The Milky Way's circular velocity curve and its constraint on the
  Galactic mass with RR Lyrae stars
  We present a sample of 1148 ab-type RR Lyrae (RRLab) variables identified
from Catalina Surveys Data Release 1, combined with SDSS DR8 and LAMOST DR4
spectral data. We firstly use a large sample of 860 Galactic halo RRLab stars
and derive the circular velocity distributions for the stellar halo. With the
precise distances and carefully determined radial velocities (the
center-of-mass radial velocities) by considering the pulsation of the RRLab
stars in our sample, we can obtain a reliable and comparable stellar halo
circular velocity curve. We take two different prescriptions for the velocity
anisotropy parameter {\beta} in the Jeans equation to study the circular
velocity curve and mass profile. We test two different solar peculiar motions
in our calculation. Our best result with the adopted solar peculiar motion 1 of
(U, V, W) = (11.1, 12, 7.2) km/s is that the enclosed mass of the Milky Way
within 50 kpc is (3.75 +/- 1.33) *10^11Msun based on \beta = 0 and the circular
velocity 180 +/- 31.92 (km/s) at 50 kpc. This result is consistent with
dynamical model results, and it is also comparable to the previous similar
works.
