We have obtained strong evidence for an inhomogeneous distribution of lithium, or whatever element responsible for the Li blend, on the surface of the roAp star HD 83368. Another Ap star, HD 3980, shows a similar behaviour of the variations of the lithium blend (Faraggiana et al. 1996).
To understand why lithium is concentrated in spots, detailed calculations of diffusion in the presence of a magnetic field would be necessary. At the magnetic poles, the Li concentration in spots might be due to ambipolar diffusion of hydrogen, as suggested by Babel (1993). New observations would be useful in order to cover more completely the rotational phases in selected spectral regions, for studying the geometry of the spots, as well as the abundance distribution of Li and other elements on the surface of HD 83368 and other Ap stars.
© European Southern Observatory (ESO) 1998
Online publication: April 20, 1998