Epsilon Apodis

Epsilon Apodis, Latinized from ε Apodis, is the Bayer designation for a star in the southern circumpolar constellation of Apus. It has an apparent visual magnitude of 5.06,[2] which is bright enough to be viewed from dark suburban skies. Based upon parallax measurements, it is at a distance of roughly 640 light-years (200 parsecs) from Earth.[1]

Epsilon Apodis
Location of ε Apodis (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Apus
Right ascension 14h 22m 23.16467s[1]
Declination –80° 06′ 32.2053″[1]
Apparent magnitude (V) 5.06[2]
Characteristics
Spectral type B3 V[3]
U−B color index –0.610[2]
B−V color index –0.121[2]
Variable type γ Cas[4]
Astrometry
Radial velocity (Rv)+4.5[5] km/s
Proper motion (μ) RA: –8.683[6] mas/yr
Dec.: –13.542[6] mas/yr
Parallax (π)6.9644 ± 0.2978[6] mas
Distance470 ± 20 ly
(144 ± 6 pc)
Absolute magnitude (MV)−1.41[7]
Details
Mass6.15 ± 0.71[8] M☉
Radius3.9[9] R☉
Luminosity1,614[8] L☉
Surface gravity (log g)4.18[10] cgs
Temperature17,050[8] K
Metallicity [Fe/H]–0.02[10] dex
Rotational velocity (v sin i)255[11] km/s
Age38.3 ± 4.4[12] Myr
Other designations
ε Aps, CD–79 559, HD 124771, HIP 70248, HR 5336, SAO 257142.[13]
Database references
SIMBADdata

Based upon a stellar classification of B3 V,[3] this is a massive, B-type main sequence star that is generating energy through the fusion of hydrogen at its core. Epsilon Apodis has more than six[8] times the mass of the Sun and nearly four[9] times the Sun's radius. It is radiating 1,614[8] times as much luminosity as the Sun from its outer envelope at an effective temperature of 17,050 K.[8] At this heat, it has a blue-white glow that is a characteristic of B-type stars.[14]

It is spinning rapidly, with a projected rotational velocity of 255 km/s[11] giving a lower bound for the azimuthal velocity along the equator. Epsilon Apodis is classified as a Gamma Cassiopeiae type[4] variable star and its brightness varies between magnitudes 4.99 and 5.04.[15]

Naming

In Chinese caused by adaptation of the European southern hemisphere constellations into the Chinese system, 異雀 (Yì Què), meaning Exotic Bird, refers to an asterism consisting of ε Apodis, ζ Apodis, ι Apodis, β Apodis, γ Apodis, δ Octantis, δ1 Apodis, η Apodis and α Apodis. Consequently, ε Apodis itself is known as 異雀九 (Yì Què jiǔ, English: the Ninth Star of Exotic Bird.)[16]

References
  1. van Leeuwen, F. (November 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.
  2. Gutierrez-Moreno, Adelina; Moreno, Hugo (June 1968), "A photometric investigation of the Scorpio-Centaurus association", Astrophysical Journal Supplement, 15: 459, Bibcode:1968ApJS...15..459G, doi:10.1086/190168.
  3. Houk, Nancy (1979), Michigan catalogue of two-dimensional spectral types for the HD stars, 1, Ann Arbor, Michigan: Dept. of Astronomy, University of Michigan, Bibcode:1978mcts.book.....H.
  4. Kazarovets, E. V.; et al. (January 1999), "The 74th Special Name-list of Variable Stars", Information Bulletin on Variable Stars, 4659: 1, Bibcode:1999IBVS.4659....1K.
  5. Evans, D. S. (June 20–24, 1966), "The Revision of the General Catalogue of Radial Velocities", in Batten, Alan Henry; Heard, John Frederick (eds.), Determination of Radial Velocities and their Applications, Proceedings from IAU Symposium no. 30, University of Toronto: International Astronomical Union, Bibcode:1967IAUS...30...57E.
  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.
  7. 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.
  8. Hohle, M. M.; Neuhäuser, R.; Schutz, B. F. (April 2010), "Masses and luminosities of O- and B-type stars and red supergiants", Astronomische Nachrichten, 331 (4): 349, arXiv:1003.2335, Bibcode:2010AN....331..349H, doi:10.1002/asna.200911355.
  9. Pasinetti Fracassini, L. E.; Pastori, L.; Covino, S.; Pozzi, A. (February 2001). "Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS) - Third edition - Comments and statistics". Astronomy and Astrophysics. 367 (2): 521–524. arXiv:astro-ph/0012289. Bibcode:2001A&A...367..521P. doi:10.1051/0004-6361:20000451.
  10. Saffe, C.; et al. (October 2008), "Spectroscopic metallicities of Vega-like stars", Astronomy and Astrophysics, 490 (1): 297–305, arXiv:0805.3936, Bibcode:2008A&A...490..297S, doi:10.1051/0004-6361:200810260.
  11. Uesugi, Akira; Fukuda, Ichiro (1970), "Catalogue of rotational velocities of the stars", Contributions from the Institute of Astrophysics and Kwasan Observatory, University of Kyoto, Bibcode:1970crvs.book.....U.
  12. Tetzlaff, N.; Neuhäuser, R.; Hohle, M. M. (January 2011), "A catalogue of young runaway Hipparcos stars within 3 kpc from the Sun", Monthly Notices of the Royal Astronomical Society, 410 (1): 190–200, arXiv:1007.4883, Bibcode:2011MNRAS.410..190T, doi:10.1111/j.1365-2966.2010.17434.x.
  13. "eps Aps -- Be Star", SIMBAD, Centre de Données astronomiques de Strasbourg, retrieved 2012-07-08.
  14. "The Colour of Stars", Australia Telescope, Outreach and Education, Commonwealth Scientific and Industrial Research Organisation, December 21, 2004, archived from the original on 2012-03-18, retrieved 2012-01-16.
  15. Samus, N. N.; Durlevich, O. V.; Kazarovets, R. V., "eps Aps", General Catalogue of Variable Stars, Sternberg Astronomical Institute, retrieved 2012-07-09.
  16. (in Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 29 日
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