The UV resonance lines of three hot Ap stars: HD 133029, HD 175362 and HD 219749
High resolution spectra of the Ap stars HD 133929, HD 175329 and HD 219749 were obtained during two 16 hour shifts with the IUE satellite at Goddard Space Flight Center. Stellar wind, extended atmosphere in rigid corotation with the stellar surface, and the influence of the strong magnetic field on the upper part of the atmosphere would explain the shape and the strength of the resonance lines. The resonance lines of HD 175362 in particular show very peculiar behavior. The necessary driving forces for the expanding envelope are not compatible with the diffusion theory of the Ap atmospheres.
Rakos, K. D.↗