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Beta Draconis

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Beta Draconis, a name Latinized from β Draconis, is a binary star system[10] and the third-brightest star in the northern circumpolar constellation of Draco. The two components are designated Beta Draconis A (officially named Rastaban /ˈræstəbæn/, “head to sole of foot”, the traditional name of the system)[11] and B respectively. With a combined apparent visual magnitude of 2.79,[2] it is bright enough to be easily seen with the naked eye. Based upon parallax measurements from the Hipparcos astrometry satellite,[12][13] it lies at a distance of about 380 light-years (120 parsecs) from the Sun.[1] The system is drifting closer with a radial velocity of −21 km/s.[4]

β Draconis
Location of β Draconis (circled)
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Draco
Right ascension 17h 30m 25.96170s[1]
Declination +52° 18′ 04.9993″[1]
Apparent magnitude (V) 2.79[2]
Characteristics
Spectral type G2Ib-IIa[3]
U−B color index +0.954±0.007[4]
B−V color index +0.98[5]
R−I color index +0.48[5]
Astrometry
Radial velocity (Rv)−21.00±0.23[4] km/s
Proper motion (μ) RA: −15.89[1] mas/yr
Dec.: +12.28[1] mas/yr
Parallax (π)8.58 ± 0.10 mas[1]
Distance380 ± 4 ly
(117 ± 1 pc)
Absolute magnitude (MV)–2.457[6]
Details
Mass6.0±0.2[2] M☉
Radius40[7] R☉
Luminosity996[7] L☉
Surface gravity (log g)1.86±0.04[8] cgs
Temperature5,160±150[8] K
Metallicity [Fe/H]0.02±0.10[8] dex
Rotational velocity (v sin i)10.7[8] km/s
Age65[2] Myr
Other designations
Rastaban, Rastaben, Alwaid, Asuia, NGCA-V25, β Dra, 23 Dra, BD+52°2065, FK5 653, HD 159181, HIP 85670, HR 6536, SAO 30429, ADS 10611, WDS 17304+5218AB[9]
Database references
SIMBADdata

The binary system consists of a bright giant orbited by a dwarf companion once every four millennia or so.[14] The companion is about 11 magnitudes fainter than the primary star,[15] and the two are separated by 4.2″.[10]

The spectrum of the primary, Beta Draconis A, matches a stellar classification of G2Ib-IIa,[3] showing mixed features of a bright giant and a supergiant star, and is listed as a standard star for that spectral class.[16] It is about 65 million years old[2] and is currently undergoing its first convective dredge-up.[17] Compared to the Sun, Beta Draconis A is an enormous star with six times the mass and roughly 40 times the radius. At this size, it is emitting about 950 times the luminosity of the Sun from its outer envelope at an effective temperature of 5,160 K,[2] giving it the yellow hue of a G-type star.[18] The star has a particularly strong chromospheric emission that is generating X-ray[19][20] and far-UV radiation.[21] There is a detectable magnetic field with a longitudinal field strength of −1.16±0.25 G.[22]

Beta Draconis lies on or near the cepheid instability strip,[23] yet only appears to be a microvariable with a range of about 1/100th of a magnitude.[24][25] It was confirmed as a variable star with a range of about 1/100th of a magnitude by Gabriel Cristian Neagu using data from the TESS and Hipparcos missions.[24][25] The variability was reported to the AAVSO (American Association of Variable Star Observers), in the Variable Star Index.[26]

Nomenclature

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β Draconis (Latinised to Beta Draconis) is the system's Bayer designation. The designations of the two components as Beta Draconis A and B derive from the convention used by the Washington Multiplicity Catalog (WMC) for multiple star systems, and adopted by the International Astronomical Union (IAU).[27]

It bore the traditional name Rastaban, which has also been used for Gamma Draconis.[14][28] This name, less commonly written Rastaben, derives from the Arabic phrase ra's ath-thu'ban "head of the serpent/dragon". It was also known as Asuia and Alwaid /ælˈweɪd/,[29] the latter from the Arabic al-ʽawāʼidh "the old mother camels".[29] In 2016, the IAU organized a Working Group on Star Names (WGSN)[30] to catalogue and standardize proper names for stars. The WGSN approved the name Rastaban for the component Beta Draconis A on 21 August 2016 and it is now so included in the List of IAU-approved Star Names.[11]

