Radial velocity curves for 15 bright subdwarf B binary systems have been measured using high precision radial velocity measurements from high S/N optical high-resolution spectra .
In addition , two bright sdB stars are discovered to be radial velocity variable but the period could not yet be determined .
The companions for all systems are unseen .
The periods range from about 0.18 days up to more than ten days .
The radial velocity semi amplitudes are found to lie between 15 and 130 { km s ^ { -1 } } .
Using the mass functions , the masses of the unseen companions have been constrained to lower limits of 0.03 up to 0.55 { M } _ { \sun } , and most probable values of 0.03 up to 0.81 { M } _ { \sun } .
The invisible companions for three of our program stars are undoubtedly white dwarfs .
In the other cases they could be either white dwarfs or main sequence stars .
For two stars the secondaries could possibly be brown dwarfs .
As expected , the orbits are circular for most of the systems .
However , for one third of the program stars we find slightly eccentric orbits with small eccentricities of \epsilon \approx 0.02 –0.06 .
This is the first time that non-circular orbits have been found in sdB binaries .
No correlation with the orbital period can be found .