2023ApJ...950...27G

Magnetic braking has a prominent role in driving the evolution of close low-mass binary systems and heavily influences the rotation rates of low-mass F- and later-type stars with convective envelopes. Several possible prescriptions that describe magnetic braking in the context of 1D stellar evolution models currently exist. We test four magnetic braking prescriptions against both low-mass X-ray binary orbital periods from the Milky Way and single-star rotation periods observed in open clusters. We find that the data favor a magnetic braking prescription that follows a rapid transition from fast to slow rotation rates, exhibits saturated (inefficient) magnetic braking below a critical Rossby number, and that is sufficiently strong to reproduce ultra-compact X-ray binary systems. Of the four prescriptions tested, these conditions are satisfied by a braking prescription that incorporates the effect of high-order magnetic field topology on angular momentum loss. None of the braking prescriptions tested are able to replicate the stalled spin down observed in open cluster stars aged 700-1000 Myr or so, with masses ≲0.8 M_⊙.