Neutral zone map
The Nequencia Alpha system was a star system located near Romulan space.
In 2369, the USS Enterprise-D scanned the planets within this system in search of evidence of a Romulan prison camp. Finding no such evidence, the starship went onward to the Carraya sector, a system located even closer to Romulan space, to continue the investigation. (TNG: "Birthright, Part II")
According to the Star Trek: Star Charts, on page 63, Nequencia was a binary star system. The Alpha system's primary was a red dwarf, while the Beta system's primary was a yellow dwarf. This Romulan system was located in the Beta Quadrant.