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Paper: Clouds of Chemical Elements in High Atmospheric Layers of ApBp Stars
Volume: 479, Progress in Physics of the Sun and Stars
Page: 35
Authors: Alecian, G.
Abstract: Models that include atomic diffusion in chemically peculiar stars have mostly considered internal layers and the usual line-forming layers in atmospheres. Indeed, the main observable effects of diffusion processes (and of the subsequent abundance stratifications) are expected to come from these layers. However, recent progress in modeling and new observations, allow a better understanding of the richness of phenomena that may be related to atomic diffusion in high atmospheric layers (above τ ≈ 10–4). Clouds/spots of chemical elements may form in those layers, even in stars labelled as non-magnetic (HgMn). In HgMn stars, such spots could be due to weak magnetic fields, and would be situated above a background of homogeneous element stratifications that cause the usual and well-known overabundances of, for instance, iron peak elements. According to current models, the effects of such inhomogeneities are compatible not only with peculiarities observed in spectra but also with peculiar variabilities due to waves propagating in these inhomogeneous media.
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