* Astronomy

Title: KIC 4768731: a bright long-period roAp star in the Kepler Field
Author: B. Smalley, E. Niemczura, S.J. Murphy, H. Lehmann, D.W. Kurtz, D.L. Holdsworth, M.S. Cunha, L.A. Balona, M. Briquet, H. Bruntt, P. de Cat, P. Lampens, A.O. Thygesen, K. Uytterhoeven

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. 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 anti-phase 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.

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