Apex and Kinematical Structure of Castor and Ursa Major Moving Stellar Groups

Based on space velocity components UVW and using a recent dataset for Castor and Ursa Major moving groups, we compute the apex position with two methods. Classical convergent procedures give ( A cp , D cp ) = (80 7830, –17 2598; Castor, 298 334, –34 6405; UMa) for Castor and Ursa Major groups. According to the AD-map method we deduce the apex position ( A 0 , D 0 ) = (79 5514, –17 3948; Castor, 304 767, ‒35 2045; UMa) for these two objects. These results are in good agreement with other published coordinated. Also, we calculate all parameters with a model of stream velocity ellipsoidal motions, which reveals inner kinematical structure. Finally, we consider the intrinsic variations considered with late-type moving groups (streams) for the longitude of the vertex versus temperature (spectral types).