Beta Draconis is part of the asterism of the Mother Camels (Arabic al'awa'id), along with Gamma Draconis (Eltanin), Mu Draconis (Erakis), Nu Draconis (Kuma) and Xi Draconis (Grumium), which was later known as the Quinque Dromedarii.[28]

In Chinese, 天棓 (Tiān Bàng), meaning Celestial Flail, refers to an asterism consisting of Beta Draconis, Xi Draconis, Nu Draconis, Gamma Draconis and Iota Herculis.[31] Consequently, the Chinese name for Beta Draconis itself is known as 天棓三 (Tiān Bàng sān, English: the Third Star of Celestial Flail).[28][32][33]

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 e f Lyubimkov, Leonid S.; et al. (February 2010). "Accurate fundamental parameters for A-, F- and G-type Supergiants in the solar neighbourhood". Monthly Notices of the Royal Astronomical Society. 402 (2): 1369–1379. arXiv:0911.1335. Bibcode:2010MNRAS.402.1369L. doi:10.1111/j.1365-2966.2009.15979.x. S2CID 119096173.
  3. ^ a b Keenan, P. C.; Pitts, R. E. (1980). "Revised MK spectral types for G, K and M stars". The Astrophysical Journal Supplement Series. 42: 541. Bibcode:1980ApJS...42..541K. doi:10.1086/190662.
  4. ^ a b c 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.
  5. ^ a b Hoffleit, D.; Warren, Jr., W. H. "HR 6536, database entry". The Bright Star Catalogue (5th Revised ed.). CDS. Retrieved September 17, 2008. ID V/50.
  6. ^ Katz, D.; Soubiran, C.; Cayrel, R.; Barbuy, B.; Friel, E.; Bienaymé, O.; Perrin, M. -N. (2011). "Probing the Galactic thick disc vertical properties and interfaces". Astronomy and Astrophysics. 525: A90. Bibcode:2011A&A...525A..90K. doi:10.1051/0004-6361/201014840.
  7. ^ a b McDonald, I.; Zijlstra, A. A.; Watson, R. A. (2017). "Fundamental parameters and infrared excesses of Tycho–Gaia stars". Monthly Notices of the Royal Astronomical Society. 471 (1): 770–791. arXiv:1706.02208. Bibcode:2017MNRAS.471..770M. doi:10.1093/mnras/stx1433.
  8. ^ a b c d Marfil, E.; et al. (March 2020). "Stellar atmospheric parameters of FGK-type stars from high-resolution optical and near-infrared CARMENES spectra". Monthly Notices of the Royal Astronomical Society. 492 (4): 5470–5507. arXiv:2001.01495. Bibcode:2020MNRAS.492.5470M. doi:10.1093/mnras/staa058.
  9. ^ "bet Dra". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2021-01-11.
  10. ^ a b Eggleton, P. P.; Tokovinin, A. A. (September 2008). "A catalogue of multiplicity among bright stellar systems". Monthly Notices of the Royal Astronomical Society. 389 (2): 869–879. arXiv:0806.2878. Bibcode:2008MNRAS.389..869E. doi:10.1111/j.1365-2966.2008.13596.x. S2CID 14878976.
  11. ^ a b "Naming Stars". IAU.org. Retrieved 2 March 2018.
  12. ^ Perryman, M. A. C.; et al. (July 1997). "The Hipparcos Catalogue". Astronomy and Astrophysics. 323: L49–L52. Bibcode:1997A&A...323L..49P.
  13. ^ Perryman, Michael (2010). The Making of History's Greatest Star Map. Astronomers’ Universe. Heidelberg: Springer-Verlag. Bibcode:2010mhgs.book.....P. doi:10.1007/978-3-642-11602-5. ISBN 978-3-642-11601-8.
  14. ^ a b Kaler, James B. "RASTABAN (Beta Draconis)". STARS. Retrieved 2021-01-11.
  15. ^ Mason, B. D.; et al. (2014). "The Washington Visual Double Star Catalog". The Astronomical Journal. 122 (6): 3466–3471. Bibcode:2001AJ....122.3466M. doi:10.1086/323920. Retrieved 2015-07-22.
  16. ^ Keenan, Philip C.; McNeil, Raymond C. (1989). "The Perkins catalog of revised MK types for the cooler stars". Astrophysical Journal Supplement Series. 71: 245. Bibcode:1989ApJS...71..245K. doi:10.1086/191373. S2CID 123149047.
