Solar-like oscillations in the K1 dwarf star α Cen B

The K1 dwarf α Cen B was observed with the Coralie spectrograph on the 1.2-m Swiss telescope at La Silla in April 2003. Thirteen nights of observations have made it possible to collect 3626 radial velocity measurements with a standard deviation of 1.4 m s-1 exhibiting a mean noise level in the amplitude spectrum of only 3.75 cm s-1. Twelve oscillation modes have been identified in the power spectrum between 3 and 4.6 mHz with amplitudes in the range 8.7 to 13.7 cm s-1 and showing a regularity with a large separation of 161.1 μHz. A preliminary discussion on the physical parameters of the α Cen binary system is presented.