Spectral analysis of multi mode pulsating sdB stars II. Feige 48, KPD 2109+4401 and PG 1219+534

Three members df the new class of pulsating sdB stars (sdBV or EC 14026 sta rs) are analysed from Keck HIRES spectra using line blanketed NLTE and LTE model atmospheres. Atmospheric parameters (T-eff, log g, log(He/H)), metal abundances and rotational velocities are determined. A careful investigatio n of several temperature indicators, i.e. line profile fitting of Balmer an d helium lines, the ionization equilibria of helium, nitrogen and silicon g ave consistent results for Feige 48 and KPD2109+4401 to within a few hundre d Kelvin. However, for PG 1219+534 considerably higher effective temperatur e estimates were derived from the ionization equilibria of nitrogen (36 800 K) and helium (34 300 K) than from the Balmer line profile fitting (33 200 K). A systematic difference in the gravity derived from NLTE and LTE model s was observed, the NLTE gravities being slightly lower, by up to 0.1 dex, than the LTE results. As is typical for sdB stars, all programme stars are found to be helium def icient, with a helium abundance ranging from 1/80 solar for Feige 48 to 1/3 solar for PG 1219+534, probably due to diffusion. Most metals are also dep leted. The abundances of C, O, Ne, Mg, Al and Si in the high gravity progra mme stars KPD 2109+4401 and PG 1219+534 are considerably lower than in the lower gravity stars Feige 48 and PG 1605+072 (Heber et al. 1999a) which cou ld be explained by an equilibrium between gravitational settling and radiat ive levitation. Surprisingly iron is solar to within error limits in all pr ogramme stars irrespective of their gravity, confirming predictions from di ffusion calculations of Charpinet et al. (1997). The metal lines are very sharp and allow the microturbulent velocity to be constrained to be lower than 5 kms(-1) (KPD 2109+4401, PG 1219+534). Also t he projected rotational velocities have to be very low (v(rot) sini < 10 km s(-1)). For Feige 48 the limits are even tighter (v(micro) <less than or e qual to> 3 km s(-1), v(rot) sini less than or equal to 5 km s(-1)).