Measurements of HD 40307

The HARPS radial velocity measurements of HD 40307 are folded with the orbital periods of the three discovered planets: 4.3, 9.6, and 20.4 days, respectively. In each case, the contribution of the two other planets has been subtracted. The solid line shows the best fit to the measurements, corresponding to minimum masses of 4.2, 6.7, and 9.4 Earth masses. Note that the full span of the vertical axis is only 10 m/s! Error bars indicate the accuracy of the measurements.