Gaia RR Lyrae Stars in Nearby Ultra-Faint Dwarf Satellite Galaxies
  We search for RR Lyrae stars in 27 nearby ($<100$ kpc) ultra-faint dwarf
satellite galaxies using the Gaia DR2 catalog of RR Lyrae stars. Based on
proper motions, magnitudes and location on the sky, we associate 47 Gaia RR
Lyrae stars to 14 different satellites. Distances based on RR Lyrae stars are
provided for those galaxies. We have identified RR Lyrae stars for the first
time in the Tucana II dwarf galaxy, and find additional members in Ursa Major
II, Coma Berenices, Hydrus I, Bootes I and Bootes III. In addition we have
identified candidate extra-tidal RR Lyrae stars in six galaxies which suggest
they may be undergoing tidal disruption. We found 10 galaxies have no RR Lyrae
stars neither in Gaia nor in the literature. However, given the known
completeness of Gaia DR2 we cannot conclude these galaxies indeed lack variable
stars of this type.
