γ Boötis
(Seginus system)
Location of γ Boötis (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Boötes
Right ascension 14h 32m 04.67180s[1]
Declination +38° 18′ 29.7043″[1]
Apparent magnitude (V) +3.03[2]
+3.02 to +3.07[3]
Characteristics
Spectral type A7 IV+(n)[2] or A7 III[4]
U−B color index +0.120[4]
B−V color index +0.191[4]
Variable type δ Sct[5]
Astrometry
Radial velocity (Rv)−32.40±1.0[6] km/s
Proper motion (μ) RA: −115.71[1] mas/yr
Dec.: +151.16[1] mas/yr
Parallax (π)37.58 ± 0.14 mas[1]
Distance86.8 ± 0.3 ly
(26.61 ± 0.10 pc)
Absolute magnitude (MV)+0.93[4]
Details
Aa
Mass2.10[7] M☉
Radius5.16+0.71
−0.96[8] R☉
Luminosity33.4[9] L☉
Surface gravity (log g)3.75±0.05[4] cgs
Temperature7,800[10] K
Metallicity [Fe/H]−0.08[4] dex
Rotational velocity (v sin i)121[10] km/s
Age0.9[4] or 1.0[7] Gyr
Other designations
Seginus, Haris, Ceginus, Segin, Gam Boo, 27 Boötis, BD+38°2565, FK5 535, HD 127762, HIP 71075, HR 5435, SAO 64203, WDS J14321+3818A, BU 616[11]
Database references
SIMBADdata

Gamma Boötis, Latinised from γ Boötis, is a binary star[12] system in the northern constellation of Boötes the herdsman, forming the left shoulder of this asterism.[13] The primary component has the proper name Seginus /sɪˈdʒaɪnəs/, the traditional name of the Gamma Bootis system.[14] It has a white hue and is visible to the naked eye with a typical apparent visual magnitude of +3.03.[2] Based on parallax measurements obtained during the Hipparcos mission, it is located at a distance of approximately 85 light-years from the Sun, but is drifting closer with a radial velocity of −32 km/s.[6]

Properties

The double nature of this system was discovered by American astronomer S. W. Burnham in 1878, and has the discovery code BU 616.[15] The system is resolved into a pair separated by 33.4 arcseconds with a magnitude difference of 9.27. The brighter primary is itself a close pair separated by 0.069″,[16] as discovered by B. L. Morgan and associates in 1975.[15] The primary or 'A' component of this double star system is designated WDS J14321+3818 ('B' is the star UCAC2 45176266[17]) in the Washington Double Star Catalog. Parallax measurements for component B give a distance of approximately 1,996 light-years.[18] Gamma Boötis' two components are themselves designated WDS J14321+3818Aa (Seginus)[14] and Ab.

A light curve for Gamma Boötis, plotted from TESS data[19]

The stellar classification of Gamma Boötis is A7IV+(n),[2] matching an A-type star with somewhat "nebulous" lines due to rapid rotation. It was found to be a short-period variable star in 1914 by German astronomers P. Guthnick and R. Prager. Non-radial pulsations were detected in 1992 by Edward J. Kennelly and colleagues.[10] It is a Delta Scuti-type variable star with a period of 6.96753 h that varies from magnitude +3.02 down to +3.07.[3] This dominant mode is 21.28 cycles per day with an amplitude of 0.05 in magnitude.[10] Additional pulsations occur at 18.09, 12.02, 11.70 and 5.06 cycles per day.[4]

These types of stars are usually on the main sequence or slightly evolved.[4] The primary is around one billion years old with 2.1[7] times the mass of the Sun and five[8] times the Sun's radius. Measurements of the projected rotational velocity range from 115 to 145 km/s,[4] suggesting a high rate of spin. On average, the star is radiating 33.4[9] times the luminosity of the Sun from its photosphere at an effective temperature of 7,800 K.[10]

