THE HEI SURFACE DISTRIBUTION OF THE CP2 STAR CU VIRGINIS

Based on Coude spectra obtained with the 2.24-m telescope at MKO, we d erive a map of the surface distribution of helium for the B9p Si star CU Vir. The helium abundance varies by more than one order of magnitud e over the surface of this star and is concentrated in one large spot and a second, less pronounced, spot. This pattern is in anti-phase to the silicon surface distribution and is similar to what we have found for ET And, which is another Si-star. We compare our observed equivale nt width measurements and synthetic ones, which we have derived from o ur map, with previously published data and can corroborate the long-te rm stability of the spots. CU Vir is the second CP2 star, for which a helium surface map is available.