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 } = 35 500 \pm 500 ~ { } { K } , \log g = 5.56 \pm 0.05 and \log \frac { He } { H } = -1.48 \pm 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The radial velocity curve was measured and combined with all available published and unpublished radial velocity data in order to get results of high accuracy ( K = 341 \pm 1 ~ { } { km s ^ { -1 } } , P = 0.0950933 \pm 0.0000015 ~ { } { d } ) .
For the first time we measured the projected rotational velocity .
The preliminary result is v _ { rot } \sin { i } = 97 \pm 9 ~ { } { km s ^ { -1 } } ~ { } ( 3 \sigma ) .
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 _ { \odot } to 0.63 ~ { } M _ { \odot } and the total mass range of the system is 1.3 ~ { } M _ { \odot } to 2.0 ~ { } M _ { \odot } .
It is very likely that the total mass exceeds the Chandrasekhar limit .
Hence KPD 1930+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 .