Omega2 Aquarii

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Omega2 Aquarii
Diagram showing star positions and boundaries of the Aquarius constellation and its surroundings
Cercle rouge 100%.svg
Location of ω2 Aquarii (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Aquarius
Right ascension  23h 42m 43.34473s[1]
Declination –14° 32′ 41.6523″[1]
Apparent magnitude (V) 4.49[2]
Spectral type B9 V[3]
U−B color index –0.12[2]
B−V color index –0.04[2]
Radial velocity (Rv)+3[4] km/s
Proper motion (μ) RA: +99.28[1] mas/yr
Dec.: –66.32[1] mas/yr
Parallax (π)21.96 ± 0.26[1] mas
Distance149 ± 2 ly
(45.5 ± 0.5 pc)
Absolute magnitude (MV)+1.20[5]
Radius1.94 ± 0.06[6] R
Luminosity37[5] L
Surface gravity (log g)4.22 ± 0.03[6] cgs
Temperature10,504 ± 91[6] K
Rotational velocity (v sin i)148[7] km/s
Other designations
ω2 Aqr, 105 Aquarii, BD–15 6476, FK5 894, GJ 9836, HD 222661, HIP 116971, HR 8988, SAO 165842.[8]
Database references

Omega2 Aquarii, Latinized from ω2 Aquarii, is the Bayer designation for a triple star[9] system in the equatorial constellation of Aquarius. It can be seen with the naked eye, having an apparent visual magnitude of 4.49.[2] The approximate distance to this star, 149 light-years (46 parsecs), is known from parallax measurements taken during the Hipparcos mission.[1]

The primary component of this system is a massive, B-type main sequence star with a stellar classification of B9 V.[3] This star has nearly double the radius of the Sun[6] and is spinning rapidly with a projected rotational velocity of 148 km/s.[7] The outer atmosphere has an effective temperature of 10,504 K,[6] giving it the blue-white hue of a B-type star.[10]

There is a close orbiting stellar companion of unknown type, with a third component at an angular separation of 5.7 arcseconds. The latter is a K-type main sequence star with a visual magnitude of 9.5.[9] This system is among the 100 strongest stellar X-ray sources within 163 light-years (50 pc) of the Sun. It is emitting an X-ray luminosity of 1.2 × 1030 erg s−1.[11]


  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 Nicolet, B. (1978), "Photoelectric photometric Catalogue of homogeneous measurements in the UBV System", Astronomy and Astrophysics Supplement Series, 34: 1–49, Bibcode:1978A&AS...34....1N.
  3. ^ a b Houk, Nancy (1978), Michigan catalogue of two-dimensional spectral types for the HD stars, 4, Ann Arbor: Dept. of Astronomy, University of Michigan,
  4. ^ Wilson, Ralph Elmer (1953), General Catalogue of Stellar Radial Velocities, Washington: Carnegie Institution of Washington, Bibcode:1953GCRV..C......0W.
  5. ^ a b 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.
  6. ^ a b c d e Fitzpatrick, E. L.; Massa, D. (March 2005), "Determining the Physical Properties of the B Stars. II. Calibration of Synthetic Photometry", The Astronomical Journal, 129 (3): 1642–1662, arXiv:astro-ph/0412542, Bibcode:2005AJ....129.1642F, doi:10.1086/427855.
  7. ^ a b 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.
  8. ^ "105 Aqr -- Star in double system", SIMBAD, Centre de Données astronomiques de Strasbourg, retrieved 2008-05-16.
  9. ^ 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.
  10. ^ "The Colour of Stars", Australia Telescope, Outreach and Education, Commonwealth Scientific and Industrial Research Organisation, December 21, 2004, retrieved 2012-01-16.
  11. ^ Makarov, Valeri V. (October 2003), "The 100 Brightest X-Ray Stars within 50 Parsecs of the Sun", The Astronomical Journal, 126 (4): 1996–2008, Bibcode:2003AJ....126.1996M, doi:10.1086/378164.

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