Template RR Lyrae H alpha, H beta, and H gamma Velocity Curves
  We present template radial velocity curves of $ab$-type RR Lyrae stars
constructed from high-precision measurements of ${\rm H\alpha}$, ${\rm
H\beta}$, and ${\rm H\gamma}$ lines. Amplitude correlations between the Balmer
line velocity curves, Johnson $V$-band, and SDSS $g$- and $r$-band light curves
are also derived. Compared to previous methods, these templates and derived
correlations reduce the uncertainty in measured systemic (center-of-mass)
velocities of RR Lyrae stars by up to 15 {\kms}, and will be of particular
interest to wide-area spectroscopic surveys such as the Sloan Digital Sky
Survey (SDSS) and LAMOST Experiment for Galactic Understanding and Exploration
(LEGUE).
