Using multi–epoch VLA observations , covering a time baseline of 29.1 years , we have measured the proper motions of 88 young stars with compact radio emission in the core of the Orion Nebula Cluster ( ONC ) and the neighboring BN/KL region .
Our work increases the number of young stars with measured proper motion at radio frequencies by a factor of 2.5 and enables us to perform a better statistical analysis of the kinematics of the region than was previously possible .
Most stars ( 79 out of 88 ) have proper motions consistent with a Gaussian distribution centered on \overline { \mu _ { \alpha } \cos { \delta } } = 1.07 \pm 0.09 { mas yr ^ { -1 } } , and \overline { \mu _ { \delta } } = -0.84 \pm 0.16 { mas yr ^ { -1 } } , with velocity dispersions of \sigma _ { \alpha } = 1.08 \pm 0.07 { mas yr ^ { -1 } } , \sigma _ { \delta } = 1.27 \pm 0.15 { mas yr ^ { -1 } } .
We looked for organized movements of these stars but found no clear indication of radial expansion/contraction or rotation .
The remaining nine stars in our sample show peculiar proper motions that differ from the mean proper motions of the ONC by more than 3 \sigma .
One of these stars , V 1326 Ori , could have been expelled from the Orion Trapezium 7,000 years ago .
Two could be related to the multi-stellar disintegration in the BN/KL region , in addition to the previously known sources BN , I and n. The others either have high uncertainties ( so their anomalous proper motions are not firmly established ) or could be foreground objects .