Beta Lupi

Beta Lupi (β Lupi, β Lup), or Kekouan /ˈkɛkwɑːn/, is a star in the southern constellation of Lupus. It has an apparent visual magnitude of 2.7,[2] making it readily visible to the naked eye. Based upon parallax measurements, this star is located at a distance of about 383 light-years (117 parsecs) from Earth.[2]

Beta Lupus
Location of β Lupus (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Lupus
Right ascension 14h 58m 31.92536s[1]
Declination −43° 08′ 02.2699″[1]
Apparent magnitude (V) 2.68[2]
Characteristics
Spectral type B2 III[3]
U−B color index −0.902[4]
B−V color index −0.226[4]
Variable type β Cep[5]
Astrometry
Radial velocity (Rv)+0.1 ± 1.0[3] km/s
Proper motion (μ) RA: −35.78[1] mas/yr
Dec.: −39.83[1] mas/yr
Parallax (π)8.52 ± 0.18[1] mas
Distance383 ± 8 ly
(117 ± 2 pc)
Absolute magnitude (MV)−3.3[6]
Details
Mass8.8 ± 0.2[7] M☉
Radius6.6[8] R☉
Luminosity10,000[6] L☉
Surface gravity (log g)3.76[6] cgs
Temperature24,090[9] K
Metallicity [Fe/H]−0.35 ± 0.11[5] dex
Rotational velocity (v sin i)92[3] km/s
Age24.6 ± 2.7[7] Myr
Other designations
Kekouan, CD−42° 9853, FK5 552, HD 132058, HIP 73273 , HR 5571, SAO 225335.[10]
Database references
SIMBADdata

Properties

The stellar classification of B2 III indicates this is a giant star.[3] The effective temperature of the star's outer envelope is 24,090 K,[9] giving it the blue-white hue of a B-type star.[11] With an age of around 25 million years,[7] it is near the end of its hydrogen phase, where hydrogen is fused into the element helium, and transferring into a red supergiant star. At about 8.8[7] solar masses, it may have enough mass to end its life as a Type II supernova, but there is the possibility of Beta Lupi becoming a white dwarf.[12]

This is a multi-period Beta Cephei variable with a dominant oscillation period of 0.232 days.[5] It 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.[6] Beta Lupi has a high proper motion of more than 50 mas per year, suggesting a significant transverse velocity.[13]

It lies close to the supernova remnant SN 1006.

Name

In Chinese, 騎官 (Qí Guān), meaning Imperial Guards, refers to an asterism consisting of β Lupi, γ Lupi, δ Lupi, κ Centauri, λ Lupi, ε Lupi, μ Lup, π Lupi, ο Lupi and α Lupi.[14] Consequently, the Chinese name for β Lupi itself is 騎官四 (Qí Guān sì, English: the Fourth Star of Imperial Guards.).[15] From the French rendering of this Chinese name derives the traditional European name Kekouan (Ke Kwan).[16]

See also

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. Wielen, R.; et al. (1999), Sixth Catalogue of Fundamental Stars (FK6). Part I. Basic fundamental stars with direct solutions, Astronomisches Rechen-Institut Heidelberg, Bibcode:1999VeARI..35....1W
  3. Jilinski, E.; et al. (March 2006), "Radial velocity measurements of B stars in the Scorpius-Centaurus association", Astronomy and Astrophysics, 448 (3): 1001–1006, arXiv:astro-ph/0601643, Bibcode:2006A&A...448.1001J, doi:10.1051/0004-6361:20041614
  4. 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
  5. Daszyńska-Daszkiewicz, J.; Niemczura, E. (April 2005), "Metallicity of mono- and multiperiodic β Cephei stars", Astronomy and Astrophysics, 433 (3): 1031–1035, arXiv:astro-ph/0410442, Bibcode:2005A&A...433.1031D, doi:10.1051/0004-6361:20040397
  6. 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
  7. 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
  8. Underhill, A. B.; et al. (November 1979), "Effective temperatures, angular diameters, distances and linear radii for 160 O and B stars", Monthly Notices of the Royal Astronomical Society, 189: 601–605, Bibcode:1979MNRAS.189..601U, doi:10.1093/mnras/189.3.601
  9. Zorec, J.; et al. (July 2009), "Fundamental parameters of B supergiants from the BCD system. I. Calibration of the (λ_1, D) parameters into Teff", Astronomy and Astrophysics, 501 (1): 297–320, arXiv:0903.5134, Bibcode:2009A&A...501..297Z, doi:10.1051/0004-6361/200811147
  10. "bet Lup -- Variable Star", SIMBAD, Centre de Données astronomiques de Strasbourg, retrieved 2012-01-16
  11. "The Colour of Stars", Australia Telescope, Outreach and Education, Commonwealth Scientific and Industrial Research Organisation, December 21, 2004, archived from the original on 2012-03-10, retrieved 2012-01-16
  12. Kaler, James B. (2007), "Beta Lupi", Stars, University of Illinois, archived from the original on 2011-07-16, retrieved 2009-07-03
  13. Jiménez-Esteban, F. M.; Caballero, J. A.; Solano, E. (January 2011), "Identification of blue high proper motion objects in the Tycho-2 and 2MASS catalogues using Virtual Observatory tools", Astronomy and Astrophysics, 525: A29, arXiv:1009.3466, Bibcode:2011A&A...525A..29J, doi:10.1051/0004-6361/201015223
  14. (in Chinese) 中國星座神話, written by 陳久金. Published by 台灣書房出版有限公司, 2005, ISBN 978-986-7332-25-7.
  15. (in Chinese) 香港太空館 - 研究資源 - 亮星中英對照表 Archived 2011-01-29 at the Wayback Machine, Hong Kong Space Museum. Accessed on line November 23, 2010.]
  16. Richard Hinckley Allen: Star Names — Their Lore and Meaning: Lupus
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