106 Aquarii

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106 Aquarii
Diagram showing star positions and boundaries of the Aquarius constellation and its surroundings
Cercle rouge 100%.svg
Location of 106 Aquarii (circled)[1]
Observation data
Epoch J2000.0 (ICRS)      Equinox J2000.0 (ICRS)
Constellation Aquarius
Right ascension 23h 44m 12.07893s[2]
Declination –18° 16′ 36.9688″[2]
Apparent magnitude (V) +5.244[3]
Spectral type B9 V[4]
U−B color index –0.239[3]
B−V color index –0.086[3]
Radial velocity (Rv) +14.0[5] km/s
Proper motion (μ) RA: +27.23[2] mas/yr
Dec.: –2.94[2] mas/yr
Parallax (π) 8.61 ± 0.54[2] mas
Distance 380 ± 20 ly
(116 ± 7 pc)
Radius 2.7–3.2[6] R
Rotational velocity (v sin i) 370[7] km/s
Other designations
BD–19 6500, FK5 1621, HD 222847, HIP 117089, HR 8998, SAO 165854.[8]
Database references

106 Aquarii (abbreviated 106 Aqr) is a star in the equatorial constellation of Aquarius. 106 Aquarii is the Flamsteed designation, although it also bears the Bayer designation i1 Aquarii. It has an apparent visual magnitude of +5.2,[3] making it bright enough to be viewed from the suburbs according to the Bortle Dark-Sky Scale. An annual parallax shift of 8.61[2] milliarcseconds yields an estimated distance of around 380 light-years (120 parsecs) from Earth.

The spectrum of this star fits a stellar classification of B9 V,[4] indicating this is a B-type main sequence star. It is spinning rapidly with a projected rotational velocity of 370 km/s.[7] X-ray emission with a luminosity of 6.0 × 1029 erg s−1 has been detected from this star. This is unusual since a B-type star normally does not have any significant X-ray emission. Instead, it may have an undetected lower mass companion.[9]


  1. ^ Of the grouping of four stars within the circle, 106 Aquarii is the second from the left per:
    Sinnott, Roger W.; et al. (1997), Millennium Star Atlas, 3, Sky Publishing Corporation and the European Space Agency, p. 1351, ISBN 0-933346-82-4. 
  2. ^ 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:0708.1752Freely accessible, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357. 
  3. ^ a b c d Gutierrez-Moreno, Adelina; et al. (1966), A System of photometric standards, 1, Publicaciones Universidad de Chile, Department de Astronomy, pp. 1–17, Bibcode:1966PDAUC...1....1G. 
  4. ^ 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, Bibcode:1988mcts.book.....H. 
  5. ^ Wielen, R.; et al. (1999), Sixth Catalogue of Fundamental Stars (FK6). Part I. Basic fundamental stars with direct solutions (35), Astronomisches Rechen-Institut Heidelberg, Bibcode:1999VeARI..35....1W. 
  6. ^ Pasinetti Fracassini, L. E.; et al. (February 2001), "Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS) - Third edition - Comments and statistics", Astronomy and Astrophysics, 367: 521–524, arXiv:astro-ph/0012289Freely accessible, Bibcode:2001A&A...367..521P, doi:10.1051/0004-6361:20000451. 
  7. ^ a b Royer, F.; et al. (February 2007), "Rotational velocities of A-type stars. III. Velocity distributions", Astronomy and Astrophysics, 463 (2): 671–682, arXiv:astro-ph/0610785Freely accessible, Bibcode:2007A&A...463..671R, doi:10.1051/0004-6361:20065224. 
  8. ^ "106 Aqr -- Star", SIMBAD, Centre de Données astronomiques de Strasbourg, retrieved 2012-07-15. 
  9. ^ Hubrig, S.; et al. (June 2001), "Search for low-mass PMS companions around X-ray selected late B stars", Astronomy and Astrophysics, 372: 152–164, arXiv:astro-ph/0103201Freely accessible, Bibcode:2001A&A...372..152H, doi:10.1051/0004-6361:20010452. 

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