$\textit{Siriusly}$, a newly identified intermediate-age Milky Way
  stellar cluster: A spectroscopic study of $\textit{Gaia}$ 1
  We confirm the reality of the recently discovered Milky Way stellar cluster
$\textit{Gaia}$ 1 using spectra acquired with the HERMES and AAOmega
spectrographs of the Anglo-Australian Telescope. This cluster had been
previously undiscovered due to its close angular proximity to Sirius, the
brightest star in the sky at visual wavelengths. Our observations identified 41
cluster members, and yielded an overall metallicity of [Fe/H]$=-0.13\pm0.13$
and barycentric radial velocity of $v_r=58.30\pm0.22$ km/s. These kinematics
provide a dynamical mass estimate of $12.9^{+4.6}_{-3.9}\times10^3$
M$_{\odot}$. Isochrone fits to $\textit{Gaia}$, 2MASS, and Pan-STARRS1
photometry indicate that $\textit{Gaia}$ 1 is an intermediate age ($\sim3$ Gyr)
stellar cluster. Combining the spatial and kinematic data we calculate
$\textit{Gaia}$ 1 has a circular orbit with a radius of about 12~kpc, but with
a large out of plane motion: $z_\textrm{max}=1.1^{+0.4}_{-0.3}$ kpc. Clusters
with such orbits are unlikely to survive long due to the number of plane
passages they would experience.
