A search of very low amplitude magnetoacoustic pulsations with HARPS
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We have obtained time-resolved spectroscopic observations for a sample of 10 cool Ap stars using the ultra-stable spectrograph HARPS at the ESO 3.6-m telescope. The aim of our study was to search for low-amplitude oscillations in Ap stars with no or inconclusive evidence of pulsational variability. Here we report initial results of our investigation. We confirm the presence of ~16-min period pulsations in beta CrB (HD 137909) and demonstrate multiperiodic character of oscillations in this star. Furthermore, we discovered very low amplitude 9-min pulsations in HD 75445 - an object spectroscopically very similar to known roAp stars.
submitted to Contrib. Astron. Obs. Skalnate Pleso (Proceedings of the CP#Ap Workshop, Vienna, 2007, eds. J. Ziznovsky, J. Zverko, E. Pauntzen, M. Netopil)
submitted to Contrib. Astron. Obs. Skalnate Pleso (Proceedings of the CP#Ap Workshop, Vienna, 2007, eds. J. Ziznovsky, J. Zverko, E. Pauntzen, M. Netopil)