They are stars imported from real catalogues. (The wiki article linked is about something else.) When they were automatically converted, many near each other ended up in such lines: there is error from uncertainty in the real stars' positions, but that doesn't translate well into the game. Besides, all our actual measurements are from one star system.
Such so-called catalogue stars are always cool to visit, because unlike the procedurally generated ones, they do exist in reality. There's also that some kinds of stars only exist when imported, and aren't generated by the Forge.
However, don't expect to find many untagged. If they are easy to spot and near popular areas (like the Eagle nebula), chances are they have been surveyed and tagged thoroughly. Well, out of the way though, you might still find some new catalogue systems, most likely from HIP or HD.
In comparison, if the system's name contains the word "sector", it's a procedurally generated one, with the name of a nearby real cluster / nebula / etc stamped on top of it.