GaiaHub: A method for combining data from the Gaia and Hubble space telescopes to derive improved proper motions for faint stars

Understand

We present GaiaHub, a publicly available tool that combines $Gaia$ measurements with $Hubble$ $Space$ $Telescope$ ($HST$) archival images to derive proper motions (PMs).

• It increases the scientific impact of both observatories beyond their individual capabilities.
• $Gaia$ provides PMs across the whole sky, but the limited mirror size and time baseline restrict the best PM performance to relatively bright stars.
• $HST$ can measure accurate PMs for much fainter stars over a small field, but this requires two epochs of observation which are not always available.