The kinematics and zero-point of the log P-⟨MK⟩ relation for Galactic RR Lyrae variables via statistical parallax

We use accurate absolute proper motions and Two-Micron All-Sky Survey K-s-band apparent magnitudes for 364 Galactic RR Lyrae variables to determine the kinematical parameters of the Galactic RR Lyrae population and constrain the zero-point of the K-s-band period-luminosity relation for these stars via statistical parallax. We find the mean velocities of the halo-and thick-disc RR Lyrae populations in the solar neighbourhood to be [U-0(Halo), V-0(Halo), W-0(Halo)] = (-12 +/- 10, -217 +/- 9, -6 +/- 6) km s(-1) and [U-0(Disc), V-0(Disc), W-0(Disc)] = (-15 +/- 7, -44 +/- 7, -25 +/- 5) km s(-1), respectively, and the corresponding components of the velocity-dispersion ellipsoids, [sigma V-R(Halo), sigma V-theta(Halo), sigma W(Halo)] = (167 +/- 9, 86 +/- 6, 78 +/- 5) km s(-1) and [sigma V-R(Disc), sigma V-theta(Disc), sigma W(Disc)] = (55 +/- 7, 44 +/- 6, 30 +/- 4) km s(-1), respectively. The fraction of thick-disc stars is estimated at 0.25 +/- 0.03. The corrected infrared period-luminosity relation is < M-Ks > = -2.33 log P-F - 0.818 +/- 0.081, implying a Large Magellanic Cloud (LMC) distance modulus of 18.27 +/- 0.08 and a solar Galactocentric distance of 7.58 +/- 0.40 kpc. Our results suggest no or slightly prograde rotation for the population of halo RR Lyraes in the Milky Way.