Orbital variability of intrinsic PD P_int and PA θ_int of LS I +61° 303 in V band. The filled blue squares with 1σ errors correspond to the average values of the individual observations (represented by gray circles with error bars) and the standard errors of the mean calculated within the phase bins of width Δϕ = 0.091. The vertical dashed lines correspond to the phases of periastron (ϕ = 0.275) and apastron (ϕ = 0.775) as derived by Aragona et al. (2009).