KIC 4768731: a bright long-period roAp star in the Kepler field

We report the identification of 61.45 d(-1) (711.2 mu Hz) oscillations, with amplitudes of 62.6 mu mag, in KIC 4768731 (HD 225914) using Kepler photometry. This relatively bright (V = 9.17) chemically peculiar star with spectral type A5 Vp SrCr(Eu) has previously been found to exhibit rotational modulation with a period of 5.21 d. Fourier analysis reveals a simple dipole pulsator with an amplitude that has remained stable over a 4-yr time span, but with a frequency that is variable. Analysis of high-resolution spectra yields stellar parameters of T-eff = 8100 +/- 200 K, log g=4.0 +/- 0.2, [Fe/H]=+0.31 +/- 0.24 and v sin i = 14.8 +/- 1.6 km s(-1). Line profile variations caused by rotation are also evident. Lines of Sr, Cr, Eu, Mg and Si are strongest when the star is brightest, while Y and Ba vary in antiphase with the other elements. The abundances of rare earth elements are only modestly enhanced compared to other roAp stars of similar T-eff and log g. Radial velocities in the literature suggest a significant change over the past 30 yr, but the radial velocities presented here show no significant change over a period of 4 yr.