Context : Understanding the properties of young open clusters , such as the Initial Mass Function ( IMF ) , star formation history and dynamic evolution , is crucial to obtain reliable theoretical predictions of the mechanisms involved in the star formation process .

Aims : We want to obtain a list , as complete as possible , of confirmed members of the young open cluster \gamma Velorum , with the aim of deriving general cluster properties such as the IMF .

Methods : We used all available spectroscopic membership indicators within the Gaia-ESO public archive together with literature photometry and X-ray data and , for each method , we derived the most complete list of candidate cluster members .
Then , we considered photometry , gravity and radial velocities as necessary conditions to select a subsample of candidates whose membership was confirmed by using the lithium and H \alpha lines and X-rays as youth indicators .

Results : We found 242 confirmed and 4 possible cluster members for which we derived masses using very recent stellar evolutionary models .
The cluster IMF in the mass range investigated in this study shows a slope of \alpha = 2.6 \pm 0.5 for 0.5 < M / M _ { \odot } < 1.3 and \alpha = 1.1 \pm 0.4 for 0.16 < M / M _ { \odot } < 0.5 and is consistent with a standard IMF .

Conclusions : The similarity of the IMF of the young population around \gamma ^ { 2 } Vel to that in other star forming regions and the field suggests it may have formed through very similar processes .