Epsilon Piscis Austrini

Epsilon Piscis Austrini, Latinized from ε Piscis Austrini, is a blue-white hued star in the southern constellation of Piscis Austrinus. It is visible to the naked eye with an apparent visual magnitude of +4.17.[2] Based upon an annual parallax shift of 8.0981 ± 0.3582 mas as seen from the GAIA satellite, the system is located roughly 400 light years from the Sun.[6]

Epsilon Piscis Austrini
Location of ε Piscis Austrini (circled)
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Piscis Austrinus
Right ascension 22h 40m 39.34075s[1]
Declination −27° 02′ 37.0157″[1]
Apparent magnitude (V) +4.17[2]
Characteristics
Spectral type B8 Ve[3] or B8 IVe[4]
U−B color index −0.31[2]
B−V color index −0.11[2]
Astrometry
Radial velocity (Rv)+1.1±2.8[5] km/s
Proper motion (μ) RA: +23.22[1] mas/yr
Dec.: −0.16[1] mas/yr
Parallax (π)8.0981 ± 0.3582 mas[6]
Distance400 ± 20 ly
(123 ± 5 pc)
Absolute magnitude (MV)−1.66[4]
Details
Mass4.10±0.19[7] M☉
Radius3.2[8] R☉
Luminosity661[7] L☉
Surface gravity (log g)3.93[9] cgs
Temperature11,066[7] K
Rotational velocity (v sin i)216[7] km/s
Other designations
ε PsA, 18 Piscis Austrini, CPD−27° 7442, FK5 854, HD 214748, HIP 111954, HR 8628, SAO 191318[10]
Database references
SIMBADdata

This is a B-type main sequence star with a stellar classification of B8 Ve.[3] It is a Be star that is spinning rapidly with a projected rotational velocity of 216 km/s,[7] compared to an equatorial critical velocity of 301 km/s.[9] The star has 4.1 times the mass of the Sun and is radiating 661 times the solar luminosity from its photosphere at an effective temperature of 11,066 K.[7]

Epsilon Piscis Austrini is moving through the Galaxy at a speed of 18.7 km/s relative to the Sun. Its projected Galactic orbit carries it between 23,917 and 28,138 light-years from the center of the Galaxy.[11]

Naming

In Chinese, 羽林軍 (Yǔ Lín Jūn), meaning Palace Guard, refers to an asterism consisting of:

Consequently, the Chinese name for ε Piscis Austrini itself is 羽林軍八 (Yǔ Lín Jūn bā, English: the Eighth Sixth Star of Palace Guard.)[12]

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. Feinstein, A.; Marraco, H. G. (November 1979), "The photometric behavior of Be Stars", Astronomical Journal, 84: 1713–1725, Bibcode:1979AJ.....84.1713F, doi:10.1086/112600.
  3. Abt, Helmut A.; Levato, Hugo; Grosso, Monica (July 2002), "Rotational Velocities of B Stars", The Astrophysical Journal, 573 (1): 359–365, Bibcode:2002ApJ...573..359A, doi:10.1086/340590.
  4. 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.
  5. Gontcharov, G. A. (November 2006), "Pulkovo Compilation of Radial Velocities for 35495 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.
  6. Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
  7. Zorec, J.; Royer, F. (2012), "Rotational velocities of A-type stars. IV. Evolution of rotational velocities", Astronomy & Astrophysics, 537: A120, arXiv:1201.2052, Bibcode:2012A&A...537A.120Z, doi:10.1051/0004-6361/201117691, S2CID 55586789.
  8. Pasinetti Fracassini, L. E.; et al. (February 2001), "Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS)", Astronomy and Astrophysics (3rd ed.), 367: 521–524, arXiv:astro-ph/0012289, Bibcode:2001A&A...367..521P, doi:10.1051/0004-6361:20000451, S2CID 425754.
  9. Chauville, J.; et al. (November 2001), "High and intermediate-resolution spectroscopy of Be stars 4481 lines", Astronomy and Astrophysics, 378: 8618–82, Bibcode:2001A&A...378..861C, doi:10.1051/0004-6361:20011202.
  10. "eps PsA -- Be Star", SIMBAD Astronomical Database, Centre de Données astronomiques de Strasbourg, retrieved 2017-05-18.
  11. 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.
  12. (in Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 7 日
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