Frequency analysis of the rapidly oscillating Ap star HR 1217(HD 24712)

Abstract

High speed photometric observations of HR 1217 have been obtained during 119 hr on 18 nights in 1981. On five of those nights contemporaneous observations were obtained at the South African Astronomical Observatory and Cerro Tololo Inter-American Observatory which greatly reduce the severe daily aliasing problem in the frequency analysis of this star. A frequency analysis of three nights of data at the phase of pulsation amplitude maximum reveals six nearly uniformly spaced frequencies which we suggest are associated with six consecutive overtones of pulsation. From the frequency ratios we estimate the overtones of the pulsations to be 76 to 81. Pulsation amplitude maximum coincides with magnetic maximum again for these data which, with previous data obtained in 1980 for this star, sets an upper limit of C_{k, l} ≼ 0.002 at the 3 σ level of confidence.