Magnitude scatter measured for all the stars located within 20^′′ (gray dots) from the RB X-ray position as a function of their magnitude. The black circles highlight all the sources detected within a distance of just 1.5^′′ from the RB. The large red star marks the candidate optical counterpart. The top, middle, and bottom panels refer to the F606W, F814W, and Ks filters, respectively.