The planet search program at the ESO Coude Echelle spectrometer - II. The alpha Centauri system: Limits for planetary companions

In this article we present the results of the planet search program carried out at the ESO Coude Echelle Spectrometer (CES) for components A and B of the alpha Centauri system. Since November 1992 we have obtained high precis ion differential radial velocities (RVs) for both stars. We demonstrate tha t, after subtraction of the binary orbital motion, no additional residual R V signal is present within our detection limits, which could have been attr ibuted to giant planets orbiting either of the two stars. We performed nume rical simulations to determine the detection threshold of the CES survey fo r planets around both stars. In combination with known dynamical limitation s for stable planetary orbits (Wiegert & Holman 1997) we can now set strong constraints on the existence of Jupiter-mass-type planets in the alpha Cen tauri system.