Gamma Piscis Austrini

Gamma Piscis Austrini (γ Piscis Austrini) is binary star[3] system in the southern constellation of Piscis Austrinus. It is visible to the naked eye with a combined apparent visual magnitude of +4.448.[2] As of 2010, the pair had an angular separation of 4 arc seconds along a position angle of 255°.[9] Based upon an annual parallax shift of 15.14 mas as seen from the Earth,[1] the system is located about 215 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 31.53513s[1]
Declination −32° 52′ 31.8059″[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[1] mas/yr
Dec.: −21.21[1] mas/yr
Parallax (π)15.14 ± 0.57[1] mas
Distance215 ± 8 ly
(66 ± 2 pc)
Absolute magnitude (MV)−0.20/3.50[5]
Details[7]
γ PsA A
Mass2.63 M☉
Surface gravity (log g)3.92 cgs
Temperature10,776±366 K
Rotational velocity (v sin i)47 km/s
Age214 Myr
Other designations
γ PsA, 22 Piscis Austrini, CD−33° 16270, HD 216336, HIP 112948, HR 8695, SAO 214153, WDS J22525-3253AB[8]
Database references
SIMBADγ PsA
γ PsA A
γ PsA B

The magnitude 4.59[3] primary, component A, is a white-hued, chemically peculiar A-type main sequence star with a stellar classification of A0 Vp(SrCrEu).[4] It is an estimated 214 million years old with 2.63 times the mass of the Sun. The fainter magnitude 8.20[3] companion, component B, is an F-type main sequence star with a class of F5 V.[5]

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 21,600 and 30,800 light years from the center of the Galaxy. It came closest to the Sun 1.8 million years ago when it had brightened to magnitude 3.78 from a distance of 157 light years.[10]

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.)[11]

References
  1. van Leeuwen, F. (2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357, S2CID 18759600.
  2. Rakos, K. D.; et al. (February 1982), "Photometric and astrometric observations of close visual binaries", Astronomy and Astrophysics Supplement Series, 47: 221–235, Bibcode:1982A&AS...47..221R.
  3. Eggleton, P. P.; Tokovinin, A. A. (September 2008), "A catalogue of multiplicity among bright stellar systems", Monthly Notices of the Royal Astronomical Society, 389 (2): 869–879, arXiv:0806.2878, Bibcode:2008MNRAS.389..869E, doi:10.1111/j.1365-2966.2008.13596.x, S2CID 14878976.
  4. Abt, Helmut A.; Morrell, Nidia I. (July 1995), "The Relation between Rotational Velocities and Spectral Peculiarities among A-Type Stars", Astrophysical Journal Supplement, 99: 135, Bibcode:1995ApJS...99..135A, doi:10.1086/192182.
  5. Corbally, C. J. (1984), "Close visual binaries. I - MK classifications", Astrophysical Journal Supplement Series, 55: 657, Bibcode:1984ApJS...55..657C, doi:10.1086/190973.
  6. Gontcharov, G. A. (2006), "Pulkovo Compilation of Radial Velocities for 35 495 Hipparcos stars in a common system", Astronomy Letters, 32 (11): 759–771, arXiv:1606.08053, Bibcode:2006AstL...32..759G, doi:10.1134/S1063773706110065, S2CID 119231169.
  7. David, Trevor J.; Hillenbrand, Lynne A. (2015), "The Ages of Early-Type Stars: Strömgren Photometric Methods Calibrated, Validated, Tested, and Applied to Hosts and Prospective Hosts of Directly Imaged Exoplanets", The Astrophysical Journal, 804 (2): 146, arXiv:1501.03154, Bibcode:2015ApJ...804..146D, doi:10.1088/0004-637X/804/2/146, S2CID 33401607.
  8. "gam PsA -- Double or multiple star", SIMBAD Astronomical Database, Centre de Données astronomiques de Strasbourg, retrieved 2017-05-18.
  9. Mason, B. D.; et al. (2014), "The Washington Visual Double Star Catalog", The Astronomical Journal, 122 (6): 3466, Bibcode:2001AJ....122.3466M, doi:10.1086/323920.
  10. Gamma Piscis Austrini (HIP 112948) Archived 2015-09-23 at the Wayback Machine
  11. (in Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 5 日
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