(a) Archival HST image of SDSS J015804.75-005221.8 showing the position of the galaxy centroid (green “x”) and a ﹩1\sigma ﹩ error circle (red) centered on the position of PS16dtm as determined by relative astrometry using our ground-based images. North is up and east is to the left. The offset is ﹩0\mathop{.}\limits^{\prime\prime }03\pm 0\mathop{.}\limits^{\prime\prime }05﹩, indicating that PS16dtm is consistent with being located at the nucleus of SDSS J015804.75-005221.8. (b) HST/STIS-CCD image of PS16dtm. The detected source is a point source with no evidence for offset extended emission from the host galaxy.