The spectral energy distributions for pure-hydrogen (DA) hot white dwarfs can be accurately predicted by model atmospheres. This makes it possible to define spectrophotometric calibrators by scaling the theoretical spectral shapes with broad-band photometric observations - a strategy successfully exploited for the spectrographs onboard the Hubble

Aims: A detailed study is presented, including estimates of the impact on elemental abundance analysis, of the non-local thermodynamic equilibrium (non-LTE) formation of the high-excitation neutral oxygen 777 nm triplet in model atmospheres representative of stars with spectral types F to K. Methods: We have applied the statistical equilibrium code

We present the first synthesis of Mn I lines in realistic multi-component magnetized quiet Sun atmospheres, including variation of magnetic field strength, magnetic field direction, plasma velocity, and coupling between magnetic field and thermodynamics. All synthesized Mn I lines weaken for strong magnetic fields. A detailed analysis of the Mn I

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