The Argos system was an uninhabited star system.

The Argos system was one of the possible next targets of the Crystalline Entity after it devastated Melona IV in 2368. The creature chose the Brechtian Cluster as its next target however. (TNG: "Silicon Avatar")

This system was only mentioned in dialogue.
The Star Trek Encyclopedia (4th ed., vol. 1, p. 44) located the Argos system in Federation space.