Upper limit for the Alfvénic Mach number of the stellar wind at the orbit of GJ 625 b as a function of the average large-scale surface magnetic field strength of the host star. The gray shaded regions show where the field strength is outside the likely estimate of the magnetic field of the star from 17 to 189 G, estimated from empirical relationships. For average field strengths ≳20 G, we estimate that the planet must orbit inside the Alfvén surface, corresponding to a Mach number <1 (indicated by the dashed horizontal line). In this region (highlighted in blue), magnetic star-planet interactions can occur. However, 3D MHD simulations are needed to assess these prospects further.