  17. ^ Kovtyukh, V. V.; et al. (April 2005). "On the lithium abundance in F-, G-supergiants and its possible correlation with rotation". Kinematika I Fizika Nebesnykh Tel. 21 (2): 141–148. Bibcode:2005KFNT...21..141K.
  18. ^ "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.
  19. ^ Evans, Nancy Remage; et al. (May 2010). "Chandra Observation of Polaris: Census of Low-mass Companions". The Astronomical Journal. 139 (5): 1968–1974. Bibcode:2010AJ....139.1968E. doi:10.1088/0004-6256/139/5/1968.
  20. ^ Skinner, S. L.; Brown, A. (1996). "ASCA X-ray spectra of late-type giants and supergiants: the active G star Beta Draconis (G2Ib - II)". In Pallavicini, Roberto; Dupree, Andrea K. (eds.). Cool stars; stellar systems; and the sun; Proceedings of the 9th Cambridge workshop; held 3-6 October 1995 in Florence; Italy. Astronomical Society of the Pacific Conference Series. Vol. 109. San Francisco: Astronomical Society of the Pacific (ASP). p. 291. Bibcode:1996ASPC..109..291S.
  21. ^ Brown, A.; et al. (August 1984). "High-resolution, far-ultraviolet study of beta Draconis (G2 Ib-II) : transition region structure and energy balance". Astrophysical Journal. 283: 731–744. Bibcode:1984ApJ...283..731B. doi:10.1086/162358.
  22. ^ Grunhut, J. H.; et al. (November 2010). "Systematic detection of magnetic fields in massive, late-type supergiants". Monthly Notices of the Royal Astronomical Society. 408 (4): 2290–2297. arXiv:1006.5891. Bibcode:2010MNRAS.408.2290G. doi:10.1111/j.1365-2966.2010.17275.x. S2CID 118564860.
  23. ^ Butler, R. Paul (February 1998). "A Precision Velocity Study of Photometrically Stable Stars in the Cepheid Instability Strip". The Astrophysical Journal. 494 (1): 342–365. Bibcode:1998ApJ...494..342B. doi:10.1086/305195.
  24. ^ a b Ricker, George R.; et al. (2014). Oschmann, Jacobus M.; Clampin, Mark; Fazio, Giovanni G.; MacEwen, Howard A. (eds.). "Transiting Exoplanet Survey Satellite (TESS)". Space Telescopes and Instrumentation 2014: Optical. Space Telescopes and Instrumentation 2014: Optical, Infrared, and Millimeter Wave. 9143: 914320. arXiv:1406.0151. Bibcode:2014SPIE.9143E..20R. doi:10.1117/12.2063489. hdl:1721.1/97916. S2CID 54001919.
  25. ^ a b ESA (1997). "The HIPPARCOS and TYCHO catalogues. Astrometric and photometric star catalogues derived from the ESA HIPPARCOS Space Astrometry Mission". Esa Special Publication. 1200. ESA. Bibcode:1997ESASP1200.....E.
  26. ^ "bet Dra". The International Variable Star Index. American Association of Variable Star Observers. Retrieved 2020-01-11.
  27. ^ Hessman, F. V.; et al. (December 2010). "On the naming convention used for multiple star systems and extrasolar planets". arXiv:1012.0707 [astro-ph.SR].
  28. ^ a b c Allen, R. H. (1963). Star Names: Their Lore and Meaning (Reprint ed.). New York, NY: Dover Publications Inc. pp. 207–208. ISBN 0-486-21079-0. Retrieved 2010-12-12.
  29. ^ a b Kunitzsch, Paul; Smart, Tim (2006). A Dictionary of Modern star Names: A Short Guide to 254 Star Names and Their Derivations (2nd rev. ed.). Cambridge, Massachusetts: Sky Pub. ISBN 978-1-931559-44-7.
  30. ^ "IAU Working Group on Star Names (WGSN)". International Astronomical Union. Retrieved 22 May 2016.
  31. ^ (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.
  32. ^ (in Chinese) 香港太空館 - 研究資源 - 亮星中英對照表 Archived 2011-01-30 at the Wayback Machine, Hong Kong Space Museum. Accessed on line November 23, 2010.
  33. ^ Wright, Anne. "Alwaid". Constellations of Words. Retrieved September 17, 2008.
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