2006BaltA..15..243G

We present the analysis of 200 high-resolution and 150 low-resolution spectra of the pulsating subdwarf close binary KPD 1930+2752 obtained with the Keck and the Calar Alto 2.2 m telescopes. Using metal-rich, line blanketed LTE model atmospheres the atmospheric parameters T_eff = 35500±500 K, logg = 5.56±0.05 and log He/H = -1.48±0.02 were derived. The radial velocity curve was measured and combined with all available published and unpublished radial velocity data in order to get results of high accuracy: K = 341±1 km/s, P = 0.0950933±0.0000015 d. For the first time we measured the projected rotational velocity. The preliminary result is v_rotsin i = 97±9 km/s (3σ). Since the rotation of the sdB star is very likely tidally locked to the orbit, we can constrain the inclination of the system. Assuming the companion to be a white dwarf, the mass of the sdB is limited from 0.44 M_☉ to 0.63 M_☉ and the total mass range of the system is 1.3 M_☉ to 2.0 M_☉. It is very likely that the total mass exceeds the Chandrasekhar limit. Hence KPD1930+2752 is a candidate for a progenitor of a Type Ia supernova. According to the derived limits for the inclination angle, eclipses are likely to occur.