V539 Arae (Bayer designation Nu Arae (ν Arae / ν Ara)) is a triple star system in the southern constellation of Ara. It is a variable star, the brightness of which varies from magnitude 5.71 to 6.24, making it faintly visible to the naked eye under good observing conditions. Based upon an annual parallax shift of, this system is at a distance of roughly 1000abbr=offNaNabbr=off from Earth.
In 1930, Ferdinand Johannes Neubauer found that the star (usually called Boss 4496 at the time) is a spectroscopic binary. He did not detect any brightness variability. Eclipses were first reported by E. Schoeffel and U. Kohler in 1965. The period they reported is 1/2 the currently accepted value, because they did not realize that the light curve has a deep secondary minimum.
The core members of this system, ν Ara AB, consist of a pair of B-type main-sequence stars in a close orbit with a period of 3.169 days and an eccentricity of 0.06. Their respective stellar classifications are B2 V and B3 V, and they have a combined visual magnitude of 5.65. Because the orbital plane lies close to the line of sight from the Earth, this pair form a detached eclipsing binary of the Algol type. The eclipse of the primary causes a decrease of 0.52 in magnitude, while the secondary eclipse decreases the magnitude by 0.43. At an angular separation of 12.34 arcseconds, is the tertiary component of this system; a magnitude 9.40 A-type main-sequence star with a classification of A1 V.
The system is sometimes referred as Upsilon Arae (υ Arae), and more generally unlettered.[1]