Our recent studies of axial-symmetry breaking in the nearby ( d < 3 { kpc } ) star counts are sensitive to the distortions of stellar orbits perpendicular and parallel to the orientation of the bar just within and beyond the outer Lindblad resonance ( OLR ) radius .
Using the location of the sign flip in the left-right asymmetry in stars counts about the anticenter line to determine the OLR radius R _ { OLR } , and treating the bar as if it were a weakly non-axisymmetric effect , we use R _ { OLR } and recent measurements of the Galactic rotation curve and the Sun–Galactic-center distance R _ { 0 } to determine the pattern speed \Omega _ { p } of the Galactic bar , as well as the Galactic corotation radius R _ { CR } .
After removing the effect of the Large and Small Magellanic clouds from our asymmetry measurement , we find that R _ { OLR } = ( 0.96 \pm 0.03 ) R _ { 0 } = 7.85 \pm 0.25 kpc , \Omega _ { p } = 49.3 \pm 2.2 km s ^ { -1 } kpc ^ { -1 } , R _ { CR } = ( 0.58 \pm 0.04 ) R _ { 0 } = 4.76 \pm 0.27 kpc , revealing , as we shall show , that the Milky Way ’ s bar is likely both weak and fast , though we also note possible evidence for non-steady-state effects in the bar region .