Four HST combined and calibrated images (.drz file for the F435W filter and .drc files for the other three filters) centred on the position of the X-ray source X17. In the top-left panel, the F435W image from the December 2004 ACS/HRC observation is shown. The image in the top-right panel was taken in the F390W filter as part of the WFC3/UVIS observations of April 2012. The bottom panels, from left to right, display the F225W and F275W WFC3/UVIS images from September 2016. In each panel, the X-ray source position is indicated by a cyan cross, along with a cyan circle whose radius represents the uncertainty in the X-ray position, unc_X. The red circle marks the location of the counterpart X17^c.