η Piscis Austrini

Location of η Piscis Austrini (circled)
Observation data Epoch J2000.0       Equinox J2000.0 ( ICRS)
Constellation	Piscis Austrinus
A
Right ascension	22h 00m 50.22454s [1]
Declination	−28° 27′ 13.4587″ [1]
Apparent magnitude (V)	5.742 [2]
B
Right ascension	22h 00m 50.34936s [3]
Declination	−28° 27′ 14.1460″ [3]
Apparent magnitude (V)	6.825 [2]
Characteristics
Spectral type	B6 III shell + B8.5 V [4]
U−B color index	−0.30 [5]
B−V color index	−0.10 [5]
Variable type	suspected [6]
Astrometry
Absolute magnitude (MV)	−1.53 [7]
A
Proper motion (μ)	RA: +15.289 [1]  mas/ yr Dec.: −0.096 [1]  mas/ yr
Parallax (π)	3.8087 ± 0.0932  mas [1]
Distance	860 ± 20  ly (263 ± 6  pc)
B
Proper motion (μ)	RA: +17.554 [3]  mas/ yr Dec.: −1.229 [3]  mas/ yr
Parallax (π)	4.5342 ± 0.3306  mas [3]
Distance	720 ± 50  ly (220 ± 20  pc)
Details
η PsA A
Mass	4.01±0.18 [8]  M☉
Luminosity	881 [9]  L☉
Surface gravity (log g)	3.48 [9]  cgs
Temperature	12,310 [9]  K
Rotational velocity (v sin i)	320 [9] km/s
Age	115 [10]  Myr
η PsA B
Mass	3.6 [11]  M☉
Surface gravity (log g)	4.17 [11]  cgs
Temperature	14,144 [11]  K
Metallicity [Fe/H]	−0.21 [11]  dex
Other designations
η PsA, 12 Piscis Austrini, CPD−29° 6659, HD 209014, HIP 108661, HR 8386, SAO 190822, WDS J22008-2827AB [12]
Database references
SIMBAD	data

Eta Piscis Austrini (η Piscis Austrini) is binary star ^[2] system in the southern constellation of Piscis Austrinus. As of 2000, the two components had an angular separation of 1.818  arc seconds along a position angle of 113.4°. The pair have a combined apparent visual magnitude of +5.43, ^[5] which is bright enough to be seen with the naked eye. Based upon an annual parallax shift of 3.99  mas as seen from the Earth, ^[13] the system is located roughly 820  light years from the Sun.

Although not catalogued formally as a variable star, brightness changes between magnitude 5,33 and 5.44 have been widely reported. ^{[6] [14]} The type of variability is thought to be related to its rapid rotation and a surrounding shell, and is tentatively given as a combination of a Be star and Maia variable. ^[15]

The magnitude 5.7 primary, component A, ^[2] is a blue-white hued Be star ^[10] with a stellar classification B6 III. ^[4] At 115 million years old, ^[10] the star is spinning rapidly with a projected rotational velocity of 265. ^[8] It has an estimated four times the mass of the Sun and is radiating 604 times the solar luminosity at an effective temperature of 11,272 K. ^[8] The secondary, component B, has a visual magnitude of 6.8 ^[2] and a spectral class of B8.5 V. ^[4]

Eta Piscis Austrini is moving through the Galaxy at a speed of 11.3 km/s relative to the Sun. Its projected Galactic orbit carries it between 23,600 and 30,800 light years from the center of the Galaxy. ^{[16][ unreliable source?]}

References