ALMA images of the averaged data of 4U 1728−34 (left) and 4U 1820−30 (right) at 301.99 GHz. The images are cutouts of the full field-of-view (FoV, half power beam width of 17′′) centred on the detected sources. Left panel: 4U 1728−34 is the brightest source in the ALMA FoV with a flux density of 1.40 mJy beam^-1. A second, weaker source is detected to the southwest of 4U 1728−34 with a flux density of 0.10 mJy beam^-1. Right panel: 4U 1820−30 is the source at the bottom-right of the image, with a flux density of 0.40 mJy beam^-1. Two additional sources are visible to the northeast, one of which is marginally extended (see Table 2). Contours are overlaid in the zoomed images at levels of ± (2)ⁿσ significance with respect to a noise of σ = 20μJy beam^-1, where n = 2, 3, 4, 5...15. The synthesised beam is shown at the lower-left corner of each image.