Nineteen of the \sim 40 RR Lyrae stars in the Kepler field have been identified as candidate non-Blazhko ( or unmodulated ) stars .
In this paper we present the results of Fourier decomposition of the time-series photometry of these stars acquired during the first 417 days of operation ( Q0-Q5 ) of the Kepler telescope .
Fourier parameters based on \sim 18400 long-cadence observations per star ( and \sim 150000 short-cadence observations for FN Lyr and for AW Dra ) are derived .
None of the stars shows the recently discovered ‘ period-doubling ’ effect seen in Blazhko variables ; however , KIC 7021124 has been found to pulsate simultaneously in the fundamental and second overtone modes with a period ratio P _ { 2 } / P _ { 0 } \sim 0.59305 and is similar to the double-mode star V350 Lyr .
Period change rates are derived from O - C diagrams spanning , in some cases , over 100 years ; these are compared with high-precision periods derived from the Kepler data alone .
Extant Fourier correlations by Kovács , Jurcsik et al . ( with minor transformations from the V to the Kp passband ) have been used to derive underlying physical characteristics for all the stars .
This procedure seems to be validated through comparisons of the Kepler variables with galactic and LMC RR Lyrae stars .
The most metal-poor star in the sample is NR Lyr , with [ Fe/H ] = -2.3 dex ; and the four most metal-rich stars have [ Fe/H ] ranging from -0.6 to +0.1 dex .
Pulsational luminosities and masses are found to be systematically smaller than L and { \cal M } values derived from stellar evolution models , and are favoured over the evolutionary values when periods are computed with the Warsaw linear hydrodynamics code .
Finally , the Fourier parameters are compared with theoretical values derived using the Warsaw non-linear convective pulsation code .