Theta Piscis Austrini
Location of θ Piscis Austrini (circled)
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Piscis Austrinus
Right ascension 21h 47m 44.14993s[1]
Declination −30° 53′ 53.9027″[1]
Apparent magnitude (V) +5.01[2]
Characteristics
Spectral type A1 V + A1 V[3]
B−V color index +0.04[2]
Astrometry
Radial velocity (Rv)+12.80±1.8[4] km/s
Proper motion (μ) RA: −34.40[1] mas/yr
Dec.: −0.08[1] mas/yr
Parallax (π)10.16 ± 0.40 mas[1]
Distance320 ± 10 ly
(98 ± 4 pc)
Absolute magnitude (MV)+0.06[5]
Orbit[3]
Period (P)19.957±0.050 yr
Semi-major axis (a)0.137±0.004″
Eccentricity (e)0.256±0.030
Inclination (i)103±2°
Longitude of the node (Ω)29.1±2.0°
Periastron epoch (T)2006.00 ± 0.07
Argument of periastron (ω)
(secondary)		199±6°
Details
θ PsA A
Mass2.32±0.33[3] M☉
Luminosity86[5] L☉
Surface gravity (log g)4.05[6] cgs
Temperature9,716±330[6] K
Rotational velocity (v sin i)150[6] km/s
Age281[6] Myr
θ PsA B
Mass2.32±0.33[3] M☉
Other designations
θ PsA, 10 Piscis Austrini, CPD−31° 6596, HD 207155, HIP 107608, HR 8326, SAO 213292, WDS J21477-3054AB[7]
Database references
SIMBADdata

Theta Piscis Austrini, Latinized as θ Piscis Austrini, is a binary star[8] system in the southern constellation of Piscis Austrinus. It is faintly visible to the naked eye with a combined apparent visual magnitude of +5.01.[2] Based upon an annual parallax shift of 10.16 mas as seen from the Earth,[1] the system is located around 320 light years from the Sun. The system is drifting further away with a radial velocity of +13 km/s.[4]

The binary nature of this system was discovered in 1951 by South African astronomer W. S. Finsen. Both components A and B have the same apparent magnitude. They orbit each other with a period of 20 years and an eccentricity of 0.256. The pair are A-type main sequence stars with stellar classifications of A1 V.[3] A magnitude 11.3 visual companion star, labelled component C, is located at an angular separation of 33.2 arc seconds along a position angle of 342°, as of 1999.[9]

Theta Piscis Austrini is moving through the Galaxy at a speed of 21.3 km/s relative to the Sun. Its projected Galactic orbit carries it between 22,629 and 38,431 light-years from the center of the Galaxy. Theta Piscis Austrini came closest to the Sun 2.7 million years ago at a distance of 256 light-years.[5]

Naming

In Chinese, 天錢 (Tiān Qián), meaning Celestial Money, refers to an asterism consisting of refers to an asterism consisting of θ Piscis Austrini, 13 Piscis Austrini, ι Piscis Austrini, μ Piscis Austrini and τ Piscis Austrini. Consequently, the Chinese name for θ Piscis Austrini itself is 天錢二 (Tiān Qián èr, English: the Second Star of Celestial Money.)[10]

References

  1. 1 2 3 4 5 6 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. 1 2 3 Nicolet, B. (1978), "Photoelectric photometric Catalogue of homogeneous measurements in the UBV System", Astronomy and Astrophysics Supplement Series, 34: 1–49, Bibcode:1978A&AS...34....1N.
  3. 1 2 3 4 5 Docobo, J. A.; Andrade, M. (2013), "Dynamical and physical properties of 22 binaries discovered by W. S. Finsen", Monthly Notices of the Royal Astronomical Society, 428 (1): 321–339, Bibcode:2013MNRAS.428..321D, doi:10.1093/mnras/sts045.
  4. 1 2 Kharchenko, N. V.; et al. (2007), "Astrophysical supplements to the ASCC-2.5: Ia. Radial velocities of ˜55000 stars and mean radial velocities of 516 Galactic open clusters and associations", Astronomische Nachrichten, 328 (9): 889, arXiv:0705.0878, Bibcode:2007AN....328..889K, doi:10.1002/asna.200710776, S2CID 119323941.
  5. 1 2 3 Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters, 38 (5): 331, arXiv:1108.4971, Bibcode:2012AstL...38..331A, doi:10.1134/S1063773712050015, S2CID 119257644.
  6. 1 2 3 4 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.
  7. ↑ "tet PsA -- Double or multiple star", SIMBAD Astronomical Database, Centre de Données astronomiques de Strasbourg, retrieved 2017-05-18.
  8. ↑ 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.
  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, retrieved 2015-07-22
  10. ↑ (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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