Fit of the eccentric SMBH binary model (solid) and a model with fixed environmental parameters (ƒ_ref = 30nHz, α = 8/3,β = 5/8) with added eccentricity (dashed). Note that the confidence levels are shown for each fit separately, with the ratio between the 1σ contours of the purely eccentric and environmental+eccentricity model being ≈5. The black circle denotes the best-fit point in the model including eccentricities, while the black square/star indicate the best-fit points for circular binaries with environmental effects omitted/included.