Astrophys.J.614:380-385,2004 We analyse our recently-published velocity measurements of alpha Cen A
(Butler et al. 2004). After adjusting the weights on a night-by-night basis in
order to optimize ...the window function to minimize sidelobes, we extract 42
oscillation frequencies with l=0 to 3 and measure the large and small frequency
separations. We give fitted relations to these frequencies that can be compared
with theoretical models and conclude that the observed scatter about these fits
is due to the finite lifetimes of the oscillation modes. We estimate the mode
lifetimes to be 1-2 d, substantially shorter than in the Sun.
Astrophys.J.600:L75-L79,2003 We have made differential radial velocity measurements of the star alpha Cen
A using two spectrographs, UVES and 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
for UVES and 1.0 m/s for UCLES, while the noise level in the Fourier spectrum
of the combined data is 1.9 cm/s. As such, these observations represent the
most precise velocities ever measured on any star apart from the Sun.
We have made velocity observations of the star alpha Cen B from two sites, allowing us to identify 37 oscillation modes with l=0-3. Fitting to these modes gives the large and small frequency ...separations as a function of frequency. The mode lifetime, as measured from the scatter of the oscillation frequencies about a smooth trend, is similar to that in the Sun. Limited observations of the star delta Pav show oscillations centred at 2.3 mHz with peak amplitudes close to solar. We introduce a new method of measuring oscillation amplitudes from heavily-smoothed power density spectra, from which we estimated amplitudes for alpha Cen A and B, beta Hyi, delta Pav and the Sun. We point out that the oscillation amplitudes may depend on which spectral lines are used for the velocity measurements.
We analyse our recently-published velocity measurements of alpha Cen A (Butler et al. 2004). After adjusting the weights on a night-by-night basis in order to optimize the window function to minimize ...sidelobes, we extract 42 oscillation frequencies with l=0 to 3 and measure the large and small frequency separations. We give fitted relations to these frequencies that can be compared with theoretical models and conclude that the observed scatter about these fits is due to the finite lifetimes of the oscillation modes. We estimate the mode lifetimes to be 1-2 d, substantially shorter than in the Sun.
We have made differential radial velocity measurements of the star alpha Cen A using two spectrographs, UVES and 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 for UVES and 1.0 m/s for UCLES, while the noise level in the Fourier spectrum of the combined data is 1.9 cm/s. As such, these observations represent the most precise velocities ever measured on any star apart from the Sun.
