Pi Piscis Austrini

Pi Piscis Austrini, Latinized from π Piscis Austrini, is binary star^[5] 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.^[2] The system is located at a distance of 92 light-years from the Sun based on parallax.^[1] Its radial velocity is poorly constrained, but it appears to be drifting closer at a rate of around −6 km/s.^[2] 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.^[2]

Pi Piscis Austrini

Location of π Piscis Austrini (circled)
Observation data Epoch J2000      Equinox J2000
Constellation	Piscis Austrinus
Right ascension	23h 03m 29.81653s[1]
Declination	−34° 44′ 57.8827″[1]
Apparent magnitude (V)	5.12[2]
Characteristics
Spectral type	F1 V Fe-0.8[3] + F3 V[4][5]
U−B color index	+0.00[6]
B−V color index	+0.29[6]
Astrometry
Radial velocity (Rv)	−6.0±4.2[2] km/s
Proper motion (μ)	RA: +72.789[1] mas/yr Dec.: +83.569[1] mas/yr
Parallax (π)	35.3691±0.2124 mas[1]
Distance	92.2 ± 0.6 ly (28.3 ± 0.2 pc)
Absolute magnitude (MV)	+2.78[2]
Orbit[7]
Period (P)	178.3177±0.0038 d
Semi-major axis (a)	≥ 0.296 AU
Eccentricity (e)	0.5286±0.0041
Periastron epoch (T)	2,435,319.73±0.25
Argument of periastron (ω) (secondary)	2.62±0.81°
Semi-amplitude (K1) (primary)	21.28±0.16 km/s
Details
A
Mass	1.51[3] M☉
Radius	1.64+0.11 −0.08[1] R☉
Luminosity	5.85±0.04[1] L☉
Surface gravity (log g)	4.30±0.14[3] cgs
Temperature	7,003+195 −216[1] K
Metallicity [Fe/H]	+0.12[2] dex
Age	474[3] Myr
Other designations
π PsA, CD−35°15630, GC 32122, GJ 886.2, GJ 9807, HD 217792, HIP 113860, HR 8767, SAO 214275[8]
Database references
SIMBAD	data

This is a single-lined spectroscopic binary system with an orbital period of 178.3 days and an eccentricity of 0.53.^[7] The primary component is an F-type main-sequence star with a stellar classification of F1 V Fe-0.8.^[3]

A light curve for Pi Piscis Austrini, plotted from Hipparcos data^[9]

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.^[10] 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.^[11] 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.^[12] Koen and Eyer examined the Hipparcos data for the star, and report it to be a microvariable with a period of 1.06039 days.^[13] On the other hand, the General Catalog of Variable Stars reports the star's brightness as constant,^[14] and in separate studies Michel Petit^[15] and E. Janot-Pacheco could not detect any change in brightness.^[10]

Pi Piscis Austrini displays an infrared excess, suggesting a circumstellar disk is orbiting at a radius of 23 AU with a mean temperature of 90 K.^[16] The cooler secondary companion has a class of F3 V.^[5] The system appears to be a source of X-ray emission.^[17]