Object name: ARP055
Arp 55/UGC 04881 is a pair of interacting galaxies in Lynx about 500 to 540 million light-years distant. Arp put it in his category for spirals with small, high surface brightness companions on their arms. The companion apparently is the galaxy seen against the very west end of the long arm. That galaxy is SDSS J091553.63+441937.4 but NED has no redshift data on it. So no way to know if this is just a line of sight galaxy or truly related. Or wasn't until Hubble imaged it. The HST image clearly indicates the companion is far beyond the colliding spirals as the level of resolution is very different. Arp apparently didn't care that there was no such data. It was appearance he was concerned with. Later astronomers could figure it out. It also appears he didn't realize the "spiral galaxy" is really two interacting galaxies. Or maybe he did but just didn't care. In any case, he never mentions this.