Left panel: Fit of a gravitational arc. Three characteristic points have been identified on the image (CP1-3), through which a circular segment (CP2-CP3) has been traced. The curvature radius (Rc) and the center of curvature (CC) of the circular segment define the radius and the center of the arc. Right panel: Transversal width profile of the arc in the left panel (red solid line). The blue dotted line shows an interpolation of the profile with a Bezier curve. The horizontal lines correspond to various determinations of the arc width. Figures from
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