Sigma Aquarii

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
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]
Characteristics
Spectral type A0 IVs[3]
U−B color index –0.14[2]
B−V color index –0.08[2]
Astrometry
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]
Details
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
SIMBADdata

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, has near-normal abundance.[10]

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

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.
  2. 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. 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. 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. 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. 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. 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
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