Pi Piscis Austrini
Star in the constellation Piscis Austrinus
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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] It is drifting closer with a radial velocity of −6 km/s.[7] 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]
 | |
| Observation data Epoch J2000 Equinox ICRS | |
|---|---|
| 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) | −5.97±0.11[7] 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[8] 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[8] cgs |
| Temperature | 7,003+195 −216[1] K |
| Metallicity [Fe/H] | +0.12[2] dex |
| Age | 474[8] Myr |
| Other designations | |
| π PsA, CD−35°15630, GC 32122, GJ 886.2, GJ 9807, HD 217792, HIP 113860, HR 8767, SAO 214275[9] | |
| 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]
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.[11] 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.[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.[13] Koen and Eyer examined the Hipparcos data for the star, and report it to be a microvariable with a period of 1.06039 days.[14] On the other hand, the General Catalog of Variable Stars reports the star's brightness as constant,[15] and in separate studies Michel Petit[16] and E. Janot-Pacheco could not detect any change in brightness.[11]
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.[17] The cooler secondary companion has a class of F3 V.[5] The system appears to be a source of X-ray emission.[18]