I thought that there was at least one other reference to Antares but I did not find it until after I had published the first "Antares" post. The short story, "Esau," mentions a star, called Osman by its discoverer, which is beyond Antares on the remote edge of Polesotechnic League activities in van Rijn's time. Thus, the word "Antares" signifies not just a particular star but an interstellar frontier.
Osman's one inhabited, subjovian planet, Suleiman, produces a plant called bluejack, used as a spice and tonic by hydrogen breathers. Solar Spice & Liquors sells bluejack to the Baburites whose star, Mogul, is about thirty light years from Osman. Thirty years later, Babur seizes Mirkheim and invades Hermes. After the Babur War, Hermes takes over Mirkheim and Babur becomes a Hermetian protectorate.
I think this means that Antares, Osman, Mogul, Maia (Hermes' sun) and sunless Mirkheim are in the same volume of space.
"Antares burned brightest. Mogul was sufficiently near to rival it, an orange spark..."
-Poul Anderson, Flandry's Legacy (New York, 2012), p. 26.