Gamma Piscis Austrini

Gamma Piscis Austrini, Latinized from γ Piscis Austrini, is three-star system^[7] in the southern constellation of Piscis Austrinus. It is visible to the naked eye with a combined apparent visual magnitude of +4.448.^[2] Based upon an annual parallax shift of 15.1 mas as seen from the Earth,^[1] the system is located about 216 light years from the Sun.

Gamma Piscis Austrini

Location of γ Piscis Austrini (circled)
Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Piscis Austrinus
Right ascension	22h 52m 31.5351s[1]
Declination	−32° 52′ 31.806″[1]
Apparent magnitude (V)	+4.448[2] (4.59 + 8.20)[3]
Characteristics
γ PsA A
Spectral type	A0 Vp(SrCrEu)[4]
U−B color index	−0.038[2]
B−V color index	−0.046[2]
γ PsA B
Spectral type	F5 V[5]
U−B color index	−0.08[5]
B−V color index	+0.44[5]
Astrometry
Radial velocity (Rv)	16.5±2.7[6] km/s
Proper motion (μ)	RA: −32.73 mas/yr[1] Dec.: −21.21 mas/yr[1]
Parallax (π)	15.14±0.57 mas[1]
Distance	215 ± 8 ly (66 ± 2 pc)
Absolute magnitude (MV)	−0.20/3.50[5]
Orbit[7]
Primary	Aa
Companion	Ab
Period (P)	15 yr
Semi-major axis (a)	143.5 mas (9.2 AU)
Details[7]
Aa
Mass	2.65 M☉
Radius	2.9 R☉
Surface gravity (log g)	3.92[8] cgs
Temperature	9,950 K
Rotation	2.542±0.001 d
Rotational velocity (v sin i)	47[8] km/s
Age	350 Myr
Ab
Mass	0.94 M☉
Radius	0.84 R☉
Temperature	5,500 K
B
Mass	1.20 M☉
Radius	1.15 R☉
Temperature	6,400 K
Other designations
γ PsA, 22 Piscis Austrini, CD−33°16270, HD 216336, HIP 112948, HR 8695, SAO 214153, WDS J22525-3253AB[9]
Database references
SIMBAD	γ PsA
	γ PsA A
	γ PsA B

The A and B components, as of 2010, are separated by 4 arc seconds in the sky along a position angle of 255°.^[10] The "A" component is itself a binary, made up of two stars orbiting each other with an orbital period of 15 years and a separation of nine astronomical units,^[7] with a combined apparent magnitude of 4.59.^[3] The component Aa has 2.65 times more mass than the Sun and 2.9 times its radius, being a chemically peculiar star^[7] with a spectral type A0 Vp(SrCrEu).^[4] The Ab component is smaller, at 0.94 times the Sun's mass and 0.84 times its radius.^[7] The fainter magnitude 8.20^[3] companion, component B, is an F-type main sequence star with a class of F5 V.^[5] It has 20% more mass than the Sun and a radius 15% larger.^[7]

Gamma Piscis Austrini is moving through the Galaxy at a speed of 24.1 km/s relative to the Sun. Its projected Galactic orbit carries it between 21,605 and 30,903 light-years from the center of the Galaxy. It came closest to the Sun 1.8 million years ago at a distance of 157 light-years.^[11]

The current age of the system is 350 million years. It will become a triple white dwarf system within 14 billion years.^[7]

Naming

In Chinese, 敗臼 (Bài Jiù), meaning Decayed Mortar, refers to an asterism consisting of refers to an asterism consisting of γ Piscis Austrini, γ Gruis, λ Gruis and 19 Piscis Austrini. Consequently, the Chinese name for γ Piscis Austrini itself is 敗臼三 (Bài Jiù sān, English: the Third Star of Decayed Mortar.)^[12]