Surface Mapping of the he & SI Distribution of Four B Stars

In the framework of a long-term high-resolution spectroscopic monitoring campaign of slowly pulsating B stars we have discovered four spotted mid-B main-sequence stars exhibiting clear line-profile variability of selected He and Si lines. We derive the rotational period which is of the order of 1-2 days of these stars with a high precision. We perform surface mapping which allows us to derive the distribution of the helium and silicon on the stellar surface. We find evidence for the presence of large spots in all four stars. He overabundance is accompanied with Si underabundance or vice versa in the spots. Our data are usefull to test current diffusion theories which have been developed for spotted A-type stars. Our stars have effective temperatures around 17000K which makes them among the hottest known so far with such clear spotted patterns. It would be most valuable to have magnetic field measurements for the four stars in order to explain the surface element distribution.