Binary stars and higher-order multiple systems are an ubiquitous outcome of star formation , especially as the system mass increases .
The companion mass-ratio distribution is a unique probe into the conditions of the collapsing cloud core and circumstellar disk ( s ) of the binary fragments .
Inside a \sim 1000 AU the disks from the two forming stars can interact , and additionally companions can form directly through disk fragmentation .
We should therefore expect the mass-ratio distribution of close companions ( a \lesssim 100 AU ) to differ from that of wide companions .
This prediction is difficult to test using traditional methods , especially with intermediate-mass primary stars , for a variety of observational reasons .
We present the results of a survey searching for companions to A- and B-type stars using the direct spectral detection method , which is sensitive to late-type companions within \sim 1 ^ { \prime \prime } of the primary and which has no inner working angle .
We estimate the temperatures and surface gravity of most of the 341 sample stars , and derive their masses and ages .
We additionally estimate the temperatures and masses of the 64 companions we find , 23 of which are new detections .
We find that the mass-ratio distribution for our sample has a maximum near q \sim 0.3 .
Our mass-ratio distribution has a very different form than in previous work , where it is usually well-described by a power law , and indicates that close companions to intermediate-mass stars experience significantly different accretion histories or formation mechanisms than wide companions .