FSR 1716: A new Milky Way Globular Cluster confirmed using VVV RR Lyrae
  stars
  We use deep multi-epoch near-IR images of the VISTA Variables in the V\'ia
L\'actea (VVV) Survey to search for RR Lyrae stars towards the Southern
Galactic plane. Here we report the discovery of a group of RR Lyrae stars close
together in VVV tile d025. Inspection of the VVV images and PSF photometry
reveals that most of these stars are likely to belong to a globular cluster,
that matches the position of the previously known star cluster FSR\,1716. The
stellar density map of the field yields a $>100$ sigma detection for this
candidate globular cluster, that is centered at equatorial coordinates
$RA_{J2000}=$16:10:30.0, $DEC_{J2000}=-$53:44:56; and galactic coordinates
$l=$329.77812, $b=-$1.59227. The color-magnitude diagram of this object reveals
a well populated red giant branch, with a prominent red clump at $K_s=13.35 \pm
0.05$, and $J-K_s=1.30 \pm 0.05$. We present the cluster RR Lyrae positions,
magnitudes, colors, periods and amplitudes. The presence of RR Lyrae indicates
an old globular cluster, with age $>10$ Gyr. We classify this object as an
Oosterhoff type I globular cluster, based on the mean period of its RR Lyrae
type ab, $<P>=0.540$ days, and argue that this is a relatively metal-poor
cluster with $[Fe/H] = -1.5 \pm 0.4$ dex. The mean extinction and reddening for
this cluster are $A_{K_s}=0.38 \pm 0.02$, and $E(J-K_s)=0.72 \pm 0.02$ mag,
respectively, as measured from the RR Lyrae colors and the near-IR
color-magnitude diagram. We also measure the cluster distance using the RR
Lyrae type ab stars. The cluster mean distance modulus is $(m-M)_0 = 14.38 \pm
0.03$ mag, implying a distance $D = 7.5 \pm 0.2$ kpc, and a Galactocentric
distance $R_G=4.3$ kpc.
