We use the multi-epoch radial velocities acquired by the APOGEE survey to perform a large scale statistical study of stellar multiplicity for field stars in the Milky Way , spanning the evolutionary phases between the main sequence and the red clump .
We show that the distribution of maximum radial velocity shifts ( \Delta RV _ { max } ) for APOGEE targets is a strong function of \log g , with main sequence stars showing \Delta RV _ { max } as high as \sim 300 km s ^ { -1 } , and steadily dropping down to \sim 30 km s ^ { -1 } for \log g \sim 0 , as stars climb up the Red Giant Branch ( RGB ) .
Red clump stars show a distribution of \Delta RV _ { max } values comparable to that of stars at the tip of the RGB , implying they have similar multiplicity characteristics .
The observed attrition of high \Delta RV _ { max } systems in the RGB is consistent with a lognormal period distribution in the main sequence and a multiplicity fraction of 0.35 , which is truncated at an increasing period as stars become physically larger and undergo mass transfer after Roche Lobe Overflow during H shell burning .
The \Delta RV _ { max } distributions also show that the multiplicity characteristics of field stars are metallicity dependent , with metal-poor ( [ Fe/H ] \lesssim - 0.5 ) stars having a multiplicity fraction a factor 2-3 higher than metal-rich ( [ Fe/H ] \gtrsim 0.0 ) stars .
This has profound implications for the formation rates of interacting binaries observed by astronomical transient surveys and gravitational wave detectors , as well as the habitability of circumbinary planets .