Kinematic Peculiarities of Gould Belt Stars

Abstract

We analyzed the space velocities of Gould Belt stars younger than 125 Myr located at heliocentric distances <650 pc. We determined the rotation and expansion parameters of the Gould Belt by assuming the existence of a single kinematic center whose direction was found to be the following: $l_\circ=128^\circ$ and $R_\circ=150$ pc. The linear velocities reach their maximum at a distance of $\approx300$ pc from the center and are -6 km s$^{-1}$ for the rotation (whose direction coincides with the Galactic rotation) and +4 km s$^{-1}$ for the expansion. The stellar rotation model used here is shown to give a more faithful description of the observed velocity field than the linear model based on the Oort constants $A_G$ and $B_G$. We present evidence that the young clusters $\beta$ Pic, Tuc/HorA, and TWA belong to the Gould Belt structure.