Historical light curve of GRO J1744–28 as observed by XMM-Newton (black points) and Chandra (blue points for HRC and red for ACIS-S cameras). Here, the bolometric luminosity estimated, assuming a distance to the source of 8 kpc and a bolometric correction factor of 3.7, is also indicated. The shaded area indicates the 2014 outburst of the source. The dotted line indicates the propeller luminosity estimated in this work.