In 2399, the location of Arcturus was labeled on a Federation star chart that was in Fleet Admiral Kirsten Clancy's office at Starfleet Headquarters. This system was in or near to Federation space. (PIC: "Maps and Legends")
Arcturus is a real star described as the densely populated homeworld of the Arcturians. (The Making of Star Trek: The Motion Picture, p. 131; Star Trek: The Magazine Volume 2, Issue 9, "Who is that Alien?", January 2002)
In an early story outline for the Star Trek: The Original Series episode "The Cage" (29 June 1964), when the lead was still Robert April, the captive creatures kept by the Talosians in their zoo-menagerie included a race that was reminiscent of a "civilization April himself has seen –the intelligent Lemur-life of a Class M planet in the Arcturus system." (The Making of Star Trek, p. 59)
The term "Arcturus" would also appear in the pronunciation guide of the script for the Star Trek: The Next Generation episode "Attached" (7 September 1993), but further references to the term are excised from the remainder of the script.
According to Star Trek: Star Charts ("United Federation of Planets I") and Stellar Cartography: The Starfleet Reference Library ("Federation Historical Highlights, 2161-2385"), the primary of the Arcturus (Alpha Boötis) system was a K-class star. A planet in this system was known as Arcturus, which was a Federation member in the late 24th century.