The system displays a statistically significant infrared excess due to a circumstellar disk. A model fit to the data indicates this material has a mean temperature of 85 K and is orbiting at a distance of 99±10 AU.[9]

Nomenclature

γ Boötis (Latinised to Gamma Boötis) is the binary's Bayer designation. WDS J14321+3818 is the wider system's designation in the Washington Double Star Catalog. The designations of the two constituents as WDS J14321+3818A and B, and those of A's components—WDS J14321+3818Aa and Ab—derive from the convention used by the Washington Multiplicity Catalog (WMC) for multiple star systems, and adopted by the International Astronomical Union (IAU).[20]

Gamma Boötis bore the traditional name Ceginus (later Seginus), from cheguius or theguius, apparently Latin mistranscriptions of an Arabic rendering of Greek Boötes.[21] Two possibilities have been suggested: from Arabic بوطس bwṭs, in one of the manuscripts of the Almagest, with undotted ب b mistaken for an undotted ث th, و w taken as w and spelled 'gu', and ط ṭ completely misread,[22] or from Arabic بؤوتس bwʾwts, with undotted ب b mistaken for an undotted ث th, ؤ w-hamza mistaken for غ ġ, و w read as u, and undotted ن n misread as an undotted ى y and transcribed i—that is, as th-g-u-i-s with unwritten vowels (and the Latin grammatical ending -us) filled in for theguius.[23]

In 2016, the IAU organized a Working Group on Star Names (WGSN)[24] to catalogue and standardize proper names for stars. The WGSN decided to attribute proper names to individual stars rather than entire multiple systems.[25] It approved the name Seginus for WDS J14321+3818Aa on 21 August 2016 and it is now so included in the List of IAU-approved Star Names.[14]

Gamma Boötis was listed as Haris in Bečvář, apparently derived from the Arabic name of the constellation of Boötes, Al-Haris Al-Sama meaning "the guard of the north".[21]

In the catalogue of stars in the Calendarium of Al Achsasi al Mouakket, this star was designated Menkib al Aoua al Aisr (منكب العواء الأيسر – mankibu lʿawwaaʾi lʾaysar), which was translated into Latin as Humerus Sinister Latratoris, meaning 'the left shoulder of barker'.[26]

In Chinese astronomy, Gamma Boötis is called 招搖, Pinyin: Zhāoyáo, meaning Twinkling Indicator, because this star is marking itself and standing alone in Twinkling Indicator asterism, Root mansion (see: Chinese constellation).[27] 招搖 (Zhāoyáo), westernized into Chaou Yaou, but the name Chaou Yaou was designated for Beta Boötis (Nekkar) by R.H. Allen and the meaning is "to beckon, excite, or move."[13]

Namesake

USS Seginus (AK-133) was a U.S. Navy Crater-class cargo ship named after the star.

