Propeller spin-down rate for LSI, ﹩\dot{\nu }﹩, calculated with the torque (Equation (10)), as a function of the polar field, B _p /10¹² G. Each of the two shaded bands corresponds to an ﹩\dot{M}﹩ range varying from ﹩\dot{M}={10}^{-2}﹩ (leftmost dashed curves) to ﹩{10}^{-4}{\dot{M}}_{{\rm{E}}{\rm{d}}{\rm{d}}}﹩ (rightmost solid curves). The former (latter) value corresponds to the estimated quiescent L _X luminosity of LSI at periastron (apastron). The left (right) band corresponds to ξ = 0.1 (ξ = 1). The horizontal band marks the maximum spin-down rate of LSI, viz. ﹩-6.04\lt \dot{\nu }/{10}^{-9}{{\rm{s}}}^{-2}\,\lt -4.39﹩ (Weng et al. 2022).