Constraints on planets around β Pic with Harps radial velocity data

International audienceContext. The β Pictoris system with its debris disk and a massive giant planet orbiting at ≃9 AU represents an ideal laboratory for studying giant planet formation and evolution as well as planet-disk interactions. β Pic b can also help in testing brightness-mass relations at young ages. Other planets, yet undetected, may of course be present in the system. Aims: We aim at directly constraining the mass of β Pic b and at searching for additional jovian planets on orbits closer than typically 2 AU. Methods: We used high-precision Harps data collected over eight years since 2003 to measure and analyse β Pic radial velocities. Results: We show that the true mass of β Pic b is less than 10, 12, 15.5, 20, and 25 MJup if orbiting at 8, 9, 10, 11, and 12 AU, respectively. This is the first direct constraint on the mass of an imaged planet. The upper mass found is well in the range predicted by brightness-mass relations provided by current "hot start" models. We also exclude the presence of giant planets more massive than 2.5 MJup with periods less than 100 days (hot Jupiters), more massive than 9 MJup for periods in the range 100-500 days. In the 500-1000 day range, the detection limit is in the brown dwarf domain. Beyond the intrinsic interest for β Pic, these results show the possibilities of precise RV measurements of early-type, rapidly rotating stars. Based on observations collected at the European Southern Observatory, Chile, ESO.RV data is available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/542/A18