Constraints on the orbital inclination and masses of the J1618−3921 binary. The dashed red lines correspond to constraints derived from the TEMPONEST fit for the rate of advance of periastron $\dot{\omega }$ presented in Table 3 assuming the validity of GR and regarding the effect as purely relativistic. The black lines include 68.3 and 95.4% of all probability of the 2-dimensional probability distribution functions (pdfs) derived from the χ² map. The left of the two inner plots shows the M_c-cosι diagram, that was sampled evenly. The grey area is excluded because M_PSR must be positive. The plot to its right shows the projection of the M_c-cosι pdf on the M_PSR-M_c space using the mass function. The grey area is excluded because sinι ≤ 1. The outer three plots display the projected distributions for cosι, M_PSR, and M_c. the hatched area corresponds to the 1σ intervals. The unconstrained inclination angle shows that we have a non-detection of the Shapiro delay; thus, we do not provide the confidence intervals.