Sigma Aquarii

From Wikipedia, the free encyclopedia
Jump to navigation Jump to search

Sigma Aquarii
Diagram showing star positions and boundaries of the Aquarius constellation and its surroundings
Cercle rouge 100%.svg
Location of σ Aquarii (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Aquarius
Right ascension  22h 30m 38.81546s[1]
Declination –10° 40′ 40.6238″[1]
Apparent magnitude (V) 4.81[2]
Spectral type A0 IVs[3]
U−B color index –0.14[2]
B−V color index –0.08[2]
Radial velocity (Rv)+11[4] km/s
Proper motion (μ) RA: +0.30[1] mas/yr
Dec.: –26.87[1] mas/yr
Parallax (π)11.26 ± 1.26[1] mas
Distanceapprox. 290 ly
(approx. 89 pc)
Absolute magnitude (MV)0.29±0.23[5]
Mass2.87[6] M
Radius2.87[5] R
Luminosity105[6] L
Surface gravity (log g)4.07[7] cgs
Temperature10,115[6] K
Metallicity [Fe/H]+0.44[7] dex
Rotational velocity (v sin i)21[8] km/s
Age30[5] Myr
Other designations
57 Aquarii, BD–11 5850, FK5 1591, HD 213320, HIP 111123, HR 8573, SAO 165134.[9]
Database references

Sigma Aquarii (σ Aqr, σ Aquarii) is the Bayer designation for a double star in the equatorial constellation of Aquarius. It is visible to the naked eye with an apparent visual magnitude of 4.81.[2] Based upon parallax measurements, the distance to this star is roughly 290 light-years (89 parsecs).[1]

Sigma Aquarii has a stellar classification of A0 IVs,[3] indicating that it is a subgiant star; the s qualifier indicates that its absorption lines are sharp (narrow) in comparison with standard stars, caused by relatively slow rotation. It has been categorized as a hot Am star,[10] meaning that it is a chemically peculiar, although this is now considered doubtful;[11] the spectrum displays at least double the normal abundances of elements like magnesium, aluminum and silicon, while helium and scandium are under-abundant. Calcium, normally deficient in Am stars, is has near-normal abundance.[10]

The Hipparcos catalogue identified Sigma Aquarii as a possible astrometric binary with an orbital period of 654 days.[12]


  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.
  2. ^ a b c d Johnson, H. L.; et al. (1966), "UBVRIJKL photometry of the bright stars", Communications of the Lunar and Planetary Laboratory, 4 (99): 99, Bibcode:1966CoLPL...4...99J.
  3. ^ a b 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, R. E. (1953), "General Catalogue of Stellar Radial Velocities", Washington, Carnegie Institute of Washington D.C., Bibcode:1953GCRV..C......0W.
  5. ^ a b c Gerbaldi, M.; et al. (June 1999), "Search for reference A0 dwarf stars: Masses and luminosities revisited with HIPPARCOS parallaxes", Astronomy and Astrophysics Supplement, 137 (2): 273–292, Bibcode:1999A&AS..137..273G, doi:10.1051/aas:1999248.
  6. ^ a b c Zorec, J; Royer, F (2012). "Rotational velocities of A-type stars. IV. Evolution of rotational velocities". Astronomy & Astrophysics. 537: A120. arXiv:1201.2052. Bibcode:2012A&A...537A.120Z. doi:10.1051/0004-6361/201117691.
  7. ^ a b Gebran, M; Farah, W; Paletou, F; Monier, R; Watson, V (2016). "A new method for the inversion of atmospheric parameters of A/Am stars". Astronomy & Astrophysics. 589: A83. arXiv:1603.01146. Bibcode:2016A&A...589A..83G. doi:10.1051/0004-6361/201528052.
  8. ^ Royer, F; Zorec, J; Gómez, A. E (2007). "Rotational velocities of A-type stars. III. Velocity distributions". Astronomy and Astrophysics. 463 (2): 671. arXiv:astro-ph/0610785. Bibcode:2007A&A...463..671R. doi:10.1051/0004-6361:20065224.
  9. ^ "* sig Aqr". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2012-07-04.
  10. ^ a b Adelman, S. J.; Young, J. M.; Baldwin, H. E. (February 1984), "Optical region elemental abundance analyses of B and A stars. II - The hot AM stars Omicron Pegasi and Sigma Aquarii and the marginal peculiar A star Nu CANCRI", Monthly Notices of the Royal Astronomical Society, 206 (3): 649–660, Bibcode:1984MNRAS.206..649A, doi:10.1093/mnras/206.3.649.
  11. ^ Renson, P; Manfroid, J (2009). "Catalogue of Ap, Hg Mn and Am stars" (PDF). Astronomy and Astrophysics. 498 (3): 961. Bibcode:2009A&A...498..961R. doi:10.1051/0004-6361/200810788.
  12. ^ Perryman, M. A. C.; Lindegren, L.; Kovalevsky, J.; Hoeg, E.; et al. (July 1997). "The HIPPARCOS Catalogue". Astronomy and Astrophysics. 323: L49–L52. Bibcode:1997A&A...323L..49P. Note about binarity

External links[edit]