* Astronomy

Title: A search for solar-like oscillations in K giants in the globular cluster M4
Authors: S. Frandsen, H. Bruntt, F. Grundahl, G. Kopacki, H. Kjeldsen, T. Arentoft, D. Stello, T. R. Bedding, A. P. Jacob, R. L. Gilliland, P. D. Edmonds, E. Michel, J. Matthiesen

To expand the range in the colour-magnitude diagram where asteroseismology can be applied, we organized a photometry campaign to find evidence for solar-like oscillations in giant stars in the globular cluster M4. The aim was to detect the comb-like p-mode structure characteristic for solar-like oscillations in the amplitude spectra. The two dozen main target stars are in the region of the bump stars and have luminosities in the range 50-140 Lsun. We collected 6160 CCD frames and light curves for about 14000 stars were extracted. We obtain high quality light curves for the K giants, but no clear oscillation signal is detected. High precision differential photometry is possible even in very crowded regions like the core of M4. Solar-like oscillations are probably present in K giants, but the amplitudes are lower than classical scaling laws predict.

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