  A detailed analysis is presented of 33 RR Lyrae stars in Pisces observed with
the Kepler space telescope over the 8.9-day long K2 Two-Wheel Concept
Engineering Test. The sample includes not only fundamental-mode and first
overtone (RRab and RRc) stars but the first two double-mode (RRd) stars that
Kepler detected and the only modulated first-overtone star ever observed from
space so far. The precision of the extracted K2 light curves made it possible
to detect low-amplitude additional modes in all subtypes. All RRd and
non-modulated RRc stars show the additional mode at P_X/P_1~0.61 that was
detected in previous space-based photometric measurements. A periodicity longer
than the fundamental mode was tentatively identified in one RRab star that
might belong to a gravity mode. We determined the photometric [Fe/H] values for
all fundamental-mode stars and provide the preliminary results of our efforts
to fit the double-mode stars with non-linear hydrodynamic pulsation models. The
results from this short test run indicate that the K2 mission will be, and has
started to be, an ideal tool to expand our knowledge about RR Lyrae stars. As a
by-product of the target search and analysis, we identified 165 bona-fide
double-mode RR Lyrae stars from the Catalina Sky Survey observations throughout
the sky, 130 of which are new discoveries.
