Posterior distribution of the parameters of the HerBS-89a lensed source, as obtained by the lens modeling and MCMC runs (see Sect. 5 for details). The constraints are given on the following parameters: the position (ΔRA and ΔDec in arcsec), the Einstein radius (b), the ellipticity (e), the scale radius (R_s), the position angle (θ_e) with the orientation measured east of north and the Sérsic index (n). See Fig. A.1 for further details.