primarily on the specific angular momentum of the gas and the binary’s mass ratio (see also [@Artymowicz83; @Bate97]). Generally, accretion of gas with low specific angular momentum decreases the mass ratio and separation of the binary, while accretion of gas with high specific angular momentum increases the separation and drives the mass ratio toward unity. From these results, they predicted that closer binaries should have mass ratios that are biased toward equal masses compared to wider systems, since the gas which falls on to a closer system is likely to have more specific angular momentum, relative to the binary, than for a wider system.

They also studied the process of disc formation around an accreting protobinary system and found that for each protostar, a circumstellar disc was only formed if the specific angular momentum of the infalling gas was greater than the specific orbital angular momentum of that protostar about the centre of mass of the binary (Figure \[bate.accretion\]). This is because, to be capture by one of the protostars, the gas much achieve the same specific orbital angular momentum as that of the protostar. If the gas has more specific angular momentum initially, some of its angular momentum goes 