HONIR J-band images and subtracted images for the seven flat-spectrum radio sources catalogued in the preliminary BROS when we started the follow-up observations (table 2). From left to right, HONIR J-band image on 2017 September 23, HONIR J-band image on 2017 September 24, subtracted HONIR J-band image (September 23–24), and PS1 r-band image are shown for each BROS source. The red circles on the PS1 images are NVSS radio locations with radii of 2″, which are typical positional errors of NVSS sources. (Color online)