Progenitor identification of iPTF13bvn based on registering an HST WFC3 image of the SN to a stacked archival pre-explosion HST ACS image. The left panels show an image taken when iPTF13bvn was clearly visible, and the panels to the right show the pre-explosion image. The field of view in the upper panels is 16″ × 16″. The location of the SN is marked by the grey dashed square in the upper panels, and the lower panels show this region in detail. Common point sources used for the registration are marked with boxed black circles. The intensity contours of the bright SN in the lower-left panel are traced with black dashed lines. The centroid of the SN is indicated with red circles in each panel; the smaller and larger red circles respectively represent 1σ and 5σ uncertainties in the registration. The lower-right panel shows the progenitor identification; the centroid of the SN is directly coincident with one object.