Schematic representation of the spine fitting. The light circles show the location of the maxima after a high-order polynomial fit of the minor-axis profiles. The solid lines represent the final spines after fitting the maxima by a polynomial of order 2. The diamond represent the locations where the flux reaches 10% with respect to the maximum of the spine, and the squares are the center of the spine (i.e., the mid-point of these two points). The lateral asymmetry is the ratio between the distance of the centers to averaged disk size.