Mass ratio, the hills mechanism, and the Galactic Centre S-stars

The Galactic Centre contains several young populations within its central parsec: a disc between ~0.05 and 0.5 pc from the centre, and the isotropic S-star cluster extending an order of magnitude further inwards in radius. Recent observations (i.e. spectroscopy and hypervelocity stars) suggest that some S-stars originate in the disc. In particular, the S-stars may be remnants of tidally disrupted disc binaries. However, there is an apparent inconsistency in this scenario: the disc contains massive O and Wolf-Rayet stars while the S-stars are lower mass, B stars. We explore two different explanations for this apparent discrepancy: (i) a built-in bias in binary disruptions, where the primary star remains closer in energy to the centre-of-mass orbit than the secondary and (ii) selective tidal disruption of massive stars within the S-star cluster. The first explanation is plausible. On the other hand, tidal disruptions have not strongly affected the mass distribution of the S-stars over the last several Myr.