Spectral analysis of four multi mode pulsating sdB stars

Four members of the class of pulsating sdB stars (EC 14026 stars) are analysed from Keck HIRES spectra using line blanketed NLTE and LTE model atmospheres. Atmospheric parameters (T-eff, log g, He/H), metal abundances and rotational velocities are determined. All programme stars are found to be helium deficient, with He/H ranging from 1/80 solar for Feige48 to 1/3 solar for PG1219+534. Most metals are also depleted. The abundances of C, O, Ne, Mg, Al and Si in the high gravity programme stars KPD2109+4401 and PG1219+534 are considerably lower than in the lower gravity stars Feige48 and PG1605+072. This results strongly point towards the action of diffusion processes. The abundances could be explained by an equilibrium between gravitational settling and radiative levitation. Surprisingly iron is found to be solar to within error limits in all programme stars irrespective of their gravity. In PG1605+072 the spectral lines are broadened, probably due to rotation and v(rot) sini = 39 km/s is derived. For the three other programme stars the metal lines are very sharp and v(rot) sini has to be very low (v(rot) sini < 5-10 km/s).