Context : We recently reported on the detection of a possible planetary-mass companion to $ β $ ~Pictoris at a projected separation of 8 au from the star , using data taken in November 2003 with NaCo , the adaptive-optics system installed on the Very Large Telescope UT4 .
Eventhough no second epoch detection was available , there are strong arguments to favor a gravitationally bound companion rather than a background object .
If confirmed and located at a physical separation of 8 au , this young , hot ( \sim 1500 K ) , massive Jovian companion ( \sim 8 M _ { Jup } ) would be the closest planet to its star ever imaged , could be formed via core-accretion , and could explain the main morphological and dynamical properties of the dust disk .

Aims : Our goal was to return to \beta Pic five years later to obtain a second-epoch observation of the companion or , in case of a non-detection , constrain its orbit .

Methods : Deep adaptive-optics L ^ { \prime } -band direct images of \beta Pic and K _ { s } -band Four-Quadrant-Phase-Mask ( 4QPM ) coronagraph images were recorded with NaCo in January and February 2009 .
We also use 4QPM data taken in November 2004 .

Results : No point-like signal with the brightness of the companion candidate ( apparent magnitudes L ^ { \prime } = 11.2 or K _ { s } \simeq 12.5 ) is detected at projected distances down to \simeq 6.5 au from the star in the 2009 data .

Conclusions : As expected , the non-detection does not allow to rule out a background object ; however , we show that it is consistent with the orbital motion of a bound companion that got closer to the star since first observed in 2003 and that is just emerging from behind the star at the present epoch .
We place strong constraints on the possible orbits of the companion and discuss future observing prospects .