Combined constraints of the location (astrometry) of the July 22 flare in the R/Rg – inclination plane, from fits with the NERO code (Bauböck et al., in prep. but also Yang & Wang 2014; Dexter & Agol 2009). For R ≥ 6 Rg we use a = 0, and for R < 6 Rg, a = 1. The three astrometry contours represent the 1-, 2- and 3-σ constraints from the model fitting, with the dark blue being the most favoured. Since we do not have any prior knowledge of the inclination of the orbit, we have weighted the probabilities by sin(i) to account for the geometric bias. The polarization measurement of July 28 with a period of Ppol = 48 ± 6 min yields the right-hatched vertical constraint. The requirement of a Doppler boost (“contrast”) <2.5 is given by the green area, with a lower contrast pushing further down. The presence of a single and full loop in the polarization data yields the left-hatched, mostly left-right constraint. The combined constraints favour R = 7.6 ± 0.5 Rg and inclination i 30 degrees (black encircled area).