Pi Piscis Austrini

Pi Piscis Austrini, Latinized from π Piscis Austrini, is binary star system in the southern constellation of Piscis Austrinus, near the eastern constellation border with Sculptor. It has a yellow-white hue and is visible to the naked eye as a dim point of light with an apparent visual magnitude of 5.12. The system is located at a distance of 92 light-years from the Sun based on parallax. Its radial velocity is poorly constrained, but it appears to be drifting closer at a rate of around −6 km/s. Pi Piscis Austrini is moving through the galaxy at a velocity of 16.3 km/s relative to the Sun. Its projected galactic orbit carries it between 24,000 and 37,500 light-years from the center of the galaxy.

This is a single-lined spectroscopic binary system with an orbital period of 178.3 days and an eccentricity of 0.53. The primary component is an F-type main-sequence star with a stellar classification of F1 V Fe-0.8.

As of 2023, there appears to be no consensus in the astronomical literature about whether or not Pi Piscis Austrini is a variable star, and if it is variable, what type of variable star it is. In 1965 it was designated a classical Cepheid variable star with a visual (V) band brightness that varied by 0.3 magnitudes over a period of 7.975 days. The AAVSO's International Variable Star index lists it as a Gamma Doradus variable, with a V band magnitude range of 5.10 to 5.12. Axel Thomas, writing in the AAVSO's Journal, reports that the star appears to be a semiregular variable star, varying by 0.7 magnitudes in V band over a period of 8.625 days. Koen and Eyer examined the Hipparcos data for the star, and report it to be a microvariable with a period of 1.06039 days. On the other hand, the General Catalog of Variable Stars reports the star's brightness as constant, and in separate studies Michel Petit and E. Janot-Pacheco could not detect any change in brightness.

Pi Piscis Austrini displays an infrared excess, suggesting a circumstellar disk is orbiting at a radius of $−6.0$ with a mean temperature of 90 K. The cooler secondary companion has a class of F3 V. The system appears to be a source of X-ray emission.