Velocity variation of mu Arae observed by HARPS

Illustration of the high-quality radial velocity measurements obtained with HARPS. Here also, the solid line shows the best fit to the measurements, assuming the existence of two planets. The data were obtained over a time span of 80 days and the first points shown are the data from the 8 nights in June. Note that the full span of the vertical axis is only 40 m/s! Error bars indicate the accuracy of the measurements. The lower part of the diagram displays the deviation of the measurements from the best fit.