There remain significant uncertainties in the origin and evolution of black holes in binary systems , in particular regarding their birth sites and the influence of natal kicks .
These are long-standing issues , but their debate has been reinvigorated in the era of gravitational wave detections and the improving precision of astrometric measurements .
Using recent and archival characterisation of Galactic black hole X-ray binaries ( BHXBs ) , we report here an apparent anticorrelation between P _ { orb } ( system orbital periods ) and scatter in z ( elevation above the Galactic plane ) .
The absence of long period sources at high z is not an obvious observational bias , and two possible explanatory scenarios are qualitatively explored : ( 1 ) a disc origin for BHXBs followed by natal kicks producing the scatter in z , with only the tightest binaries preferentially surviving strong kicks ; ( 2 ) a halo origin , with P _ { orb } shortening through dynamical interactions in globular clusters ( GCs ) .
For the latter case , we show a correspondence in z -scatter between BHXBs and the GCs with most compact core radii of < 0.1 pc .
However , the known absence of outbursting BHXB transients within Galactic GCs remains puzzling in this case , in contrast to the multitude of known GC neutron star XRBs .
These results provide an interesting observational constraint for any black hole binary evolutionary model to satisfy .