SIMBAD references

The red lines of the OI multiplet at λ=7773A are observed at high resolution and their rotational variation is recorded for a sample of nine magnetic Ap stars. These lines are found to be weaker than for normal A stars. The irregular distribution of oxygen on the stellar surface is connected to the magnetic geometry for the stars HD 25823 (41 Tau), HD 74521 (49 Cnc), HD 112185 (ε UMa), HD 112413 (α² CVn), and HD 125248 (CS Vir). For four of these stars, it is clearly established that oxygen is concentrated around a magnetic polar region. The interpretation of the observed trends adds new constraints to the theory of radiative diffusion of oxygen in Ap stars.