for spectral types F0–K0 and luminosity classes I–II, covering absolute magnitudes M_vfrom -1.0 to -10 mag.