Epsilon Apodis

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Epsilon Apodis
Diagram showing star positions and boundaries of the Apus constellation and its surroundings
Cercle rouge 100%.svg

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: –9.51[1] mas/yr
Dec.: –14.34[1] mas/yr
Parallax (π) 5.06 ± 0.22[1] mas
Distance 640 ± 30 ly
(198 ± 9 pc)
Details
Mass 6.15 ± 0.71[6] M
Radius 3.9[7] R
Luminosity 1,614[6] L
Surface gravity (log g) 4.18[8] cgs
Temperature 17,050[6] K
Metallicity [Fe/H] –0.02[8] dex
Rotational velocity (v sin i) 255[9] km/s
Age 38.3 ± 4.4[10] Myr
Other designations
CD–79 559, HD 124771, HIP 70248, HR 5336, SAO 257142.[11]

Epsilon Apodis (ε Aps, 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]

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[6] times the mass of the Sun and nearly four[7] times the Sun's radius. It is radiating 1,614[6] times as much luminosity as the Sun from its outer envelope at an effective temperature of 17,050 K.[6] At this heat, it has a blue-white glow that is a characteristic of B-type stars.[12]

It is spinning rapidly, with a projected rotational velocity of 255 km/s [9] 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.[13]

Naming[edit]

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.)[14]

References[edit]

  1. ^ a b c d e f 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. ^ a b c d 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. ^ a b 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. ^ a b 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, Determination of Radial Velocities and their Applications, Proceedings from IAU Symposium no. 30, University of Toronto: International Astronomical Union, Bibcode:1967IAUS...30...57E. 
  6. ^ a b c d e f 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. 
  7. ^ a b 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. 
  8. ^ a b 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. 
  9. ^ a b 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. 
  10. ^ 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. 
  11. ^ "eps Aps -- Be Star", SIMBAD (Centre de Données astronomiques de Strasbourg), retrieved 2012-07-08. 
  12. ^ "The Colour of Stars", Australia Telescope, Outreach and Education (Commonwealth Scientific and Industrial Research Organisation), December 21, 2004, retrieved 2012-01-16. 
  13. ^ Samus, N. N.; Durlevich, O. V.; Kazarovets, R. V., "eps Aps", General Catalogue of Variable Stars (Sternberg Astronomical Institute), retrieved 2012-07-09. 
  14. ^ (Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 29 日

External links[edit]