Gamma Aquarii

Gamma Aquarii
Diagram showing star positions and boundaries of the Aquarius constellation and its surroundings


Location of γ Aquarii (circled)

Observation data
Epoch J2000      Equinox J2000
Constellation Aquarius
Right ascension 22h 21m 39.37542s[1]
Declination –01° 23′ 14.4031″[1]
Apparent magnitude (V) 3.849[2]
Characteristics
Spectral type A0 V[3]
U−B color index –0.092[2]
B−V color index –0.060[2]
Astrometry
Radial velocity (Rv)–15[4] km/s
Proper motion (μ) RA: +129.53[1] mas/yr
Dec.: +7.77[1] mas/yr
Parallax (π)19.92 ± 1.04[1] mas
Distance164 ± 9 ly
(50 ± 3 pc)
Details
Surface gravity (log g)4.0[5] cgs
Temperature10,500[5] K
Metallicity [Fe/H]+0.30[5] dex
Rotational velocity (v sin i)80[6] km/s
Other designations
Sadalachbia, Sadachbia, 48 Aquarii, ADS 15864, BD-02°5741, FK5 842, HD 212061, HIP 110395, HR 8518, SAO 146044.[7]

Gamma Aquarii (γ Aqr, γ Aquarii) is the Bayer designation for a star in the constellation Aquarius. It has the traditional name Sadachbia, from an Arabic expression سعد الأخبية sa‘d al-’axbiyah "luck of the homes (tents)" in Hindu system it is also called Satabhishaj (a hundred physicians) in devnagari, sadhayam in tamil. This star has an apparent visual magnitude of 3.849,[2] making it one of the brighter members of the constellation. Based upon parallax measurements, this star is located at a distance of roughly 164 light-years (50 parsecs) from the Sun, with an error margin of 5%.[1] The star is a spectroscopic binary with a period of 58.1 days.

In the catalogue of stars in the Calendarium of Al Achsasi Al Mouakket, this star was designated Aoul al Achbiya (أول ألأجبية - awwil al ahbiyah), which was translated into Latin as Prima Tabernaculorum, meaning the first of luck of the homes (tents).[8] This star, along with π Aqr (Seat), ζ Aqr (Sadaltager / Achr al Achbiya) and η Aqr (Hydria), were al Aḣbiyah (الأخبية), the Tent.[9][10][11]

In Chinese, 墳墓 (Fén Mù), meaning Tomb, refers to an asterism consisting of γ Aquarii, ζ Aquarii, η Aquarii, π Aquarii.[12] Consequently, γ Aquarii itself is known as 墳墓二 (Fén Mù èr, English: the Second Star of Tomb).[13]

Gamma Aquarii is an A-type main sequence star with a stellar classification of A0 V,[3] making it both larger and more massive than the Sun. It is a candidate Lambda Boötis star, suggesting it may have accreted low-metallicity circumstellar gas some time in the past.[14] It is spinning relatively rapidly with a projected rotational velocity of 80 km s−1.[6] This value gives a lower bound on the actual azimuthal velocity along the star's equator. The outer atmosphere of Gamma Aquarii is radiating energy at an effective temperature of 10,500 K,[5] which is nearly double the temperature at the surface of the Sun. This heat is what gives Gamma Aquarii the white-hot glow of an A-type star.[15]

References

  1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 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. ↑ 2.0 2.1 2.2 2.3 Cousins, A. W. J. (1984), "Standardization of Broadband Photometry of Equatorial Standards", South African Astronomical Observatory Circulars 8: 59, Bibcode:1984SAAOC...8...59C.
  3. ↑ 3.0 3.1 Cowley, A. et al. (April 1969), "A study of the bright A stars. I. A catalogue of spectral classifications", Astronomical Journal 74: 375–406, Bibcode:1969AJ.....74..375C, doi:10.1086/110819.
  4. ↑ Wilson, Ralph Elmer (1953), General Catalogue of Stellar Radial Velocities, Washington: Carnegie Institution of Washington, Bibcode:1953QB901.W495......
  5. ↑ 5.0 5.1 5.2 5.3 Baschek, Bodo; Searle, Leonard (February 1969), "The Chemical Composition of the Lambda Bootis Stars", Astrophysical Journal 155: 537, Bibcode:1969ApJ...155..537B, doi:10.1086/149890.
  6. ↑ 6.0 6.1 Royer, F.; Zorec, J.; Gómez, A. E. (February 2007), "Rotational velocities of A-type stars. III. Velocity distributions", Astronomy and Astrophysics 463 (2): 671–682, arXiv:astro-ph/0610785, Bibcode:2007A&A...463..671R, doi:10.1051/0004-6361:20065224.
  7. ↑ "gam Aqr -- Star in double system", SIMBAD Astronomical Object Database (Centre de Données astronomiques de Strasbourg).
  8. ↑ 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.
  9. ↑ Davis Jr., G. A. (October 1944), "The Pronunciations, Derivations, and Meanings of a Selected List of Star Names", Popular Astronomy 52 (3): 12, Bibcode:1944PA.....52....8D
  10. ↑ Allen, R. H. (1963), Star Names: Their Lore and Meaning (Reprint ed.), New York: Dover Publications Inc, p. 52, ISBN 0-486-21079-0, retrieved 2010-12-12.
  11. ↑ γ Aqr as Aoul al Achbiya or Prima Tabernaculorum (the first of luck of the homes or tents), π Aqr as Wasat al Achbiya or Media Tabernaculorum (the middle of luck of the homes or tents) and ζ Aqr as Achr al Achbiya or Postrema Tabernaculorum (the end of luck of the homes or tents). η Aqr should be designated as al Achbiya consistently, but it was not designated as the Arabic name except the name Hydria (Greek) or Deli (Hebrew)
  12. ↑ (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.
  13. ↑ (Chinese) 香港太空館 - 研究資源 - 亮星中英對照表, Hong Kong Space Museum. Accessed on line November 23, 2010.
  14. ↑ King, J. R. (July 1994), "Accretion from Circumstellar Discs and the Lambda-Bootis Phenomenon", Monthly Notices of the Royal Astronomical Society 269 (1): 209, Bibcode:1994MNRAS.269..209K, doi:10.1093/mnras/269.1.209.
  15. ↑ "The Colour of Stars", Australia Telescope, Outreach and Education (Commonwealth Scientific and Industrial Research Organisation), December 21, 2004, retrieved 2012-01-16.

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