  Among the tens of thousands of known RR Lyrae stars there are only a handful
that show indications of possible binarity. The question why this is the case
is still unsolved, and has recently sparked several studies dedicated to the
search for additional RR Lyraes in binary systems. Such systems are
particularly valuable because they might allow to constrain the stellar mass.
Most of the recent studies, however, are based on photometry by finding a light
time effect in the timings of maximum light. This approach is a very promising
and successful one, but it has a major drawback: by itself, it cannot serve as
a definite proof of binarity, because other phenomena such as the Blazhko
effect or intrinsic period changes could lead to similar results. Spectroscopic
radial velocity measurements, on the other hand, can serve as definite proof of
binarity. We have therefore started a project to study spectroscopically RR
Lyrae stars that are suspected to be binaries. We have obtained radial velocity
(RV) curves with the 2.1m telescope at McDonald observatory. From these we
derive systemic RVs which we will compare to previous measurements in order to
find changes induced by orbital motions. We also construct templates of the RV
curves that can facilitate future studies. We also observed the most promising
RR Lyrae binary candidate, TU UMa, as no recent spectroscopic measurements were
available. We present a densely covered pulsational RV curve, which will be
used to test the predictions of the orbit models that are based on the O-C
variations.
