  Precise and accurate measurements of distances to Galactic X-ray binaries
(XRBs) reduce uncertainties in the determination of XRB physical parameters. We
have cross-matched the XRB catalogues of Liu et al. (2006, 2007) to the results
of Gaia Data Release 2. We identify 86 X-ray binaries with a Gaia candidate
counterpart, of which 32 are low-mass X-ray binaries (LMXBs) and 54 are
high-mass X-ray binaries (HMXBs). Distances to Gaia candidate counterparts are,
on average, consistent with those measured by Hipparcos and radio parallaxes.
When compared to distances measured by Gaia candidate counterparts, distances
measured using Type I X-ray bursts are systematically larger, suggesting that
these bursts reach only 50% of the Eddington limit. However, these results are
strongly dependent on the prior assumptions used for estimating distance from
the Gaia parallax measurements. Comparing positions of Gaia candidate
counterparts for XRBs in our sample to positions of spiral arms in the Milky
Way, we find that HMXBs exhibit mild preference for being closer to spiral
arms; LMXBs exhibit mild preference for being closer to inter-arm regions.
LMXBs do not exhibit any preference for leading or trailing their closest
spiral arm. HMXBs exhibit a mild preference for trailing their closest spiral
arm. The lack of a strong correlation between HMXBs and spiral arms may be
explained by star formation occurring closer to the midpoint of the arms, or a
time delay between star formation and HMXB formation manifesting as a spatial
separation between HMXBs and the spiral arm where they formed.
