Mass function plotted against the orbital period for all the binary pulsars from the ATNF pulsar catalogue (https://www.atnf.csiro.au/research/pulsar/psrcat/) (Manchester et al. 2005). The binary pulsars in the Galactic field are shown with filled grey dots, while the pulsars in GC are circles. Pulsars in GC 47 Tuc are in red, and those in other GCs are shown with black circles. The inclined dotted yellow lines represent the constant projected semi-major axis of the binary orbit, which is smallest at the lower-left side: x = 1 lt-millisecond. From the bottom left to the top right, the successive dotted yellow lines are an order of magnitude greater than the previous one. The magenta coloured star symbol represents the 47 Tuc ai system.