is tempting to argue that the two stars could have been formed in the same star-forming event, but their proper motions and 3D velocities are required to confirm the similarity in the kinematics and to further investigate their possible association.

In contrast, the velocity $V_{\rm LSR}$ of [GCC-a]{} (127 ${{\mathrm{km~s}^{-1}}}$), is larger than the expected velocities for $x_2$ orbits ($< 80 {{\mathrm{km~s}^{-1}}}$) at its projected distance of 30 pc from Sgr A$^*$. The $x_2$ orbits depend on the mass distribution within the NSD, which is dominated by stars rather than the central supermassive black hole, except at the very center [@Launhardt-2002]. The mass enclosed within a circular orbit of a radius 30 pc and velocity of $130~{{\mathrm{km~s}^{-1}}}$ is $2.5\times 10^8~{\rm M_\odot}$, more than twice that predicted by the mass distribution constructed from infrared photometric data [@Bissantz-2002; @Launhardt-2002]. The kinematics of OH/IR stars and SiO masers are consistent with the smaller mass [@Lindqvist-1992; @Deguchi-2004]. On the other hand, the location and velocity of [GCC-a]{} approximates those of the Arches and Quintuplet clusters, although the two clusters, $\sim 4$ Myr, are much younger than GCC-a, $\sim 25$ Myr. The radial velocities of these clusters, plotted in Figure \[fig:LV\], are taken from @Figer-2002 