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Eta Centauri

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Not to be confused with H Centauri.
Eta Centauri
Location of ηいーた Centauri (circled)
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Centaurus
Right ascension 14h 35m 30.42416s[1]
Declination −42° 09′ 28.1708″[1]
Apparent magnitude (V) +2.35[2] (2.30 - 2.41[3])
Characteristics
Spectral type B1.5 Vne[4]
U−B color index −0.862[2]
B−V color index −0.215[2]
Variable type GCAS[3] + LERI
Astrometry
Radial velocity (Rv)−0.2[5] km/s
Proper motion (μみゅー) RA: −34.73[1] mas/yr
Dec.: −32.72[1] mas/yr
Parallax (πぱい)10.67 ± 0.21 mas[1]
Distance306 ± 6 ly
(94 ± 2 pc)
Absolute magnitude (MV)−2.53[6]
Details
Mass12.0±0.3[7] M☉
Radius6.10±0.12[8] R☉
Luminosity8,700[4] L☉
Surface gravity (log g)3.95±0.04[8] cgs
Temperature25,700[4] K
Rotational velocity (v sin i)330[4] km/s
Age5.6±1.0[7] Myr
Other designations
ηいーた Cen, CD−41°8917, CPD−41°6839, FK5 537, HD 127972, HIP 71352, HR 5440, SAO 225044.[9]
Database references
SIMBADdata

Eta Centauri, Latinized from ηいーた Centauri, is a star in the southern constellation of Centaurus. It has an apparent visual magnitude of +2.35[2] and is located at a distance of around 306 light-years (94 parsecs).[1]

A light curve for Eta Centauri, plotted from TESS data[10]

The stellar classification of this star is B1.5 Vne,[4] indicating that it is a B-type main sequence star. The 'n' suffix means that the absorption lines are broadened from rapid rotation and the 'e' that it shows emission lines in its spectrum. It has a projected rotational velocity of 330 km s−1[4] and completes a full rotation in less than a day.

As a Be star,[11] it has variable emissions in its hydrogen spectral lines. This emission can be modelled by a decretion disk of gas that has been ejected from the star by its rapid rotation and now follows a near-Keplerian orbit around the central body.[12] Its brightness is also slightly variable, and it is classified as a Gamma Cassiopeiae variable star with multiple periods of variability.[3] The International Variable Star Index lists Eta Centauri as both a Gamma Cassiopeiae variable and a Lambda Eridani variable with variations caused by its rotation and pulsations.[13]

Eta Centauri has about 12 times the mass of the Sun,[7] placing it above the dividing line between stars that evolve into white dwarfs and those that turn into supernovae. It is radiating 8,700[4] times the luminosity of the Sun from its outer atmosphere at an effective temperature of 25,700 K.[4] At this temperature, the star glows with the blue-white hue common to B-type stars.[14] Eta Centauri is a proper motion member of the Upper Centaurus–Lupus sub-group in the Scorpius–Centaurus OB association, the nearest such co-moving association of massive stars to the Sun.[15]

In traditional Chinese astronomy, Eta Centauri was known as 庫くら樓ろう二に[16] (meaning: the Second (Star) of Koo Low).[17]

References

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  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, S2CID 18759600.
  2. ^ a b c d Gutierrez-Moreno, Adelina; Moreno, Hugo (June 1968), "A photometric investigation of the Scorpio-Centaurus association", Astrophysical Journal Supplement Series, 15: 459, Bibcode:1968ApJS...15..459G, doi:10.1086/190168.
  3. ^ a b c Samus, N. N.; Durlevich, O. V.; et al. (2009), "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007–2013)", VizieR On-line Data Catalog: B/gcvs, 1: 02025, Bibcode:2009yCat....102025S.
  4. ^ a b c d e f g h Balona, L. A.; Dziembowski, W. A. (October 1999), "Excitation and visibility of high-degree modes in stars", Monthly Notices of the Royal Astronomical Society, 309 (1): 221–232, Bibcode:1999MNRAS.309..221B, doi:10.1046/j.1365-8711.1999.02821.x.
  5. ^ Wielen, R.; et al. (1999), "Sixth Catalogue of Fundamental Stars (FK6). Part I. Basic fundamental stars with direct solutions", Veröff. Astron. Rechen-Inst. Heidelb, 35 (35), Astronomisches Rechen-Institut Heidelberg: 1, Bibcode:1999VeARI..35....1W.
  6. ^ 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.
  7. ^ a b c 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, S2CID 118629873.
  8. ^ a b Arcos, C.; et al. (March 2018), "Stellar parameters and H αあるふぁ line profile variability of Be stars in the BeSOS survey", Monthly Notices of the Royal Astronomical Society, 474 (4): 5287–5299, arXiv:1711.08675, Bibcode:2018MNRAS.474.5287A, doi:10.1093/mnras/stx3075.
  9. ^ "eta Cen", SIMBAD, Centre de données astronomiques de Strasbourg, retrieved 2012-03-03.
  10. ^ MAST: Barbara A. Mikulski Archive for Space Telescopes, Space Telescope Science Institute, retrieved 8 December 2021.
  11. ^ Janot-Pacheco, E., Leister NV, et al. (1999), "Multi-periodicity of the Be star ηいーた Centauri from spectroscopic and photometric observations", Astronomy and Astrophysics Supplement Series, 137 (3): 407, Bibcode:1999A&AS..137..407J, doi:10.1051/aas:1999256.
  12. ^ Silaj, J.; Jones, C. E.; Tycner, C.; Sigut, T. A. A.; Smith, A. D. (March 2010), "A Systematic Study of Hαあるふぁ Profiles of Be Stars", Astrophysical Journal Supplement Series, 187 (1): 228–250, Bibcode:2010ApJS..187..228S, doi:10.1088/0067-0049/187/1/228, S2CID 122679154.
  13. ^ Watson, C. L. (2006), "The International Variable Star Index (VSX)", The Society for Astronomical Sciences 25th Annual Symposium on Telescope Science. Held May 23–25, 25: 47, Bibcode:2006SASS...25...47W.
  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. ^ de Geus, E. J.; de Zeeuw, P. T.; Lub, J. (June 1989), "Physical parameters of stars in the Scorpio-Centaurus OB association", Astronomy and Astrophysics, 216 (1–2): 44–61, Bibcode:1989A&A...216...44D.
  16. ^ (in Chinese) 中國ちゅうごく星座せいざ神話しんわ, written by 陳ひね久金ひさがね. Published by 台灣たいわん書房しょぼう出版しゅっぱん有限ゆうげん公司こうし, 2005, ISBN 978-986-7332-25-7.
  17. ^ Allen, R. H. (1963), Star Names: Their Lore and Meaning (Reprint ed.), New York, NY: Dover Publications Inc., p. 154, ISBN 0-486-21079-0.
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