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Published online by Cambridge University Press: 12 April 2016
Recently several interesting results concerning the time dependence of solar p-mode frequencies have appeared. In particular it has been shown that the mode frequencies change with solar activity (Libbrecht and Woodard 1991).
We present preliminary results from an analysis of two ≈ 3 month observation runs with the Fourier Tachometer (which was operated by HAO and NSO) from 1987 and 1989. The analysis was done with two different methods in order to test for systematic errors. We show that the mode frequencies change in a manner similar to that reported by Libbrecht and Woodard. We also present results for the frequency splittings caused by the solar rotation.