2006ApJ...636..979I

Observations of Galactic and extragalactic globular clusters have shown that, on average, metal-rich clusters are ∼3 times more likely to contain a bright X-ray source than their metal-poor counterparts. We propose that this can be explained by taking into account the difference in the stellar structure of main-sequence donors with masses between ∼0.85 and ∼1.25M_☉at different metallicities. Metal-poor main-sequence stars in this mass range do not have an outer convective zone, while metal-rich stars do. The absence of this zone turns off magnetic braking, a powerful mechanism of orbital shrinkage, leading to the failure of dynamically formed main-sequence-neutron star binaries to start mass transfer or appear as bright, low-mass X-ray binaries.