Detection of solar-like oscillations in the G5 subgiant mu-Herculis
Abstract
A clear detection of excess of power, providing a substantial evidence for solar-like oscillations in the G5 subgiant μher, is presented. This star was observed over seven nights with the SARG echelle spectrograph operating with the 3.6-m Italian TNG Telescope, using an iodine absorption cell as a velocity reference. A clear excess of power centered at 1.2 mHz, with peak amplitudes of about 0.9 in the amplitude spectrum is present. Fitting the asymptotic relation to the power spectrum, a mode identification for the =0,1,2,3 modes in the frequency range 900-1600 μHz is derived. The most likely value for the large separation turns out to be 56.5 μHz, consistent with theoretical expectations. The mean amplitude per mode (l=0,1) at peak power results to be 0.63 m s-1, almost three times larger than the solar one.