Ultra-high-precision velocity measurements of oscillations in alpha Centauri A

We have made differential radial velocity measurements of the star a Centauri A using two spectrographs, the UV-Visual Echelle Spectrograph (UVES) and the University College London Echelle Spectrograph (UCLES), both with iodine absorption cells for wavelength referencing. Stellar oscillations are clearly visible in the time series. After removing jumps and slow trends in the data, we show that the precision of the velocity measurements per minute of observing time is 0.42 m s(-1) for UVES and 1.0 m s(-1) for UCLES, while the noise level in the Fourier spectrum of the combined data is 1.9 cm s(-1). As such, these observations represent the most precise velocities ever measured on any star apart from the Sun.