References

  1. 1 2 3 4 5 van Leeuwen, F. (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. 1 2 3 4 Gray, R. O.; et al. (April 2001), "The Physical Basis of Luminosity Classification in the Late A-, F-, and Early G-Type Stars. I. Precise Spectral Types for 372 Stars", The Astronomical Journal, 121 (4): 2148–2158, Bibcode:2001AJ....121.2148G, doi:10.1086/319956.
  3. 1 2 Samus', N. N; Kazarovets, E. V; Durlevich, O. V; Kireeva, N. N; Pastukhova, E. N (2017), "General catalogue of variable stars: Version GCVS 5.1", Astronomy Reports, 61 (1): 80, Bibcode:2017ARep...61...80S, doi:10.1134/S1063772917010085, S2CID 125853869.
  4. 1 2 3 4 5 6 7 8 9 10 Ventura, R.; et al. (November 2007), "A spectroscopic search for non-radial pulsations in the δ Scuti star γ Bootis", Monthly Notices of the Royal Astronomical Society, 381 (4): 1647–1654, arXiv:0708.2364, Bibcode:2007MNRAS.381.1647V, doi:10.1111/j.1365-2966.2007.12334.x, S2CID 14915070.
  5. ↑ 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.
  6. 1 2 Gontcharov, G. A. (2006), "Pulkovo Compilation of Radial Velocities for 35 495 Hipparcos stars in a common system", Astronomy Letters, 32 (11): 759–771, arXiv:1606.08053, Bibcode:2006AstL...32..759G, doi:10.1134/S1063773706110065, S2CID 119231169.
  7. 1 2 3 De Rosa, R. J.; et al. (2014), "The VAST Survey - III. The multiplicity of A-type stars within 75 pc", Monthly Notices of the Royal Astronomical Society, 437 (2): 1216–1240, arXiv:1311.7141, Bibcode:2014MNRAS.437.1216D, doi:10.1093/mnras/stt1932.
  8. 1 2 Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
  9. 1 2 3 Yelverton, Ben; et al. (September 2019), "A statistically significant lack of debris discs in medium separation binary systems", Monthly Notices of the Royal Astronomical Society, 488 (3): 3588–3606, arXiv:1907.04800, Bibcode:2019MNRAS.488.3588Y, doi:10.1093/mnras/stz1927.
  10. 1 2 3 4 5 Fossati, L.; et al. (July 2008), "Abundance analysis of seven δ Scuti stars", Astronomy and Astrophysics, 485 (1): 257–265, arXiv:0804.2402, Bibcode:2008A&A...485..257F, doi:10.1051/0004-6361:200809541, S2CID 8543459.
  11. ↑ "gam Boo", SIMBAD, Centre de données astronomiques de Strasbourg, retrieved 2016-12-18.
  12. ↑ 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.
  13. 1 2 Allen, Richard Hinckley (1963), Star Names: Their Lore and Meaning (Dover ed.), retrieved 2020-12-30.
  14. 1 2 3 Naming Stars, IAU.org, retrieved 18 June 2018.
  15. 1 2 Mason, Brian D.; et al. (December 2001), "The 2001 US Naval Observatory Double Star CD-ROM. I. The Washington Double Star Catalog", The Astronomical Journal, United States Naval Observatory, 122 (6): 3466–3471, Bibcode:2001AJ....122.3466M, doi:10.1086/323920, retrieved 2020-12-30.
  16. ↑ Morgan, B. L.; et al. (June 1978), "Observations of binary stars by speckle interferometry - I.", Monthly Notices of the Royal Astronomical Society, 183 (4): 701–710, Bibcode:1978MNRAS.183..701M, doi:10.1093/mnras/183.4.701.
  17. ↑ "UCAC2 45176266", SIMBAD, Centre de données astronomiques de Strasbourg, retrieved 2018-07-24.
  18. ↑ Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
  19. ↑ MAST: Barbara A. Mikulski Archive for Space Telescopes, Space Telescope Science Institute, retrieved 8 December 2021.
  20. ↑ Hessman, F. V.; et al. (2010), On the naming convention used for multiple star systems and extrasolar planets, arXiv:1012.0707, Bibcode:2010arXiv1012.0707H, 1012.0707.
  21. 1 2 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 Pubublishing Company, ISBN 978-1-931559-44-7.
  22. ↑ Kunitzsch, Paul (1959), Arabische sternnamen in europa, pp. 152–153.
  23. ↑ Laffitte, Roland (2001), Héritages arabes des noms arabes pour les étoiles, p. 160.
  24. ↑ IAU working group on star names (WGSN), IAU, retrieved 22 May 2016.
  25. ↑ WG Triennial Report (2015-2018) - Star Names (PDF), p. 5, retrieved 2018-07-14.
  26. ↑ Knobel, E. B. (June 1895), "Al Achsasi Al Mouakket, on a catalogue of stars in the Calendarium of Mohammad Al Achsasi Al Mouakket", Monthly Notices of the Royal Astronomical Society, 55: 429, Bibcode:1895MNRAS..55..429K, doi:10.1093/mnras/55.8.429.
  27. ↑ (in Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 6 月 29 日
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