Sensitivity curves for α as a function of the ULDM mass m for the system J1903+0327 (with parameters given in Table E.2) for masses near the resonant one at ω_b = m. Solid lines are obtained after marginalising over all the three nuisance parameters Ξ_i (i = 0, 1, 2) in the model of Θ′ (we use uniform priors for all of them), dashed lines are obtained after marginalising only over the parameters Ξ₀ and Ξ₁ (which correspond to a linear growth coefficient and a constant error in Θ′) while the coefficient Ξ₂ (which gives a quadratic growth) is assumed to be known and subtracted so that Ξ₂ = 0