Kappa Scorpii

Kappa Scorpii, Latinized from κ Scorpii, is a binary star system in the southern constellation of Scorpius. With an apparent visual magnitude of 2.4, this star system is readily visible to the naked eye. Parallax measurements place it at an estimated distance of roughly 480 light-years (150 parsecs) from the Earth.

κ Scorpii
Location of κ Sco (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Scorpius
Right ascension 17h 42m 29.27520s[1]
Declination −39° 01′ 47.9391″[1]
Apparent magnitude (V) 2.41 - 2.42[2]
Characteristics
Spectral type B1.5 III[3]
U−B color index −0.914[4]
B−V color index −0.228[4]
Variable type β Cephei[2]
Astrometry
Radial velocity (Rv)−14.0[5] km/s
Proper motion (μ) RA: −6.05[1] mas/yr
Dec.: −25.54[1] mas/yr
Parallax (π)6.75 ± 0.17 mas[1]
Distance480 ± 10 ly
(148 ± 4 pc)
Absolute magnitude (MV)−3.46[6]
Orbit[7]
Period (P)195.65 days
Eccentricity (e)0.488±0.005
Periastron epoch (T)92.7±0.5
Semi-amplitude (K1)
(primary)		48.0±0.3 km/s
Details
κ Sco A
Mass17[7] M☉
Radius6.8[7] R☉
Luminosity6,911[6] L☉
Surface gravity (log g)4.01[7] cgs
Temperature23,400[7] K
Rotation1.90 days[7]
Rotational velocity (v sin i)105[8] km/s
Age25.1±1.3[9] Myr
κ Sco B
Mass12[7] M☉
Radius5.8[7] R☉
Surface gravity (log g)4.00[7] cgs
Temperature18,800[7] K
Other designations
Girtab, κ Sco, CD−38°12137, CPD−38°6992, FK5 660, HD 160578, HIP 86670, HR 6580, SAO 209163
Database references
SIMBADdata

Properties

This is a spectroscopic binary, which is a type of binary star system in which the two stars are so close together that they have not been individually resolved with a telescope. The pair orbit each other with a period of about 196 days and an eccentricity of nearly 0.5.[7] The combined spectrum of this pair matches a star with a stellar classification of B1.5 III.[3] The 'III' luminosity class indicates the presence of a giant star that has exhausted the supply of hydrogen at its core and is in a late evolutionary stage.

A light curve for Kappa Scorpii, adapted from Lomb and Shobbrook (1975)[10]

The primary component of the pair, κ Sco A, is a variable star of Beta Cephei type. It is undergoing radial pulsations with a dominant frequency of 4.99922 cycles per day, or 4.8 hours per cycle. There are overlapping secondary pulsation frequencies of about 4.85 and 5.69 cycles per day.[11] This star has about 17 times the mass of the Sun and is nearly 7 times the Sun's radius.[7] The effective temperature of the outer envelope is 23,400 K,[7] giving it a blue-white hue. It is rotating rapidly, with an estimated period of only 1.9 days and an axis of rotation that is inclined by about 40° to the line of sight from the Earth.[7]

The secondary component, κ Sco B, is smaller than the primary, but still much larger than the Sun. It has about 12 times the mass of the Sun and nearly six times the Sun's radius.[7] The effective temperature of 18,800 K[7] is also higher than the Sun's, which is at 5,778 K.

Traditional name

κ Scorpii has been called Girtab /ˈɡɜːrtæb/,[12] which is the Sumerian word for 'scorpion'. The name has survived through the Babylonian star catalogues,[13] and was originally applied to an asterism comprising this star, Lambda Scorpii, Upsilon Scorpii, and Iota Scorpii.[12]

In Chinese, 尾宿 (Wěi Xiù), meaning Tail, refers to an asterism consisting κ Scorpii, μ1 Scorpii, ε Scorpii, ζ1 Scorpii and ζ2 Scorpii, η Scorpii, θ Scorpii, ι1 Scorpii and ι2 Scorpii, λ Scorpii and υ Scorpii.[14] Consequently, the Chinese name for κ Scorpii itself is 尾宿七 (Wěi Xiù qī), "the Seventh Star of Tail".[15]

Modern legacy

κ Scorpii appears on the flag of Brazil, symbolising the state of Paraíba.[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, S2CID 18759600
  2. Samus, N. N.; et al. (2017). "General Catalogue of Variable Stars". Astronomy Reports. 5.1. 61 (1): 80–88. Bibcode:2017ARep...61...80S. doi:10.1134/S1063772917010085. S2CID 125853869.
  3. Houk, Nancy (1978), "Michigan catalogue of two-dimensional spectral types for the HD star", Michigan Catalogue of Two-dimensional Spectral Types for the HD Stars. Volume 3. Declinations -40.0° to -26.0°, Ann Arbor: Dept. of Astronomy, University of Michigan: distributed by University Microfilms International, 3, Bibcode:1982mcts.book.....H
  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. Wielen, R.; et al. (1999), "Sixth Catalogue of Fundamental Stars (FK6). Part I. Basic fundamental stars with direct solutions", Veröff. Astron. Rechen-Inst. Heidelb, Astronomisches Rechen-Institut Heidelberg, 35 (35): 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. Uytterhoeven, K.; et al. (June 2001), "Line-profile variations of the double-lined spectroscopic binary kappa Scorpii", Astronomy and Astrophysics, 371 (3): 1035–1047, Bibcode:2001A&A...371.1035U, doi:10.1051/0004-6361:20010456
  8. Bernacca, P. L.; Perinotto, M. (1970), "A Catalogue of Stellar Rotational Velocities", Contributi Osservatorio Astronomico di Padova in Asiago, 239 (1): 1, Bibcode:1970CoAsi.239....1B
  9. 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
  10. Lomb, N. R.; Shobbrook, R. R. (December 1975). "New radial velocities and further photometric observations of lambda Sco and kappa Sco". Monthly Notices of the Royal Astronomical Society. 173: 709–728. Bibcode:1975MNRAS.173..709L. doi:10.1093/mnras/173.3.709. Retrieved 18 August 2022.
  11. Uytterhoeven, K.; et al. (March 2005), "Disentangling component spectra of κ Scorpii, a spectroscopic binary with a pulsating primary. II. Interpretation of the line-profile variability", Astronomy and Astrophysics, 432 (3): 955–967, Bibcode:2005A&A...432..955U, doi:10.1051/0004-6361:20041444
  12. Falkner, David E. (2011), The Mythology of the Night Sky: An Amateur Astronomer's Guide to the Ancient Greek and Roman Legends, Patrick Moore's Practical Astronomy, Springer, p. 106, ISBN 978-1-4614-0136-0
  13. Ridpath, Ian (1989), Star tales, James Clarke & Co., p. 114, ISBN 0-7188-2695-7
  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 2008-10-25 at the Wayback Machine, Hong Kong Space Museum. Accessed on line November 23, 2010.
  16. "Astronomy of the Brazilian Flag". FOTW Flags Of The World website.
  • Kaler, James B., "Kappa Sco", Stars, University of Illinois, retrieved 2014-02-18
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